~ United States 'I. . 

: ~ Department of 

Agriculture 

Forest Service 

Southern Forest 

Experiment 

Station 

New Orleans, 

Louisiana 

General Technical 

Report 

SO-96 

September 1993 

Ash Pests 

A Guide to MaJor 

I,nsects, Diseases, 

Air Pollution Injury, 

and Chemical Injury 

J. D. Solomon, T. D. Leininger, A. D. Wilson, 

R. LAndernon, L C. Thompson, and 

F. I. McCracken 
ACKNOWLEDGMENTS 

We are grateful to the following individuals for reviewing the manuscript: (insect section) M.o. Harrell, University of Nebraska, lIncoln, 

NE; R. C. Morris (retired), USDA Forest Service, Cherokee Village, AR; C. 

E. Palm, L. P. Abrahamson, and D. C. Allen, State University of New York, 

Syracuse, NY; (disease section) S. C. Redlin, USDA APHIS, Hyattsville, 

MD; W. A. Sinclair, Cornell University, Ithaca, NY; and J. A. Walla, North 

Dakota State University, Fargo, ND. Special thanks go to P. Mistretta, 

USDA Forest Service, Forest Pest Management, Atlanta, GA, for 

assistance with the pesticide section. 

Our appreciation is extended to the following agencies or individuals for 

photographs or specimens for making photographs of some pests: Great 

Lakes Forest Centre, Sault Ste. Marie, Ontario (spring cankerworm, fall 

webworm, ashleaf gall mite); M. 0. Harrell, University of Nebraska, Lincoln, NE (oystershell scale); A. Tagestad, North Dakota Forest Service, 

Bottineau, ND (ash bark beetles); J. A. Walla, North Dakota State University, Fargo, ND (Laetiporus sulphureus, Perenniporia fraxinophila, ash 

anthracnose, Mycosphaerella leaf spot); C. L. Ash, University of Minnesota, St. Paul, MN (Verticillium wilt, powdery mildew); Florida Department of Agriculture and Consumer Services, Tallahassee, FL (ash rust); P. 

T. Marshall, Indiana Dept. of Natural Resources, Vallonia, IN 

(Mycosphaerella leaf spot, ash yellows); M. E. Mielke, USDA Forest Service, St. Paul, MN (ozone, ash rust); S. C. Redlin, USDA APHIS, Hyattsville, MD (anthracnose); and W. A. Sinclair, Cornell University, Ithaca, 

NY (ash yellows, ash dieback). 

We also thank T. H. Filer (retired), USDA Forest Service, Greenville, MS, 

and C. J. Luley (previously with Missouri Department of Conservation), 

Rochester, NY, for their help with early drafts of the manuscript; L. 

Newsome and W. B. Smyly, USDA Forest Service, Stoneville, MS, for 

assistance in collecting, preparing, and studying the pests; and A. S. 

Risner, USDA Forest Service, Stoneville, MS, for typing the manuscript. 

This publication was produced in cooperation with USDA Fo~ 

est Service, Southern Region, State and Private Forestry, Forest 

Pest Management. 
CONTENTS 

INTRODUCTION ................................... " . . .. 1 

FOLIAGE INSECTS ..................................... 3 

BlackheadedAshSavvfly ... . .... . ....................... 3 

Brovvnheaded Ash Savvfly . . .......... . .................. 3 

Spiny Ash Savvfly . . ... . ......... . . . . . ............ . ..... 3 

Ash Sphinx . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 4 

Great Ash Sphinx .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 4 

Waved Sphinx ....... . .. . ............. . .... . ....... . ... 4 

Ash Plant Bugs .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5 

Woolly Ash Aphid ...................................... 6 

TERMINAL, TWIG, AND BRANCH INSECTS. . . . . . . . . . . . . . 7 

Ash Borer (terminal borer) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 7 

European Fruit Lecanium ... . ........ . .. . .............. 8 

Oystershell Scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 8 

White Peach Scale ...... . ... . ............. .. ........... 8 

Flatid Planthoppers ..... .. . . ..... . . .. ............... . .. 9 

INSECT BORERS, MINERS, AND BARK BEETLES 

Ash Borer (trunk borer) ......... . ... . ................... 10 

Banded Ash Clearvving ................................. 11 

Carpentervvorm . . ................ . ..................... 12 

Banded Ash Borer ......... . ............... . . . ......... 13 

Redheaded Ash Borer ............... . .................. 13 

Ash Cambium Miner .................. . ...... . ...... . .. 14 

Eastern Ash Bark Beetle ............ . .................. 15 

Northern Ash Bark Beetle .............................. 15 

White-Banded Ash Bark Beetle ...... . ................... 15 

FLOWER AND SEED INSECTS AND MITES 

Ash Flovvergall Mite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 

Ash Seed Weevils .................... . ................. 17 

MINOR INSECTS AND MITES 

Leafroll Midges ........................................ 18 

Leaf Beetle ..... . ........ . ........ . .................... 18 

Spring Cankervvorm .................................... 18 

Fall Webvvorm ......................................... 18 

Forest Tent Caterpillar ......... . ....................... 18 

Ashleaf Gall Mite ...................................... 19 

SEEDLING DISEASES 

Damping-Off ............... . .......................... 20 

LEAF DISEASES 

Anthracnose ................ ' .' ......................... 21 

Ash Rust .............................................. 22 

Mycosphaerella Leaf Spots .............................. 23 

Povvdery Mildevvs ...................................... 24 
DECLINES, DIEBACKS, AND WILTS 

Ash Yellows ........................................... 25 

Ash Dieback ........................................... 26 

Verticillium Wilt ....................................... 27 

CANKERS 

Fusicoccum Canker .................................... 28 

Nectria Canker ........................................ 29 

DECAYS 

BUTT ROTS .... . .................. . .................. 30 

Varnish Fungus Rot ................................. 31 

Sulfur Fungus Rot .................................. 32 

STEM ROTS ................................ . ......... 33 

Perenniporia Stem Rot ............................... 33 

TOP ROTS ............................................ 34 

ROOT DISEASES 

Corticium Root Rot .................................... 35 

Texas Root Rot .. . ..................................... 36 

Mushroom Root Rot .................................... 37 

PARASITIC PLANTS 

Mistletoe .............................................. 38 

AIR POLLUTION AND CHEMICAL INJURIES 

Air Pollution Injury .................................... 39 

Chemical Injury ....................................... 39 

PESTICIDES ............................................ 41 

MAINTAINING TREE HEALTH .......................... 43 

GLOSSARY ...................... < •••••••••••••••••••••••• 44 

ii 
Ash Pests 

A Guide to Major Insects, Diseases, 

Air Pollution Injury, and Chemical Injury 

J. D. Solomon, T. D. Leininger, A. D. Wilson, R. L. Anderson, 

L. C. Thompson, and F. 1. McCracken 

INTRODUCTION 

The ashes (Fraxinus spp.) are 

one of our more valuable hardwood 

resources - some 275 million board 

feet of ash lumber are sawn 

annually in the United States. 

White ash (F. americana L.) and 

green ash (F. pennsylvanica Marsh.), 

widely distributed throughout the 

Eastern United States and southern Canada, are the two most 

important species. Black ash (F. 

nigra Marsh.) is an important timber species in the Northeastern 

United States and southeastern 

Canada. Ash wood - tough, strong, 

and resistant to shock - is used for 

handles, oars, baseball bats, and 

furniture. Green, white, and black 

ashes grow best on fertile, moist, 

well-drained soils. But green ash, 

the most adaptable of the ashes, 

grows naturally on a wide range of 

sites from clay soils flooded up to 40 

percent of the time to sandy, dry, 

harsh sites. Because of its hardiness, adaptability, and drought tolerance, green ash is used widely as 

an ornamental, in shelterbelts of 

the Great Plains, and for revegetation of strip-mining spoil banks. 

Green and white ashes are among 

only a few hardwood species being 

used to establish commercial timber plantations. 

Insects, diseases, and pollutants 

are continuing problems for the 

ashes, but few actually threaten 

their widespread use. Disease, simply stated, is a condition of abnormal growth resulting from infection 

by a biotic agent (fungus, bacterium, or virus), or induced by an 

abiotic stress such as drought or air 

pollution. Fungi are the most comJ. D. Solomon is supervisory research entomologist and project leader, T. D. 

Leininger and A. D. Wilson are research plant pathologists, and F. I. McCracken was 

principal research plant pathologist (retired) at Southern Hardwood Laboratory, 

U.S. Department of Agriculture, Forest Service, Southern Forest Experiment Station, Stoneville, MS 38776. In cooperation with: Mississippi Agricultural and Forestry Experiment Station and the Southern Hardwood Forest Research Group. R. L. 

Anderson is field office representative, Southeast Area, U.S. Department of Agriculture, Forest Service, State and Private Forestry, Asheville, NC 28802; L. C. 

Thompson is professor of forest protection, University of Arkansas, Monticello, AR 

71655. 

1 
mon causes of diseases of trees. 

Diminished growth and vigor, 

brought on by one or more biotic or 

abiotic factors, are perhaps the 

most serious problems of white ash. 

Wood boring insects, the most 

damaging pests of green ash, have 

damaged shelterbelt plantings in 

the Great Plains and caused considerable degrade losses in logs and 

lumber in the South. An estimated 

one-third of the ash trees larger 

than pole size contain some heartrot. Seed insects sometimes destroy 

up to 90 percent of the seed crop. 

Insects and diseases that destroy 

f6liage can be disfiguring and cause 

growth loss, but seldom cause widespread damage. Because the gypsy 

moth, Lymantria dispar (L.), rarely 

feeds on ashes, ash species are often 

favored for planting in both forest 

and urban settings in the Northeastern States. 

Cultural practices that maintain 

and promote tree health are 

encouraged to minimize losses. 

Control measures are not always 

feasible or needed for some ash 

pests covered in this guide, 

especially when light infestations or 

infections occur. The best procedure in these cases is to prevent 

problems by promoting and maintaining healthy trees. To this end, 

2 

some recommendations are provided in the back of this guide in a 

section called "Maintaining Tree 

Health." However, chemical controls may become necessary as a 

last resort when all else fails. 

This booklet will help nursery 

workers, resource managers, pest 

control personnel, and homeowners 

to prevent, identify, and control ash 

pests. The major insect and disease 

pests of ashes in the Eastern 

United States are emphasized. 

Descriptions and illustrations of 

the pests and their damage are provided to aid in identification. Brief 

notes are given on their biology and 

control to aid in assessing damage 

and making control decisions. Lists 

of chemical controls are provided, 

but recommendations are subject to 

change as certain compounds are 

discontinued and new materials 

approved. The chemical control section (tear sheet) in this booket can 

be removed and discarded when 

outdated as indicated by registered 

uses on pesticide labels. For further 

information on ' pesticides or additional assistance with ash pests, 

contact your State forester, county 

extension agent, or the nearest 

office of the USDA Forest Service, 

State and Private Forestry, Forest 

Pest Management. 
FOLIAGE INSECTS 

Blackheaded Ash Sawfly, Tethida barda (Say) 

Brownheaded Ash Sawfly, Tomostethus multicinctus (Rohwer) 

Spiny Ash Sawfly, Eupareophora parca (Cresson) 

Importance. - The ash sawflies 

are widely distributed throughout 

eastern North America and westward to the Great Plains. Young 

trees in new plantations and ornamental plantings seem particularly 

susceptible to defoliation. 

Identifying the Insects. - Larvae of the blackheaded (fig. la) and 

brownheaded ash sawflies have 

greenish- to yellowish-white bodies. 

The spiny ash sawfly larvae (fig. Ib) 

have dark heads and gray bodies 

with numerous forked, dark spines. 

Larvae of all these species are about 

16 to 19 mm long at maturity. 

Adults are typical sawflies, with 

mostly black bodies marked with 

red and white, and measure 6 to 8 

mm in length. 

Identifying the Injury. - The 

larvae feed gregariously in groups 

of 4 to 20, often lined up in rows 

feeding side by side. Young larvae 

chew holes in the leaflets, and older 

larvae eat entire leaflets. Heavily 

infested young trees may be completely defoliated in 1 to 2 weeks. 

Older trees may be so ragged 

that most of the leaves drop prematurely. 

Biology. - In the spring, adults 

lay eggs in slits cut along the outer 

margins of young leaflets. Larvae 

feed and mature in early to midMay in the South, later in the 

North. When mature, they drop to 

the ground where they make earthen cocoons in the soil and spend the 

summer, fall, and winter. In the 

spring, larvae pupate and emerge as 

adults to begin the cycle again. 

There is one generation per year. 

Control. - Natural enemies usually keep sawfly densities low. 

Insecticides are effective in young 

plantations and ornamental plantings when severe infestations occur. 

Figure l.-(a) Blackheaded ash sawfly larvae; (b) spiny ash sawfly larvae. 

3 
Ash Sphinx, Manduca jasminearum (Guerin) 

Great Ash Sphinx, Sphinx chersis (Hubner) 

Waved Sphinx, Ceratomia undulosa (Walker) 

Importance. - Sphinx larvae 

are seldom serious pests, but they 

are readily noticed because they are 

large and ornate caterpillars. All 

three species occur in the Eastern 

United States. The great ash sphinx 

ranges from coast to coast and has 

been known to concentrate locally 

on clumps of saplings, young trees, 

and sprouts. 

Identifying the Insects (fig. 

2a). - Sphinx larvae (hornworms) 

become quite large, reaching 75 mm 

in length. They have a distinctive 

horn-shaped spine on their distal 

end. Color markings are mostly pale 

green, usually with diagonal yellow 

or white markings. Adults are large 

moths with stout, spindle-shaped 

bodies; wings are narrow and 

brown or gray with dark and light 

bands. They are very strong fliers 

and are commonly known as hawk 

moths or hummingbird moths. 

Identifying the Injury (fig. 

2b) - Larvae typically consume the 

entire blade of tender leaves; midribs and major veins may be left 

on older leaves. Feeding begins and 

is most noticeable on the young 

leaves of terminals and branch ends 

and progresses toward the older 

foliage. 

Biology. - Adults emerge during 

May and June and lay eggs on the 

foliage. Larvae may be found 

feeding from June to September. 

Mature larvae burrow into the soil 

to pupate. There are two generations per year in the South and only 

one in the North. Overwintering 

occurs in the pupal stage in the 

soil. 

Control. - Natural enemies usually keep hornworm populations in 

check. Insecticides are rarely 

needed to protect seedlings and 

small trees. 

Figure 2.-(a) Sphinx larva (hornworm); (b) feeding injury on young sapling. 

4 
Ash Plant Bugs, Tropidosteptes spp. 

Importance. - Three species of 

ash plant bugs, Tropidosteptes 

amoenus Reuter, T. tricolor Van 

Duzee, and T. cardinalis Uhler, are 

mainly eastern species occurring 

west to Texas and the Great Plains; 

whereas two, T. illitus Van Duzee 

an T. pacificus Van Duzee, are 

western species. They suck the 

juices from buds, leaves, seeds, and 

shoots, causing distortion and premature shedding. 

Identifying the Insects (fig. 

3a). - Adults are elongate-oval, soft 

bodied, 3 to 6 mm long, with 

piercing-sucking mouthparts. They 

vary in color by species from black 

and white, to red and black, to light 

or dark brown. Nymphs are smaller 

than adults and are wingless. 

Identifying the Injury. -

Initial injury is caused mainly by 

the nymphs, which feed on the 

opening buds and new leaves. Later 

instars feed on leaves, flowers, and 

seeds. Concentrated feeding on buds 

and small expanding leaves causes 

them to become discolored, distorted, and stunted (fig. 3b). Feeding on older leaves causes stippling 

with black excrement spots (fig. 3c). 

Biology. - Ash plant bugs overwinter as eggs laid in the thin bark 

of twigs. In the spring, these eggs 

hatch as the buds are opening. 

Nymphs feed mostly on the undersides of leaves and take 4 to 5 weeks 

to reach the adult stage. First generation adults begin the cycle again 

by laying their eggs mainly on the 

midribs of leaves. Typically, two 

broods are produced each year, although T. illitus produces only one. 

Control. - Dormant oil sprays 

have been used during the winter 

months to kill the eggs. Insecticides 

can be used to control nymphs and 

adults in the spring. 

Figure 3.-(a) Adult ash plant bug (Tropidosteptes cardinalis); (b) injury to young 

expanding leaves; (c) stippling injury to full-grown leaves. 

5 
Woolly Ash Aphid, Prociphilus fraxinifolii (Riley) 

Importance. - This aphid occurs 

in the Eastern United States and 

west to Colorado. Heavy aphid 

infestations cause premature defolition and stunt growth. The distorted foliage, along with accompanying honeydew and sooty mold, 

mar the beauty of ornamentals and 

make nursery plants unsalable. 

Identifying the Insects (fig. 

4a). -Aphids are 2.0 to 2.5 mm 

long, soft bodied, and pear shaped 

to globular, with a pair of tubes projecting from the abdomen. They are 

yellowish green to pale yellow with 

ibrown head and legs. Both winged 

and wingless forms occur. White, 

waxy secretions often , cover the 

aphids, giving them a "woolly" 

appearance. 

Identifying the Injury. - Aphids 

suck the sap from the undersides of 

tender, developing leaves of terminals and branch tips (fig. 4b). Feeding causes leaves to curl.downward 

(fig. 4c). Unfolding the tightly 

curled leaves wfll reveal clusters of 

aphids. Heavily infested leaves may 

drop prematurely. A whitish, sticky 

honeydew produced by the aphids 

frequently coats the foliage and 

supports the growth of black, sooty 

mold. 

Biology. - Overwintering occurs 

as eggs in bark crevices. , The eggs 

hatch in the spring into wingless 

females that reproduce without 

mating. Several generations are 

produced each year. During fall, 

winged adults deposit the overwintering eggs. The largest populations 

are usually present during early 

summer. 

Control. - Natural enemies routinely keep most aphid populations 

under control, but insecticides may 

be needed to protect nursery stock 

and ornamentals. 

Figure 4. - (a) Closeup of aphids under curled leaf; (b) heavily infested ash terminal; 

(c) heavily curled leaves caused by aphids. 

6 
TERMINAL, TWIG, AND BRANCH INSECTS 

Ash Borer (terminal borer), Podosesia syringae (Harris) 

Importance. - The ash borer is 

found throughout eastern North 

America. Spring feeding on tender 

shoots causes mortality of terminals resulting in forked trunks. 

When plantations are established 

to produce sawlogs, forked or deformed trunks are unacceptable 

losses. (This insect is also covered 

as a trunk pest in the insect borer 

section.) 

Identifying the Insect. - Tiny 

larvae found burrowing in terminals are white to yellowish with the 

dark gut visible. Larvae vary from 

1.5 to 5.0 mm in length. Mter vacating the shoots, they feed elsewhere 

on the trunk and branches and may 

reach 34 mm in length. Adults are 

brown to reddish clear wing moths 

with a wingspan of 25 to 38 mm. 

Identifying the Injury (fig. 

5a). - The earliest symptom is a 

sudden wilting of succulent green 

shoots, which become shriveled and 

dark within 4 to 8 days (fig. 5b). 

Tunnels are typically 1 to 3 cm long 

before the shoot is vacated. It takes 

less than 1 month for the terminal 

to wilt, darken, shrivel, die, and 

break away, often resulting in forked stems in new growth (fig. 5c). 

Biology. - Adult moths begin 

emerging in March in the South 

and oviposit on the shoots and bark. 

Newly hatched larvae tunnel into 

the succulent shoots during April 

and May. In the South, shoot injury 

peaks by mid-May, declines in late 

May, and ceases by early June. 

Young larvae are present in the 

shoots for only 2 to 3 weeks; then 

they vacate the galleries and become 

trunk borers. 

Control. - Natural enemies help 

reduce borer populations. Insecticides may be necessary in new 

plantings, especially those surrounded by heavily infested ashes. 

Figure 5.-(a) Early symptoms of ash borer infested terminal; (b) terminal killed by 

ash borer; (c) fork resulting from killed terminal. 

7 
European Fruit Lecanium, Parthenolecanium corni (Bouche) 

Oystershell Scale, Lepidosaphes ulmi (L.) 

White Peach Scale, Pseudaulacaspis pentagona (Targioni-Tozzetti) 

Importance. - Scale insects are 

common pests of ashes and are distributed throughout the United 

States. These insects suck the sap 

from plants, weakening them and 

making them susceptible to other 

pests. Scales often kill branches and 

occasionally individual trees. 

Identifying the Insects. - Scale 

insects appear as protrusions on 

the branches and twigs. Mature 

oystershell scales are 3 mm long, 

brownish to purplish gray, narrow, 

and rounded toward the rear with 

concentric bands (fig. 6a). White 

peach scales are 1.5 mm wide, circular, and white to gray or yellowish 

(fig. 6b). European fruit lecaniums 

are 4.7 mm wide, circular, reddish 

to dark brown, and often covered 

with white powder (fig. 6c). 

Identifying the Injury. - Crown 

dieback is the principal symptom of 

severe infestations. Honeydew may 

be produced, which supports a 

black, sooty mold that turns leaves 

and branches black. Heavily infested plants produce pale foliage 

and few new shoots and exhibit twig 

and branch dieback. 

Biology. - Females lay eggs under 

waxy domes. The newly hatched 

nymphs, called crawlers, crawl to 

new sites on the bark and begin 

feeding. The oystershell scale overwinters in the egg stage. '!\vo generations occur in Maryland, where 

crawlers are present in May and 

June and again in mid-July. The 

white peach scale has four generations per year in Florida and three 

in Maryland. The crawlers are present in May, July, late August, and 

early September. The European 

fruit lecanium produces one generation per year. 

Control. - Contact insecticides 

are effective when timed with the 

appearance of crawlers. Dormant 

oil sprays will kill overwintering 

scales. 

Figure 6.-(a) Oystershell scales; (b) white peach scales; (c) European fruit 

lecaniums. 

8 
Flatid Planthoppers: Acanalonia conica (Say), Anormenis septentrionalis (Spinola), Metcalfa pruinosa (Say) 

Importance. - Flatid planthoppers occur throughout the Eastern 

United States, west to the Great 

Plains; one species, Metcalfa pruinosa, ranges from coast to coast. 

Planthoppers suck the sap from 

small diameter stems, but damage 

is usually minor. Oviposition injuries sometimes kill seedlings. 

Identifying the Insects (fig. 

7 a). - Adult flatid planthoppers are 

pale or yellowish green to brown or 

black but are usually covered by 

white, powdery wax, which imparts 

a whitish-gray or bluish-green 

appearance. They have large prominent wings held at an acute, rooflike 

angle over the body and range from 

6 to 13 mm long. Nymphs are wingless, slightly elongate, slightly flattened, and partially to completely 

covered with filaments of white, 

woollike wax (fig. 7b). 

Identifying the Injury. - Feeding by large populations causes 

seedlings and terminals of older 

plants to wilt. Although sap-feeding 

may slow plant growth, it rarely 

causes widespread die back. However, clusters of oviposition punctures along stems may cause mortality of seedlings and shoot dieback on older plants. 

Biology. - Overwintering eggs 

hatch during the spring. Nymphs 

feed singly or in clusters on tender 

shoots. Adult flatid planthoppers 

appear by June or July and are present until fall. They deposit their 

eggs in a series of short slits in the 

bark. There is only one generation 

per year. 

Control. - Natural enemies help 

keep populations in check. On 

young plants, pruning and destroying shoots that contain oviposition 

punctures (before the eggs are able 

to hatch) provides some control. 

Figure 7.-(a) Adult fiatid planthoppers; (b) fiatid planthopper nymphs. 

9 
INSECT BORERS, MINERS, AND BARK BEETLES 

Ash Borer (trunk borer), Podosesia syringae (Harris) 

Importance. - This borer is a 

destructive pest throughout eastern North America. Trunk infestation rates of 50 percent are common 

in shelterbelts of the Great Plains. 

In the South, trees intended for 

wood products are degraded and 

reduced in value. Shade and ornamental trees may be scarred, seriously weakened, or killed. 

Identifying the Insect. - Adults 

are clearwing moths that mimic 

paper wasps in appearance and 

flight. The wingspan of the moth is 

about 25 mm. The wings and body 

are brownish black, and the legs are 

marked with black, orange, and 

yellow. Larvae are white, except for 

an amber-colored head and thoracic 

shield, and are about 25 to 34 mm 

long at maturity. 

Identifying the Injury (fig. 

8a). - The first evidence of attack is 

sap mixed with fine frass oozing 

from small holes in the bark. Later, 

the frass is extruded in small 

clumps. Circular adult exit holes, 

often with pupal skins protruding, 

are found above the irregularly 

shaped entrance holes. Infestation 

is greatest in the lower trunk. Lumber sawn from infested trees may 

exhibit numerous dark-stained, 

pencil-sized holes (fig. 8b). 

Biology. - Adults begin emerging during February in Florida and 

during July in the North. Emergence is completed by the end of 

July. There is a single brood per 

year. Eggs, deposited singly or in 

small clusters in bark crevices, 

hatch in 11 days. Young larvae mine 

in the phloem and cambium, then 

excavate galleries 7.5 to 13.0 cm 

long in the wood. 

Control. - Natural enemies, 

wound prevention, brood tree 

removal, burlap trunk wraps, and 

insecticides help to reduce populations. Pheromone traps are used to 

monitor moth flights in order to 

time insecticide applications. 

Figure 8. - (a) Ash borer gallery, entrance and exit holes, and bark scars of entrance 

and exit holes; (b) ash borer defects in lumber. 

10 
Banded Ash Clearwing, Podosesia aureocincta Purrington & Nielson 

Importance. - This clearwing is 

similar in distribution and appearance to the ash borer and causes 

similar damage to boles and 

branches. Its populations are 

smaller and more scattered than 

those of the ash borer. 

Identifying the Insect (fig. 

9a). - Adult clear wings are slightly 

larger than adult ash borers and 

have forewings that are violet 

brown and mostly dark. The body is 

brownish black, but abdominal segment 4 is bordered at the rear with 

a distinct, narrow, upward-tapering, bright orange-yellow band. The 

larvae can be distinguished from 

ash borer larvae because they have 

fewer crochets on the abdominal 

legs (12 to 16 per row vs. 16 to 20 

per row, respectively). 

Identifying the Injury (fig. 

9b). - Injury is similar to that of the 

ash borer, but the seasonal occurrence is markedly different. 

Females lay eggs in late summer. 

Soon after, and continuing into the 

fall, larvae begin feeding, causing 

sap to ooze and fine frass to be 

extruded from attack sites. The 

next spring and summer, the frass 

becomes coarse and granular and is 

extruded in small clumps (fig. 9c). 

Pupal skins may be found protruding from exit holes in the bark from 

late summer to winter. 

Biology. - Adults emerge from 

August to December, whereas those 

of the ash borer emerge during 

spring and summer. Emergence 

peaks from mid-September to early 

October. Larvae overwinter as second instars within their mines in 

the phloem-cambium area. 

Control. - Woodpeckers, other 

natural enemies, and good cultural 

practices help to reduce populations. Insecticides must be applied 

in late summer and fall to kill newly 

hatched larvae. 

Figure 9.-(a) Mating pair o{banded ash clearwings; (b) partially completed gallery; (c) entrance. hole in bark with {rass clumps. 

11 
Carpenterworm, Prionoxystus robiniae (Peck) 

Importance. - Carpenterworms, 

widely distributed through the 

United States and southern Canada, bore into trunks and branches. 

For years, they were recognized 

mainly as pests of shade, ornamental, and shelterbelt trees, but their 

impact through log and lumber 

defects is even more important. 

Identifying the Insect (fig. 

lOa). - Young larvae are reddish 

pink. Mature larvae are creamy 

white with a shiny, dark-brown 

head and black mandibles, and are 

50 to 75 mm long. Adults are large, 

grayish moths with black and gray 

mottled wings; males have an 

orange spot on their hind wing. 

Identifying the Injury. - The 

earliest signs of attack are sap spots 

with fine boring dust. Later, frass is 

discharged from entrance holes. 

Larvae chew cavelike burrows 50 

mm in diameter (fig. lOb) and galleries 12 to 22 cm long in the wood 

(fig. lOc). Oval to irregularly shaped 

bark scars are evident. Damage in 

sawn lumber appears as pockets of 

ingrown bark and stained holes 12 

mm in diameter. 

Biology. - Adult moths appear 

from April to June and deposit 400 

to 800 eggs in bark crevices. Eggs 

hatch in 10 to 12 days, and young 

larvae tunnel into the bark and 

wood. Pupation occurs within the 

tunnel and lasts 3 weeks. A life cycle 

requires 1 to 2 years in the South, 

and 2 to 4 years in the North. 

Control. - Open-grown trees are 

most susceptible, thus stands 

should be kept well stocked. Brood 

trees should be identified and 

removed. Injuries during logging 

should be prevented or minimized. 

Natural enemies provide some help. 

Insecticides can protect ornamental 

trees. 

Figure 10.-(a) Carpenterworm larva; (b) large, cave-type burrow under bark; 

(c) gallery in bole. 

12 
Banded Ash Borer, Neoclytus caprea (Say) 

Redheaded Ash Borer, Neoclytus acuminatus (Fabricius) 

Importance. - These borers 

infest weakened, dying, and recEmtly dead ash trees, but are most 

destructive to recently cut sawlogs. 

They occur throughout most of the 

United States, but are most common in the East. 

Identifying the Insects (fig. 

lla). - Adults of both species are 

elongate, tapered in form, and vary 

from 4 to 18 mm in length. The 

redheaded ash borer is reddish with 

yellow bands; the banded ash borer 

is black with yellowish-white bands. 

Larvae of both species are creamy 

white, short, robust, and 10 to 22 

mm long. 

Identifying the Injury (fig. 

llb). - Round adult exit holes in the 

bark and wood and mines under the 

bark are evidence of infestation (fig. 

llc). The principal injury is from 

larval tunnels in the sapwood; the 

oval tunnels are tightly packed with 

frass. Injury to recently felled trees 

and logs is often confined to the 

shaded bottom half. 

Biology. -Adults of the redheaded ash borer emerge from May 

to August in the North and from 

February to November in the 

South. Eggs, deposited under the 

bark, hatch in 1 week. Larvae penetrate the sapwood to feed and overwinter in their tunnels. There are 

two to three generations per year in 

the South and one to two in the 

North. The banded ash borer has 

one generation per year. 

Control. - Keeping ornamentals 

healthy will help prevent infestation. Sawlogs may become infested 

within 20 days of felling during the 

summer and must be processed 

promptly. 

Figure 11. - (a) Adult of redheaded ash borer; (b) cross section of oval, frass-packed 

tunnels; (c) larval mines and exit holes on sapwood surface. 

13 
Ash Cambium Miner, Phytobia sp. 

Importance. - Maggots of this 

fly mine in the cambium of tree 

boles and roots in the Eastern 

United States. They cause defects 

consisting of small, light to dark 

streaks evident in tangential cuts of 

wood or specks known as pith ray 

flecks, worm tracks, or glassworms 

as seen in cross-sectional cuts. Such 

defects cause quality degrade when 

the wood is used for veneer, cabinets, baseball bats, or tool handles. 

Identifying the Insects (fig. 

12a). - The larvae are long, narrow 

maggots, somewhat laterally flattened, and measure about 25 mm 

long when fully grown. Adults look 

somewhat like small, hairy house · 

flies. 

Identifying the Injury (fig. 

12b). - The maggots make long 

threadlike mines in the cambium of 

branches, boles, and roots. Mines 

are most common in the basal 90 

cm of the trunk and in the roots 

within 1.5 m of the bole (fig. 12c). 

Mining in living trees is detectable 

only by removing the bark. In lumber and veneer, mines appear as 

zigzag tracks lighter or slightly 

darker than the natural wood. 

Biology. - Eggs are laid in small 

twigs. Maggots mine in the cambium and inner bark down the stem 

and into the roots. Second-instar 

maggots overwinter in the roots. 

Full-grown maggots exit through 

the bark and form puparia in the 

soil. In the North, pupation occurs 

in May and June, whereas in Mississippi, it occurs from February to 

April. The life cycle is completed in 

1 year. 

Control. - Dead maggots have 

been found in their mines following 

unusually cold winters. Other natural controls are unknown, and 

direct controls have not been 

investigated. 

Figure 12.-(a) Ash cambium miner larva; (b) zigzag glass worm tracks in ash 

veneer; (c) threadlike mines on sapwood surface. 

14 
Eastern Ash Bark Beetle, Hylesinus aculeatus (Say) 

Northern Ash Bark Beetle, Hylesinus criddlei Swaine 

White-Banded Ash Bark Beetle, Hylesinus fasciatus (LeConte) 

Importance. - One or more species of ash bark beetles are found in 

any given region of the United 

States. They attack and breed in 

weakened, felled, and stormdamaged trees; only occasionally do 

they attack healthy trees. On some 

sites of the dry Great Plains, the 

western ash bark beetle causes 

severe branch- and top-kill. 

Identifying the Insects (fig. 

13a). - Adult beetles are slightly 

elongate, cylindrical, and 2.0 to 3.4 

mm long. Dense areas of light- and 

dark-colored scales produce mixed 

bands or spots. Larvae are legless 

grubs with a white, slightly curved 

body and a light-brown head (fig. 

13b). 

Identifying the Injury (fig. 

13c). - Injury to trees results from 

tunneling in the inner bark and surface of the sapwood. The large egg 

gallery has two branches extending 

across the wood grain in opposite 

directions from the bark entrance. 

Larval galleries radiate outward 

from the egg gallery. The bark may 

be peppered with 1-mm, round exit 

holes (fig. 13d). 

Biology. - Overwintering adults 

fly to susceptible trees in the spring 

where they burrow into the bark 

and begin laying eggs. Larvae 

pupate in small cells at the end of 

their tunnels. New adults burrow 

out to the bark surface. There are 

one to two generations per year. 

Adults overwinter in short feeding 

tunnels in the bark of living or 

recently felled trees. 

Control. - Direct controls are 

rarely needed. Cultural controls 

include debarking felled trees and 

logs and/or burning them to prevent 

brood emergence. To prevent 

attacks insecticides may be applied 

to the bark. 

Figure l3.-(a) Eastern ash bark beetle; (b) larvae in galleries; (c) horizontal egg 

galleries with vertical larval galleries; (d) adult exit holes. 

15 
FLOWER AND SEED INSECTS AND MITES 

Ash Flowergall Mite, Aceria fraxiniflora Felt 

Importance. - This eriophyid 

mite attacks male flower clusters, 

turning them into masses of lumpy, 

distorted galls. Infestations do little 

damage to trees, but the galls are 

unsightly and may markedly detract 

from the appearance of ornamentals. The mite is distributed 

throughout the United States and 

southern Canada. 

Identifying the Mite. - The 

mites are minute, about 0.5 mm 

long, soft bodied, wormlike or spindle shaped, and white to straw colored. They are so small as to be 

largely invisible to the unaided eye 

and are frequently overlooked, even 

with a lOx magnifier. 

Identifying the Injury (fig. 14).-

Feeding by the mites on the male 

flower clusters causes swelling of 

the tissues. Flower stems elongate, 

pedicles of individual flowers often 

fuse, and all parts curl and twist. 

Infested flower clusters become 

irregularly branched, fringed, galllike masses. Galls are initially green 

but darken and become black later 

in the season, and many persist 

until the following spring. 

Biology. - In the spring, overwintering females move to the 

developing flowers to feed and 

deposit eggs. Nymphs live and feed 

in protected crevices of the gall 

tissue. There are several generations during the spring and summer. In the fall, fertilized females 

move to bark crevices and beneath 

bud scales to overwinter. 

Control. - High-valued trees can 

be sprayed in the early spring as 

soon as they begin to flower. 

Figure 14. -Male flower clusters converted to gall-like masses by ash flower gall 

mites. 

16 
Ash Seed Weevils, Lignyodes spp. 

Importance. - Three ash seed 

weevils, Lignyodes bisclwffi (Blatchley), L. helvolus (LeConte), and L. 

horridulus (Casey), occur throughout the United States and Canada. 

These weevils feed on the seeds of 

ashes and lilac. Over 60 percent of 

the ash seeds in the Northeastern 

States and up to 95 percent in the 

Great Plains may be destroyed. 

Identifying the Insects (fig. 

15a). - Adults are elongate-oval and 

2.3 to 4.0 mm long. The pronotum 

is narrower than the base of the 

elytra, and the snout is curled with 

elbowed antennae. The pronotum 

and elytra are covered with brown 

to yellow scales. Color patterns distinguish the species. Larvae · are 

white and legless with a curved 

body and brown head (fig. 15b). 

Identifying the Injury.-

Infested seeds are difficult to distinguish with the naked eye. With 

magnification, small, raised, puncture marks partially covered with 

dark excrement can be observed on 

the seedcoat (fig. 15c). Cutting open 

the seed will reveal the feeding larvae 

(fig. 15d). Small oval to irregular 

holes are left in seeds by emerging 

larvae. 

Biology. - The weevils overwinter as larvae in the soil or in fallen 

seeds. Pupation occurs in the soil 

during spring and summer and 

lasts about 12 days. Adults emerge 

during July and August and are 

present until autumn. Females 

deposit eggs singly within the seed 

and seal the openings with excrement. Eggs hatch in 2 days, and the 

larvae completely consume the seed 

contents. Mature larvae exit the 

seed during fall, winter, or spring 

and burrow into the soil to pupate. 

There is one generation per year. 

Control. - Natural controls keep 

most populations in check. Direct 

controls are rarely justified. 

Figure 15.-(a) Adult ash seed weevil; (b) ash seed weevil larva; (c) infested ash 

seeds with egg punctures; (d) seeds cut open to expose larvae. 

Ii 
MINOR INSECTS AND MITES 

Leafroll Midges 

Pest. - Leafroll midges, Dasineura spp.; larvae are small, white 

maggots 2 to 3 mm long; occur in 

the Eastern United States; produce 

one to two generations per year. 

Injury. - Several tiny maggots 

feed together in young, unfolded 

leaves of ashes in early spring, etching the tender epidermis and keeping the leaves from unfolding; 

damaged leaves roll, curl, distort, 

and may falloff (fig. 16a). 

Prevention and Control.-

Natural control is usually adequate; 

trees shoul~ be kept in vigorous 

condition; direct controls are rarely 

needed. 

Leaf Beetle 

Pest. - Leaf beetle, Octotoma 

plicatula (Fab.); a black, wedgeshaped beetle 4 to 5 mm long, with 

a distinctive, irregular design of 

ridges on its wing covers; adults are 

active from early May through 

August. 

Injury. - Long, narrow patches 

of epidermis about 2 mm wide and 4 

to 10 mm long are eaten from the 

undersides ofleaves (fig. 16b). Heavily damaged leaves turn brown and 

drop prematurely in late summer. 

Prevention and Control.-

Trees should be kept in vigorous 

condition; direct controls are rarely 

needed. 

Spring Cankerworm 

Pest. - Spring cankerworm, Paleacrita vernata (Peck); caterpillars 

are typical loopers; brown to black 

with yellow stripes (fig. 16c); occur 

in the Eastern United States and 

southern Canada; 25 to 48 mm 

long; produce one generation per 

year. 

Injury. - In the spring, young 

larvae eat holes in the leaves; later 

18 

the whole leaf is eaten except for the 

midrib and major veins; defoliation 

stresses the trees. 

Prevention and Control.-

Sticky bands around tree trunks 

will trap the wingless females; 

chemical or biological controls are 

occasionally needed. 

Fall Webworm 

Pest. - Fall webworm, Hyphantria cunea (Drury); mature larvae 

are 25 mm long, pale yellow to 

greenish and with hairy, red or 

black heads; occurs throughout the 

United States and southern Canada; produces one to four generations per year. 

Injury. - Caterpillars make 

webbed nests around leaves at 

branch ends, living and feeding in 

groups inside the nests; populations 

and webbed nests are most abundant in late summer and fall (fig. 

16d). 

Prevention and Control.-

Natural enemies are usually effective; webbed nests can be pruned 

from small trees; chemical or biological controls may be needed. 

Forest Tent Caterpillar 

Pest. - Forest tent caterpillar, 

Malacosoma disstria Hubner; caterpillars have a dorsal row of keyhole-shaped, white spots bordered 

by pale-bluish lines (fig. 16e); 

mature larvae are 50 mm long; 

occurs throughout the United 

States and Canada; produces one 

generation per year. 

Injury. - Caterpillars begin feeding on ash foliage as it emerges in 

early spring; first noticeable signs 

of attack are sparse crowns and falling frass; caterpillars feed for 4 to 6 

weeks. 

Prevention and Control.-

Parasites, predators, and · diseases 
keep most infestations in check; 

chemical and biological controls 

may be needed. 

Ashleaf Gall Mite 

Pest. - Ashleaf gall mite, Aceria 

chrondriphora Keifer; mites are 

elongate, spindle shaped, and soft 

bodied; hardly visible to the naked 

eye; live inside leaf galls throughout 

the United States and southern 

Canada. 

Injury. - The galls on the upper 

surface of leaves are greenish yellow, 2 to 3 mm in diameter (fig. 16f), 

reniform in shape, solitary but 

numerous, scattered along the lateral veins, and reduce esthetic value 

of trees. 

Prevention and Control.-

Natural controls are usually adequate; fallen leaves should be raked 

and destroyed; direct controls are 

rarely needed. 

Figure 16. - (a) Curled leaves from leaf roll midge; (b) leaf beetle 

feeding symptoms; (c) spring cankerworm; (d) fall 

web worm tents in young ash; (e) forest tent caterpillars; (f) leaf galls caused by ashleaf gall mites. 

19 
SEEDLING DISEASES 

Damping-Off, Cylindrocladium spp., Fusarium spp., Phytophthora spp., 

Pythium spp., Rhizoctonia spp. 

Importance. - Damping-off is 

the most important and widespread 

disease of ash seedlings in tree nurseries. The disease is most prevalent in cool, low-lying areas where 

standing water persists, in acidic 

soils, and under any conditions 

where seedling growth is poor. 

Seedling density may be reduced up 

to 25 percent or more when poor 

cultural practices are used. 

Identifying the Disease.-

Damping-off may prevent the emergence of seedlings from the soil as 

the seeds or hypocotyls are 

attacked. Seedlings attacked after 

emergence fall over because the 

hypocotyls are rotted at or below 

the soil line (fig. 17). Both types of 

damping-off result in reduced seedling survival causing nonuniform 

seedling sizes and densities. 

Identifying the Fungi. - Many 

fungi prevalent in soils can cause 

damping-off. Fusarium spp., 

Pythium spp., and Phytophthora 

spp. are most active in cool, wet 

soils, whereas Cylindrocladium 

spp. and Rhizoctonia spp. are more 

common in warm, wet soils. 

Biology. - The soil-borne fungi 

that cause damping-off of seedlings 

are able to survive in the soil in the 

absence of a host. All produce 

resistant spores or sclerotia that 

survive in the soil until root exudates stimulate their germination 

or growth, leading to the infection 

of seeds or seedlings. 

Control. - Damping-off can be 

controlled with cultural practices. 

Seeds should be planted on welldrained sites or in raised beds at 

soil temperatures above 15 °e, 

avoiding dense stands. Nitrogen fertilizers should not be applied until 

seedlings are 6 weeks old. Soil acidity should be maintained at pH 6.0 

or slightly above. Soil fumigation or 

seed treatment with fungicides is 

sometimes necessary for adequate 

control. 

'./~i- \~ , 

20 

I: " . t 

Figure 17. - Ash seedlings with symptoms 

of postemergence damping-of{. 
LEAF DISEASES 

Anthracnose, Gnomoniella fraxini Redlin & Stack 

Importance. - Ash anthracnose 

may be the most common foliar disease of ashes in the United States. 

It is most important in landscape 

and street-side plantings and in 

plantations, and is less important in 

natural forest stands. 

Identifying the Disease.-

Round to irregular blotches, greenish brown at firsl1, but turning 

brown with age, appear along margins and midribs of leaflets (fig. 

18a). Affected leaflets appear 

scorched and may curl and drop 

from the tree. Small cankers and 

dieback may occur on twigs of trees 

severely defoliated for several years. 

Numerous small, round lesions 

with gray centers and purple-brown 

margins (frogeye leaf spots) may 

develop late in the season (fig. 18b). 

Identifying the Fungus.-

Acervuli, colorless initially and 

darkening with age, can be found 

on leaflets shortly after infection. 

Acervuli are also common on previous-year petioles (fig. 18c) and 

twig cankers. Masses of dull-white, 

to pale-pink conidia may be seen 

exuding from mature acervuli. 

Black perithecia develop over winter 

on petioles, leaves, and twigs on the 

ground. 

Biology. - Expanding leaflets 

and shoots are infected in the 

spring by rain-splashed conidia 

from acervuli on dead petioles 

remaining on trees from the previous year. Additional infections 

may augment the disease during 

the growing season. Anthracnose is 

favored by cool, wet, spring weather 

and a lack of air circulation around 

susceptible tissues. 

Control. - Direct control is rarely 

needed. 

Figure 18. - (a) Shoot infected with anthracrwse, some leafiets have already fallen; 

(b) frogeye leaf spots; (c) acervuli on previous-year petioles. 

21 
Ash Rust, Puccinia sparganioides Ellis & Barth 

Importance. - Ash rust attacks 

most ash species growing east of 

the Rocky Mountains. It is most 

severe near coastal areas where its 

alternate hosts, cord and marsh 

grasses (Spartina spp.), are abundant. Severe damage is infrequent 

since trees usually recover, although 

repeated infections have been 

reported to cause dieback and tree 

mortality. 

Identifying the Disease.-

From mid-April to mid-June, the 

upper surfaces of leaves develop 

yellow-orange spots, while chlorotic 

spots develop on petioles and currentyear twigs (fig. 19a). Swelling of diseased tissues leads to distortion and 

necrosis of leaves, bending of 

petioles, and development of galls on 

twigs. Trees with severe infections 

appear scorched, and affected leaves 

. often drop prematurely. 

Identifying the Fungus.-

Clusters of aecia containing orangeyellow aeciospores appear prominently on twigs, petioles, and lower 

surfaces of leaves (fig. 19b). Yellow 

uredinia develop on alternate hosts 

and are replaced in the fall by darkcolored telia. 

Biology. - This fungus has five 

spore stages of which two must 

occur on alternate hosts for infection of ashes. In the spring, teliospores that overwintered on alternate grass hosts produce basidiospores that infect the current-year 

tissuejs of ashes, causing spermogonia and then aecia to develop. 

Aeciospores are blown to and infect 

alternate hosts on which uredinia 

develop in early summer. During 

the summer, urediniospores repeatedly infect cord or marsh grass. 

Uredinia eventually develop into 

brownish-black telia in the fall. 

Control. - To control severe infections in valuable trees, fungicide 

sprays should be used at 2-week 

intervals in the spring starting at 

bud break. 

Figure 19. -(a) Multiple aecial infections on foliage; (b) aecia on twigs and petioles. 

22 
Mycosphaerella Leaf Spots, Mycosphaerella effigurata (Schwein.) 

House,Mycosphaerella fraxinicola (Schwein.) House 

Importance. - Leaf spots cause 

premature defoliation of ash seedlings, and forest and shade trees in 

North America. Mycosphaerella leaf 

spot, heretofore called "Piggotia 

leaf spot," is most common in nurseries. Infection by Mycosphaerella 

fJY1xinicola, previously called "Phyllostica leaf spot," is a problem in 

large trees. 

Identifying the Disease.-

Leaf spots caused by M. effigurata 

appear in June as flecklike, yellow 

spots, 1 to 3 mm in diameter, on 

upper leaf surfaces. Hundreds of 

flecks may occur on a single leaflet 

(fig. 20a, b). By late summer, dark 

asexual stromata give lower leaf 

surfaces a sooty appearance. Seedlings may defoliate prematurely 

near the end of the growing season. 

Initial leaf spots caused by M. fraxinicola are pale-green, irregular 

blotches, 5 to 15 mm in diameter 

(fig. 20c). Spots sometimes coalesce 

and entire leaflets may die. Trees 

may appear scorched due to necrotic 

blotches on foliage. Severe infections 

can result in premature defoliation. 

Identifying the Fungus. - Both 

M. effigurata and M. fraxinicola 

have two asexual fruiting stages. 

Those of M. effigurata develop earlier in the growing season than 

those of M. fraxinicola. Mycosphaerella fraxinicola produces cylindrical, colorless conidia in contrast to 

the two-celled, colorless conidia of 

M. effigurata. Both species produce 

two-celled, colorless ascospores in 

pseudothecia that mature and overwinter in fallen leaves. Ascospores 

of M. effigurata are 1.5 to 2.0 times 

longer than those of M. fraxinicola. 

Biology. - Ascospores dispersed 

by wind from fallen leaves initiate 

primary infections on new leaves in 

the spring. Wet weather increases 

the severity of the disease. 

Control. - There is no practical 

control available for these leaf 

diseases. 

Figure 20.-(a) Mycosphaerella effigurata on white ash seedlings; (b) M. effigurata 

on green ash in nursery; (c) leaf spots caused by M. fraxinicola. 

23 
Powdery Mildews, Phyllactinia guttata (Wallr.:Fr.) Lev and other 

species. 

Importance. - Powdery mildews cause only minor damage to 

ashes in the Eastern United States. 

On shade and ornamental trees and 

seedlings, progression of the disease can reduce vigor, but it 

does not substantially reduce annual 

growth. Damage to forest trees is 

negligible. 

Identifying the Disease.-

Severe infections can cause distortion of tender, late season shoots, as 

well as chlorosis, foliar browning, 

and premature defoliation. 

Identifying the Fungi. - Powdery mildews are easily identified by 

the white or light-colored, powdery 

fungal growth that develops on 

upper or lower leaf surfaces (fig. 

21a, b). Identification of species 

is based on microscopic examination of cleistothecia, conidia, and 

conidiophores. Cleistothecia are 

minute, yellow to black, sexual 

fruiting structures usually found 

late in the season on the lower surface of leaflets. Cleistothecia of P. 

guttata have straight appendages 

with a bulbous base and asci that 

contain two spores. 

Biology. - Powdery mildews are 

most prevalent where cool to warm, 

humid weather persists with little 

rainfall. Primary infection of ashes 

occurs by ascospores released from 

overwintered cleistothecia on fallen 

leaves. Conidia can cause repeated 

infections during the growing 

season. 

Control. - No control is usually 

needed for this disease. 

Figure 21.-(a) Powdery mildew infection on upper leaf surface; (b) infection on 

lower leaf surface. 

24 
DECLINES, DIEBACKS, AND WILTS 

Ash Yellows, Mycoplasmalike organisms (MLO's) 

Importance. - Ash yellows causes 

substantial growth reduction, decline, 

and mortality of white ash in the 

Northeastern United States. Green 

ash appears to be more tolerant of 

ash yellows. Symptoms similar to 

those of ash yellows have been 

reported in Georgia and Louisiana. 

Trees of all ages and sizes in landscape plantings, hedgerows, and forests are susceptible. 

Identifying the Disease (fig. 

22a). - Symptoms vary with host 

susceptibility and disease progression, but in general, initial symptoms are reduced radial (fig. 22b) 

and shoot growth. Sustained infections can cause branch dieback, 

thin chlorotic crowns, epicormic 

sprouting, bark cracks, early fall 

coloration, and premature death. 

These decline symptoms, however, 

can develop from other causes. 

Witches' brooms (fig. 22c) are definitive, although inconsistent, symptoms of ash yellows. 

Identifying the Pathogen.-

Identification is based on finding 

MLO's in stained sections of phloem 

using a microscope. Tentative field 

diagnosis can be made by the presence of witches' brooms. 

Biology. - Ash yellows is caused 

by MLO's that inhabit phloem 

tissue. MLO's are similar in nature 

to bacteria but lack cell walls. While 

infections are systemic, it is unclear 

how MLO's enter ash trees; insect 

vectors are one possibility. Infected 

white ash appears to be more susceptible to other stresses such as 

drought. 

Control. - Merchantable white ash 

with ash yellows dieback should be 

harvested. Infected landscape trees 

without severe dieback may respond 

favorably to fertilization and 

irrigation. 

Figure 22.-(a) Crown thinning, dieback, and epicormic sprouting; (b) growth 

decline (12 annual rings are present between the arrow and the cambium); (c) witches' broom at base of white ash. 

25 
Ash Dieback, Various causal agents 

Importance. - White ash and 

green ash trees in forests, shelterbelts, and landscape plantings of the 

Northeastern and North Central 

United States are affected substantially by this malady. 

Identifying the Disease (fig. 

23a). - Symptoms of abnormal 

growth are similar to those described 

for ash yellows. Epicormic sprouts 

and witches' brooms, indicators of 

MLO infection, have been associated with ash dieback. Stem and 

branch cankers (fig. 23b) caused by 

various fungi often lead to progressive crown dieback. 

Identifying the Causal 

Agents. - Decline of ashes in the 

absence of MLO infection is usually 

due to multiple biotic and abiotic 

agents. Drought may be the primary cause of dieback in many 

areas. A list of other possible causal 

agents includes at least three 

viruses (fig. 23c), two fungal pathogens (Cytospora pruinosa and 

Fusicoccum spp.), freeze damage, 

and air pollutants. 

Biology. - The initial development of ash dieback frequently 

involves drought stress, which may 

be aggravated by freeze damage, or 

the presence of one or more opportunistic fungal pathogens or 

viruses. Stress induced by other 

agents may be worsened by MLO 

infectons in white or green ash. 

Control. - In forests, sites should 

be carefully selected and species 

composition managed to avoid having mature ashes on droughty sites. 

Tree stress may be reduced in landscape plantings by fertilization and 

irrigation during dry weather. 

Figure 23.-(a) Dieback and thinning in white ash; (b) stem canker caused by 

Cytospora pruinosa; (c) rings pots caused by tobacco ringspot virus. 

26 
Verticillium Wilt, Verticillium albo-atrum Reinke and Berthier and Verticillium dahliae Kleb 

Importance. - This disease is 

prevalent in nurseries and landscape plantings of white and green 

ashes in the Northeastern and Midwestern United States. Rarely has 

it been described in forest stands. 

Identifying the Disease (fig. 

24a, b). - Sudden wilting of foliage 

on one or several branches is typically the earliest visible symptom. 

Leaves turn pale green to yellow 

and may appear scorched before 

falling, although green leaves may 

drop before they wilt. Additional 

symptoms include sparse foliage, 

stunted growth, and dieback. 

Infected sapwood often exhibits 

brown streaking, but this symptom 

is not always present. Trees with 

extensive wilt symptoms in much of 

the crowns will usually die before 

the end of the growing season. 

Identifying the Fungus.-

Fungal hyphae and conidia are visible with magnification in the conducting tissue of infected wood. 

Black micro sclerotia or resting 

hyphae (15 to 100 I-Lm in diameter) and the whorled (verticillate) 

arrangement of conidiophore 

branches can be seen in culture. 

Biology. - Verticillium spp. survive periods of cold and drought by 

producing thick-walled microsclerotia, which may be dispersed in diseased plants and plant parts, eventually infesting the soil. Hyphae 

from micro sclerotia penetrate ash 

roots growing next to them in the 

soil. The fungus also invades the 

host through wounds but spreads 

most rapidly when conidia move in 

the sap stream of conductive tissue. 

In this way, multiple infections can 

occur in large trees, eventually 

reducing or stopping vascular flow 

in diseased branches. 

Control. - Depending on their 

availability, plant cultivars that are 

resistant to verticillium wilt should 

be used. 

Figure 24. - (a) Dieback and leaf scorch in upper right crown caused by¥erticillium 

wilt; (b) scorched leaves. 

27 
CANKERS 

Fusicoccum Canker, Fusicoccum spp. 

Importance. - Cankers and dieback caused by Fusicoccum spp. are 

most severe on sites where trees are 

growing poorly. Small branches are 

most affected, although the bole can 

be attacked. Canker development is 

usually arrested on trees with vigorous growth; however, cankers 

may girdle small limbs resulting in 

dieback and wind breakage. 

Identifying the Disease.-

Annual cankers appear pale brown 

when young, but eventually turn 

dark brown with a distinct boundary between the living and dead 

tissues. Old, inactive cankers appear 

sunken and may be surrounded by 

callus. Dead bark may separate 

from the wood and disappear from 

old cankers not covered by advancing callus. Symptoms alone are 

sometimes insufficient to identify 

this disease. 

Identifying the Fungus. - The 

fungus forms white masses of conidia within minute, asexual fruiting 

bodies (pycnidia) embedded in cankers of diseased branches (fig. 25). 

Conidia must be examined microscopically for identification. 

Biology. - The biology of this disease is incompletely known. Numerous conidia, produced and exuded 

from pycnidia in cankers during 

wet periods, are spread by splashing 

rain and mechanical means. They 

germinate and produce hyphae that 

enter wounds on branches resulting 

from insects, frost, or mechanical 

damage. Stressed trees are more 

easily infected and colonized. 

Control. - Cankers can be minimized through wound prevention, 

pruning out and removing limbs 

with cankers from landscape trees 

during winter, and establishing vigorous planting stock on good sites. 

Figure 25. -Fusicoccum canker on ash stems with pycnidia embedded in necrotic 

tissue. 

28 
Nectria Canker, Nectria galligena Bres. in Strass. 

Importance. - Perennial Nectria 

canker is among the most common 

and easily recognized diseases of 

ashes and other hardwood trees in 

the East and South. The disease is 

prevalent in cool, humid climates or 

where isolated pockets of cool air 

collect, especially on poorly drained 

soils. 

Identifying the Disease.-

Cankers begin as small, inconspicuous, dark depressions on 

young stems. The fungus penetrates the cambium and establishes 

a perennial infection. It repeatedly 

kills callus tissue that forms 

annually at the edge of the lesion, 

giving rise to a targetlike, perennial 

canker with concentric rings of 

dead callus (fig. 26). Cankers seldom girdle the bole. 

Identifying the Fungus. - The 

small (1 to 2 mm diameter), brightred to orange perithecia form from 

autumn through spring, near 

young cankers with bark, in bark 

crevices, or at the margins of old 

cankers lacking bark. Occasionally, 

microscopic cream-colored sporodochia form during moist weather. 

Biology. - Ascospores expelled 

from perithecia during rainy periods 

in the spring and autumn are dispersed by wind and water to 

wounds such as frost cracks, sunscald lesions, leaf scars, hail 

wounds, and senescing lower 

branches. The ascospores germinate to produce hyphae that infect 

stems and initiate canker development throughout the groWing season. The fungus overwinters as 

mycelia in cankers and as 

ascospores in perithecia. 

Control. - Nectria canker can 

cause significant damage to individual trees, but the low incidence 

and minimal losses attributed to 

this disease rarely warrant control. 

This disease is easily prevented by 

avoiding bark wounds during cool, 

humid conditions. 

Figure 26. -Perennial target canker caused 

by Nectria galligena. 

29 
DECAYS 

BUTIROTS 

Importance. - Decay of the butt 

log in living trees is the most 

serious cause of cull loss for logging 

because it affects the highest valued 

log and weakens the tree. The incidence of butt rot in green ash is less 

than the 40-percent average for 

other southern hardwoods. The extent of decay in the stem increases 

with wound size and age. 

Identifying the Diseases.-

Hollows, abnormal swellings, butt 

bulge, old basal wounds, or fruiting 

bodies indicate butt rot. Decayed 

wood may be soft or brittle and 

brown to white. The decay column 

may extend vertically for several 

meters (fig. 27). Affected trunks are 

weakened and subject to breakage. 

Identifying the Fungi. - Numerous fungi cause butt rot in ashes. 

The most common are Garwderma 

lucidum (Curtis:Fr.) P. Karst., 

Laetiporus sulphureus (Bull.:Fr.) 

Murrill, Lentinus tigrinus (Bull.:Fr.) 

Fr., Phellinus igniarius (L.:Fr.) 

Quel., Pleurotus ostreatus (Jacq.:Fr.) 

P. Kumm., Postia tephroleuca 

(Fr.:Fr.) Jiilich, Rigidoporus lineatus (Pers.) Ryvarden, and R. 

ulmarius (Sowerby:Fr.) Imazeki in 

Ito. Fruiting bodies form less frequently on ashes in the South than 

in northern regions, usually requiring isolation from the wood for identification. 

Biology. - Exposed wounds are 

sites of entry of decay fungi. Spores 

from fruiting bodies are wind disseminated to wounds where they 

germinate, producing hyphae that 

30 

penetrate the tree. The rate of 

decay varies with the fungus, wound 

size, host vigor, and environmental 

conditions. 

Control. - Wound prevention is 

essential because most infections 

occur through injuries including 

mechanical wounds, fire scars, and 

frost cracks extending into the 

wood. Trees should be harvested 

before pathological rotation age to 

minimize degrade. Severely decayed 

trees should be cut and removed. 

Figure 27.-Butt rot of mature ash arising from wounds in the 

lower bole. 
Varnish Fungus Rot, Ganoderma lucidum (Curtis:Fr.) P. Karst. [Syn. 

Polyporus lucidus (Curtis:Fr.) Fr.] 

Importance. - This pathogen 

causes a serious rot of the lower 

bole and roots of green and white 

ashes throughout North America. 

Ganoderma lucidum can kill even 

the largest trees. 

Identifying the Disease.-

Trees affected by varnish fungus 

rot exhibit yellowing, wilting, or 

undersized leaves and dead branches. 

Affected wood of the lower bole 

becomes soft, spongy, and light colored; in advanced stages of deca~ 

increasing susceptibility to windthrow. 

Identifying the Fungus. - The 

fungus produces annual, reddishbrown basidiocarps, singly or in 

clusters and with or without stalks, 

often near the bases of trees (fig. 

28). The upper surface has a 

smooth, lacquered appearance and 

a distinct, lighter margin that turns 

darker with age. The undersides of 

basidiocarps have a white, porous 

surface when fresh. However, basidiocarps do not necessarily indicate 

extensive decay or imminent death. 

Biology. - Brown spores released 

from basidiocarps are dispersed 

throughout the summer during 

humid periods. Wounds on root 

flares and the lower bole are primary infection courts. Spores germinate and produce mycelia that 

attack the sapwood of all major 

roots and the butt section of the 

bole. Tree vigor may decline as 

decay of the sapwood advances. 

Rates of decay appear to be determined by tree vigor, which is 

often influenced by environmental 

stresses. 

Control. - In urban settings, 

phenoxy-type herbicides applied in 

lawn fertilizers can sometimes predispose trees to varnish fungus rot. 

Cultural practices to reduce drought, 

water stress, and wounding are 

recommended. 

Figure 28. - Basidiocarps of Ganoderma lucidum developing on trunk and roots of 

ash with varnish rot. 

31 
Sulfur Fungus Rot, Laetiporus sulphureus (Bull.:Fr.) Murrill [Syn. Polyporus sulphureus (Bull.:Fr.) Fr.] 

Importance. - The sulfur fungus causes one of the most important rot diseases of ashes and many 

other hardwoods in the Eastern 

and Southern United States. 

Identifying the Disease. - A 

reddish-brown, cubical rot of the 

heartwood may develop in the roots, 

butt, or upper stem of the tree (fig. 

29a). The outward growth of the 

fungus from decaying heartwood 

may kill zones of vascular cambium 

and sapwood to form elongated cankers appearing as depressions in 

the bark. 

Identifying the Fungus. - The 

fungus annually produces brightyellow to orange, shelflike basidiocarps, 20 to 60 cm wide, during 

the summer and autumn on living 

trees in advanced stages of decay 

(fig. 29b). These fruiting bodies 

often develop in overlapping clusters from stem cankers and persist 

throughout the winter in the 

South. Their presence usually 

indicates extensive decay of the 

heartwood. 

Biology. - Fruiting bodies release 

spores during wet, winter months 

in the South. Basidiospores germinate and produce mycelia that 

infect trees through dead branch 

stubs and wounds of trunks or 

occasionally through roots. The 

white to pale-yellow mycelium develops an extensive rot column for 

many years before fruiting bodies 

are produced. 

Control. - Bark wounds in forest 

stands should be avoided, and protuberant dead branch stubs should 

be removed from high-valued trees 

in urban areas to accelerate formation of callus over branch stub 

wounds. 

Figure 29. -(a) Brown cubical rot of heartwood and sapwood in the upper trunk 

caused by the sulfur fungus; (b) basidiocarp of Lae.tiporus sulphureus 

on upper trunk of green ash. 

32 
STEM ROTS 

Perenniporia Stem Rot, Perenniporia fraxinophila (Peck) Ryvarden 

[Syn. Fomes fraxinophilus (Peck) Sacc.] 

Importance. - Perenniporia 

stem rot causes a white, mottled 

heartrot of all major species of 

ashes from Tennessee westward to 

Arizona and northward into Canada. It is a major contributor to the 

decay of green ash stems in the 

shelterbelts of the Great Plains. 

Identifying the Disease.-

Heartwood decayed by this fungus 

is straw yellow to yellowish white, 

soft, and crumbly (fig. 30a). Trees 

in advanced stages of decay are susceptible to breakage and windthrow, especially in the shelterbelts 

of the Great Plains. 

Identifying the Fungus.-

Perennial, bracket-shaped basidiocarps usually form on the bole 

and major branches near branch 

stubs (fig. 30b). Basidiocarps are 

initially dirty white on the upper 

surface, but darken and become 

cracked with age. The lower surface 

is white and porous. They may grow 

to over 25 cm in diameter. 

Biology. - Basidiospores released 

from basidocarps during wet 

periods germinate to produce 

hyphae that infect trees mainly 

through branch stubs and grow 

down the branch trace to the heartwood to initiate decay. Fruiting 

bodies may develop and accumulate 

on the bole for many years as the 

decay column expands. The incidence of basidiocarps on ashes is 

often directly proportional to trunk 

diameter. 

Control. - Infection can be 

reduced by preventing wounds and 

trimming branch stubs to allow 

callus to cover the wounds, particu1arly in older, less vigorous landscape trees. Precautions should be 

taken to protect healthy crop trees 

during thinning and harvesting 

operations in forest stands. 

Figure 30. - (a) Heartwood decay caused by Perenniporia fraxinophila; (b) perennial 

conk under branch stub on living green ash. 

33 
TOP ROTS 

Importance. - Top rots result 

from invasion of limbs by many of 

the same fungi that cause butt rots. 

The incidence of top rot is typically 

lower than that of butt rot. Top rot 

often follows limb damage by ice or 

snow. Decaying limbs and tops may 

break, creating a hazard to people 

and property in urban areas. Losses 

of wood volume are usually insignificant. 

Identifying the Disease.-

Broken or decayed limbs and branch 

scars often indicate top rot. The vertical extent of decay behind young 

or small branch scars is typically 

insignificant, but may extend into 

the bole and exceed 1 m behind old, 

larger branch scars. 

Identifying the Fungi. - Fruiting bodies can be used to identify 

these fungi, but they may not 

always be present. Identification by 

cultural characteristics instead of 

from fruiting bodies has been used 

with limited success because of the 

34 

difficulty in isolating these fungi 

from the wood. 

Biology. - The life cycles of 

decay fungi causing top rots are 

similar to those of fungi causing 

butt rots. However, different pioneer micro-organisms are usually 

associated with the decay process in 

limbs than in trunks. Basidiospores 

are often disseminated from conks 

on hardwood species other than 

ashes. The spores produce hyphae 

that infect branch stubs, wounds, 

and scars, initiating decay. 

Control. - Recognizing top decay 

and early harvesting of infected 

trees are useful means of reducing 

losses. Minimizing logging injuries 

can help reduce top rot in growing 

stock. Management alternatives 

should favor good growth to reduce 

the prospect of infection. Forest 

stands should be managed with 

proper stocking to reduce storm 

damage. 
ROOT DISEASES 

Corticium Root Rot, Scytinostroma galactinum (Fr.) Donk [Syn. Corticium galactinum (Fr.) Burt] 

Importance. - This soil-borne 

pathogen has a wide range of hosts 

and causes a white root rot of ashes 

and many other hardwoods and 

conifers. It has the potential to 

cause extensive damage to trees 

growing on poor sites, but green ash 

is generally less susceptible to this 

disease than many other species. 

Identifying the Disease. - The 

first symptoms usually include loss 

of vigor and thinning of crowns. 

Adventitious sprouts from roots or 

stems and small leaves may appear 

before the tree dies. Trees that die 

typically retain dead leaves until 

the next year. Trees with extensive 

white root rot are susceptible to 

windthrow (fig. 31a). 

Identifying the Fungus. - The 

fungus produces very small, inconspicuous fruiting bodies on affected 

roots and the root collar. Fruiting 

bodies can be observed only with 

magnification. However, a white, mycelial mat, which covers the root collar and roots below the soil line, can 

easily be detected by removing soil 

from the base of the tree (fig. 31b). 

Biology. - The fungus can survive on dead roots and stumps and 

spread to living roots. Insects may 

also disseminate the fungus to 

healthy trees. Spores released from 

fruiting bodies may germinate to 

produce hyphae that invade dead, 

woody tissue. The disease gradually 

kills roots, resulting in decline and 

sometimes death of infected trees. 

Control. - Control measures are 

not economically feasible in natural 

stands. In plantations or urban settings, diseased trees and affected 

roots should be removed to reduce 

the spread of the disease to adjacent 

trees. The triazole systemic fungicides show promise for reducing 

spread in high-valued trees. 

Figure 31. - (a) Corticium root rot of small green ash tree; (b) white mycelial mat on 

roots. 

35 
Texas Root Rot, Phymatotrichopsis omnivora (Duggar) Hennebert [Syn. 

Phymatotrichum omnivorum (Shear) Duggar] 

Importance. - The Texas root 

rot pathogen has a wide range of 

broad-leaved hosts throughout certain areas of the Southwestern 

United States. Ashes planted in old 

fields or residential areas may be 

affected by this disease. 

Identifying the Disease. - The 

disease is characterized by sudden 

wilting and death of infected seedlings (fig. 32). Older trees may 

exhibit reduced growth and vigor. 

Coalescing, necrotic lesions on roots 

may appear down to a soil depth of 

30 cm. The inner bark and cambium turn brown or black and 

mushy, and the root collar may be 

girdled. As the roots die, leaves of 

affected trees turn yellow or bronze 

before they wilt. Dieback and thin 

crowns are common. 

Identifying the Fungus.-

Spore mats develop on the soil surface during warm, wet periods. 

Infected roots are covered by yellowish, fluffy mycelia that penetrate 

the bark. Mycelial strands, with distinct, cross-shaped hyphae, are the 

best diagnostic microscopic feature. 

Black sclerotia formed from compact hyphae on dying roots may be 

found in the soil. 

Biology. - The fungus persists 

in the soil for many years as sclerotia, which germinate to produce 

infectious hyphae that enter roots 

through natural openings and 

wounds. The hyphae colonize the 

root and grow up to 9 cm per year 

along infected roots and in the soil. 

The fungus is favored by warm, cal-' 

careous soils with high clay content 

and a pH of 7.2 to 8.5. 

Control. - Soil amendments to 

increase soil acidity in alkaline soils 

inhibit growth of the fungus. Ammonium sulfate or ammonium phosphate fertilizer should be applied 

at 4.5 kg per 9.3 m2 • The soil should 

then be soaked to 30 to 60 cm. 

Planting trees in infected areas or 

on land previously planted in cotton 

should be avoided. 

Figure 32. - Texas root rot of ash seedlings in a commercial nursery. 

36 
Mushroom Root Rot, Armillaria tabescens (Scop.) Dennis, Orton & 

Hora [Syn. Clitocybe tabescens (Scop.) Bres.] 

Importance. - Mushroom root 

rot causes losses in more than 200 

plant species in the Southern United 

States from Oklahoma eastward. 

Ash trees are more commonly 

attacked when growing slowly and 

already weakened by wounding or 

defoliation. 

Identifying the Disease.-

Leaves turn yellow, become sparse 

or are undersized, and drop prematurely. Roots may be partially 

decayed or completely girdled at the 

root collar. Basal lesions may extend 

up to 30 cm or more above the soil 

line. Affected trees show general 

loss of vigor and dieback and have 

increased susceptibility to windthrow. 

Identifying the Fungus. - Clusters of yellow mushrooms develop 

at the base of infected trees from 

June through October, usually 

associated with summer rain and 

moist soil (fig. 33a, b). Mushrooms 

produce white basidiospores. The 

root collar must be excavated for 

diagnosis if mushrooms are not present. White to tan mycelial mats 

form under the bark (fig. 33c). Narrow, black mycelial strands (rhizomorphs) occasionally develop in 

bark fissures or under dead bark 

above mycelial mats on the root 

surface. 

Biology. - The fungus can persist in dead or dying root tissues for 

many years. The rhizomorphs spread 

through the soil, attach to roots, 

and produce hyphae that penetrate 

healthy tree roots. Infected roots 

gradually die, resulting in decline 

and mortality of the tree. Mushrooms may be produced when large 

roots or the stem dies. 

Control. - Cultural practices 

that reduce tree stress should be 

used. Mortality can be minimized 

by regular fertilization and irrigation. Infected trees and roots should 

be removed from the soil before 

replanting. 

Figure 33. - (a) Mushroom root rot in the lower trunk of mature green ash; 

(b) closeup of basidiocarps arising from roots in the soil; (c) root and 

bole rot showing white mycelium under the bark of decayt!d wood. 

37 
PARASITIC PLANTS 

Mistletoe, Phoradendron spp. 

Importance. - Extensive infections and mortality are uncommon 

in ashes. However, infections occur 

typically in open -grown trees. This 

true mistletoe is used as greenery 

in Christmas decorations. 

Identifying the Injury.-

Affected branches may be galled or 

swollen at the site of infection, and 

multiple infections may result in 

loss of growth. Branches beyond the 

mistletoe may be stunted or die 

back. 

Identifying the Parasite (fig. 

34a, b). - The mistletoe plant has 

stout, green stems and dark-green, 

leathery leaves. It is seen best in 

winter growing on major and minor 

branches and twigs of the host. The 

plant has opposite branching and 

inconspicuous flowers and produces 

white berries in the fall. 

Biology. - This perennial, evergreen plant grows as a parasite on 

tree branches. The seeds are covered with a sticky, gelatinous coating and are spread by birds and 

small mammals. The seeds lodge on 

young branches and germinate. A 

rootlike, penetrating structure 

grows into the young branch and 

produces a mistletoe plant. One 

species, Phoradendron serotinum, 

affects many other broad-leaved 

trees in the South and East, but is. 

limited by temperature in its northern range (Kansas to New Jersey). 

Several other species of Phoradendron occur in the West. 

Control. - Control normally is 

not needed in ashes, but pruning 

affected branches at least 30 cm 

below the point of infection may 

provide some control. 

Figure 34.-(a) Multiple infections by mistletoe in mature crowns; (b) mistletoe on 

main stem. 

38 
AIR POLLUTION AND CHEMICAL INJURIES 

Air Pollution Injury (fig. 35a) 

Ashes vary in sensitivity to air 

pollutants, but in general, are intermediate in sensitivity to sulfur 

dioxide and hydrogen fluoride emitted during various types of manufacturing processes. Sulfur dioxide kills the leaf tissue between 

veins, whereas hydrogen fluoride 

kills the leaf margins. White ash is 

sensitive to ozone, which causes 

purple stippling on upper surfaces 

of older foliage. Extremely sensitive 

cultivars may experience growth 

loss. The main precursors of ozone 

originate from automobile exhaust. 

Chemical Injury (fig. 35b, c) 

Ash trees are sensitive to many 

chemicals, but the most frequent 

damage is caused by herbicides. 

Symptoms are highly variable and 

include leaf curl, chlorosis, partial 

leaf necrosis, and premature leaf 

fall. Affected branches or the entire 

crown may drop its leaves and 

refoliate repeatedly during a single 

growing season. Young trees may be 

killed by acute exposures. Symptoms of air pollution or chemical 

injury may be difficult to distinguish from symptoms induced by 

other abiotic agents or infections 

caused by biotic agents. 

Figure 35. - (a) Purple stippling caused by ozone; (b) leaflet curling and scorching 

caused by an herbicide; (c) marginal necrosis caused by ammonia. 

39 

PESTICIDES 

Registered chemicals for control of insects that attack ashes. (See 

labels for dosages, application methods, and restrictions.) 

Insect Insecticide Insect Insecticide 

Ash sawflies Acephate Scale insects Carbaryl 

Carbaryl Chlorpyrifos 

Chlorpyrifos Diazinon 

Diazinon Methoxychlor 

Malathion 

Planthoppers Carbaryl 

Sphinxes Acephate Diazinon 

Carbaryl 

Chlorpyrifos Ash bark Chlorpyrifos 

Diazinon beetles Lindane 

Ash plant Acephate Mites Acephate 

bugs Chlorpyrifos Carbaryl 

Diazinon Diazinon 

Dicofol 

Woolly ash Acephate 

aphid Carbaryl Seed weevils Acephate 

Chlorpyrifos Carbaryl 

Diazinon Diazinon 

Malathion 

Leafroll Carbaryl 

Borers Chlorpyrifos midges Diazinon 

Lindane 

Spring Bacillus 

cankerworm thuringiensis 

Fall webworm Chlorpyrifos 

Forest tent Diazinon 

caterpillar 

41 
PESTICIDES 

Registered chemicals for control of diseases that attack ashes. (See 

labels for dosages, application methods, and restrictions.) 

Disease Fungicide Disease Fungicide 

Damping-off Captan (seed Leaf spots Benomyl 

treatment) Captan 

Chloroneb Dodine 

Dazomet Ferbam 

Etridiazol 

Methyl bromide Powdery Benomyl 

+ chloropicrin mildews Chlorothalonil 

(Preplanting Lime sulfur 

soil 

fumigation) Ash dieback Treat for causal 

agent 

Anthracnose Benomyl 

Metallic copper Root rots Captan 

Zineb Etridiazol 

Ash rust Captan 

Ferbam 

42 
MAINTAINING TREE HEALTH 

Trees should be managed to optimize vigor because healthy trees are 

less susceptible to attack and injury 

by insects and diseases. The following cultural practices, singly or in 

combination, can be used to promote and maintain good tree health 

in forest stands, plantations, nurseries, shelterbelts, and ornamental 

plantings: 

1. Match ash species and seed 

source with their adapted 

sites. 

2. Use vigorous planting stock, 

and select pest-resistant cultivars when available. 

3. Ensure that trees receive sufficient water, nutrients, and 

sunlight through irrigation, 

fertilization, and proper 

spacing. 

4. Maintain proper stocking in 

forest stands. 

5. Use sanitation practices such 

as pruning out and removing 

dead and symptomatic limbs 

and branches, and raking 

and removing insect-infested 

and diseased leaves; this 

reduces levels of hibernatinginsects and overwintering 

inoculum reservoirs that initiate new infections the following year. 

6. Prevent or minimize injuries 

and wounding from harvesting, fire, or other sources 

that can ~reate easy entry 

points for ash pests. 

7. Utilize cultural practices 

that favor natural controls 

such as birds and other predators, parasites, and insect 

pathogens. 

8. Exercise caution in the use of 

broadleaf herbicides on lawns 

around ornamentals and 

shade trees because these 

herbicides have the potential 

to damage ash trees. 

9. Be aware of early insect feeding or disease symptoms; 

this will allow for the greatest number of options in 

managing a pest problem. 

10. Use pesticides only when and 

where they are absolutely 

needed and avoid using more 

than the recommended rates 

to prevent development of 

pest resistance. 

43 
GLOSSARY 

Acervulus( -i) - a saucer-shaped, 

fungal structure embedded in 

host tissue in which conidia 

form. 

Aeciospore - a type of spore 

formed in an aecium of a rust 

fungus. 

Aecium( -ia) - a cuplike, fruiting 

body produced by rust fungi. 

Ascocarp - the sexual, fruiting 

body of Ascomycetes. 

Ascospore - the sexual spore of 

Ascomycetes. 

Basidiocarp - the sexual, fruiting 

body of Basidiomycetes. 

Basidiospore - the sexual spore of 

Basidiomycetes. 

Bole - the main stem or trunk of a 

tree. 

Butt - the lower bole of the main 

stem. 

Callus - a protective tissue that 

forms to cover wounds on stems 

and branches. 

Cambium - a thin layer of cells 

between the phloem and xylem. 

Canker - a definite, localized, necrotic lesion of the bark and 

cambium. 

Conidium(-ia)-an asexual, fungal spore. 

Conidiophore - a fungal structure bearing asexual spores. 

Conk - a basidiocarp of wood decay 

fungi. 

Crochet - a tiny hook on the prolegs of caterpillars. 

Damping-off - a necrotic disease 

of seedlings that causes rotting 

of the hypocotyl and prevents 

emergence of the new shoot or 

causes the new shoot to fall over. 

Dieback - the gradual dying of a 

tree crown usually from the top 

down and from the outside in. 

44 

Elytra - the hard forewings (wing 

covers) of beetles. 

Frass - wood fragments mixed 

with borer excrement. 

Gallery - a long passage chewed in 

the bark, cambium, or wood. 

Hypha( -e) - a single filament of a 

fungus mycelium. 

Infection court - the point where 

a pathogen enters its host. 

Inoculum( -a) - the spore, mycelium, or other propagule of a 

pathogen that initially infects a 

host. 

Maggot - a legless larva of various 

flies. 

Mycelium( -ia) - a collection of 

hyphae that make up a fungus 

body. 

Necrotic - composed of dead cells. 

Pathological rotation - the harvesting of trees before the. age at 

which the rate of wood volume 

loss due to decay fungi exceeds 

the annual production of new 

wood. 

Perennial canker - a canker that 

expands indefinitely. 

Perithecium( -ia) - a flask-shaped 

ascocarp in which ascospores are 

formed. 

Phloem - the food-conducting vascular tissue under the bark of 

trees. 

Pronotum - the upper surface of 

the prothorax. 

Pseudothecium( -ia) - the flaskshaped ascocarp similar to a perithecium but without a definite 

fungal wall. 

Rhizomorph - a compact mass of 

vegetative hyphae that have 

fused together to form a thick, 

usually dark, rootlike strand. 

Sapwood - the outer, water-conducting wood (xylem) of the tree 

stem. 
Sclerotium( -ia) - a firm, often 

rounded, compact mass of fungal 

hyphae that form a resistant survival structure. 

Spermatium( -ia) - a nonmotile, 

uninucleate spore (gamete) required for sexual reproduction in 

some fungi. 

Spermogonium( -ia) - a fungal 

structure in which spermatia 

are produced. 

Sporodochium( -ia) - a cushionshaped stroma covered with 

conidiophores. 

Stroma( -mata) - a mass or mat of 

hyphae in or on which fruiting 

bodies form. 

Teliospore - the spore of a rust 

fungus from which basidia and 

basidiospores form. 

Telium( -ia) - a fruiting structure 

producing teliospores of rust 

fungi. 

Urediniospore - the spore of a 

rust fungus, formed in a 

uredinium, that can repeatedly 

infect its host. 

Uredinium( -ia) - a fruiting structure of a rust fungus that gives 

rise to urediniospores. 

Witches' broom - an abnormal 

growth of branches forming a 

broomlike cluster. 

The policy of the United States Department of Agriculture 

Forest Service prohibits discrimination on the basis of race, 

color, national origin, age, religion, sex, disability, familial 

status, or political affiliation. Persons believing they have 

been discriminated against in any Forest Service related 

activity should write to: Chief, Forest Service, USDA, P.D. 

Box 96090, Washington, bc 20090-6090. 

The use of trade, firm, or corporation names in this paper 

is for the information and convenience of the reader. Such use 

does not constitute official endorsement or approval by the 

U.S. Department of Agriculture of any product or service to 

the exclusion of others that may be available. 

45 
Solomon, J.D.; Leininger, T.D.; Wilson, A.D.; Anderson, 

R.L.; Thompson, L.C.; McCracken, F.I. 1993. Ash pests: 

A guide to major insects, diseases, air pollution injury 

and chemical injury. Gen. Tech. Rep. SO-96. New 

Orleans, LA: U.S. Department of Agriculture, Forest 

'Service, Southern Forest Experiment Station. 45 p. 

This booklet will help nurserymen, resource managers, 

pest control personnel, and homeowners to prevent, 

identify, and control ash pests. 

Keywords: Biology, borers, control, defoliators, Fraxinus, 

fungi, identification. 
CAUTION 

Pesticides used improperly can be injurious to humans, 

animals, and plants. Follow the directions and heed all 

precautions on the labels. 

Store pesticides in original containers under lock and 

key-out of the reach of children and animals-and away 

from food and feed. 

Apply pesticides so that they do not endanger humans, 

livestock, crops, beneficial insects, fish, and wildlife. Do 

not apply pesticides when there is danger of drift, when 

honey bees or other pollinating insects are visiting plants, 

or in ways that may contaminate water or leave illegal 

residues. 

Avoid prolonged inhalation of pesticide sprays or 

dusts; wear protective clothing and equipment if specified 

on the container. 

If your hands become contaminated with a pesticide, 

do not eat or drink until you have washed. In case a 

pesticide is swallowed or gets in the eyes, follow the firstaid treatment given on the label, and get prompt medical 

attention. If a pesticide is spilled on your skin or clothing, 

remove clothing immediately and wash skin thoroughly. 

Do not clean spray equipment or dump excess spray 

materials near ponds, streams, or wells. Because it is difficult to remove all traces of herbicides from equipment, do 

not use the same equipment for insecticides or fungicides 

that you use for herbicides. 

Dispose of empty pesticide containers promptly. Have 

them buried in an approved sanitary land-fill dump. 

NOTE: Some States have restrictions on the use of 

certain pesticides. Check your State and local regulations. 

Also, because registrations of pesticides are under constant review by the Federal Environmental Protection 

Agency, consult your county agricultural agent or State 

extension specialist to be sure the intended use is still 

registered. 
United States 

Department of Agriculture 

Forest Service 

Southern Forest 

Experiment Station 

701 Loyola Ave., Rm .T-10210 

New Orleans, LA 70113-1931 

OFFICIAL BUSINESS 

Penalty for Private Use $300