United States

Department of

Agriculture

Forest Service

Southern Forest

Experiment Station

Research - --

-sozis

May 1991

I Cold-Induced Cankers and Associated Fungi

in a Sycamore Seed Orchard

El. McCracken and R. Rousseau

SUMMARY

Of the trees in a 6-year-old sycamore seed orchard in

Carlisle County, KY, 66 percent developed obscure vertical cankers in the spring of 1990. A variety of woundinvading saprophytes, including Hyalodendron sp.,

Stachylidium sp., Botrytis sp., Phialophora sp., Tn’choderma sp., and Fusarium sp., were isolated from canker

wood. Weather records indicated that trees were subjected to abnormally low temperatures from December

15-25, 1989. Five clones demonstrated an apparent tolerance to the cold damage, but there was no correlation

between clone response and geographic origin of the

clones. The consistent southern orientation of cankers,

record low temperatures in 1989, and apparent absence

of virulent pathogens strongly suggest that the cankers

resulted from freeze damage.

Keywords: P/&anus occidentalis, wound-invading fungi.

INTRODUCTION

Sycamore, Platanus occidentalis L., is a fast-growing,

easily propagated hardwood species that can be grown

on plantations to help meet fiber and fuel needs (Briscoe

1969). However, the plantation ecosystem composed of

genetically similar trees enhances the probability of

damage by pest agents. Tolerance to pests and seed

quality may vary greatly between seed sources

(Coggeshall and others 1981). Seed orchards derived

from desirable selections can supply uniform high-quality seed for annual production needs, but can be affected

by canker fungi, cold temperatures, or other agents (Filer

and others 1977). The purpose of this study was to

determine the cause(s) of extensive canker-like bark

necrosis in a 6-year-old sycamore orchard near

Wickliffe, KY, established from progeny-tested selections of 25 individuals from North Carolina, Illinois, Kentucky, Alabama, Tennessee, and Mississippi.

MATERIALS AND METHODS

A 3-acre sycamore seed orchard with 324 trees was

established in Carlisle County, KY in 1985 from progeny

test selections grafted onto l-year-old local root stock.

The orchard was cultivated through the first two growing

seasons and mowed periodically. Most trees produced

seed by the third year. Several trees died (23 percent)

due to graft failure. Trees were rated annually in the

spring for anthracnose, canker disease, and seed viability after the third growing season.

In the spring of 1990, many of the trees developed flat,

obscure vertical necrotic streaks on the stem,s that

appeared as 1- to 2-year-old Ceratocystis firnbriata Eli.

and Halst. F. platani Walker infections. All trees in the

seed orchard were examined for extent and location of

injury symptoms during July 1990. Sections were

removed from stems at 2-, 3-, and 5-meter intervals

through the canker. The wood samples were split, and

chips approximately 1 mm3 were removed aseptically

without surface treatments from the transmission zone

between necrotic tissue and live stem wood. Fungal isolates were recovered from samples on potato dextrose

agar after incubation without light at 68 “F. Fungi were

identified after 1 to 2 weeks of incubation.

Weather records of recent past winters from a nearby

location (Mayfield, KY) were obtained from the Midwest

Southern Forest Experiment Station/l-10210 U.S. Postal Services Bldg., 701 Loyola Avenue, New Orleans, La. 70113

Forest Service, U.S. Department of Agriculture.

Serving Alabama, Arkansas, Louisiana, Mississippi, E. Oklahoma, Tennessee, E. Texas, Puerto Rico, U.S. Virgin Islands

1
Agricultural Weather Service Center, National Oceanic

and Atmospheric Administration, Purdue University, and

evaluated for periods of possible temperature damage.

RESULTS AND CONCLUSIONS

Fungi were recovered from 32 percent of more than

200 tissue samples examined; 30 percent yielded no

microorganisms, and 38 percent yielded bacteria only.

The necrotic tissues had been invaded by the wood saprophytes Hyalodendron sp. (8 percent), unidentified spp.

(8 percent), Stachylidium sp. (7 percent), Botrytis sp. (5

percent), Trichoderma sp., (2 percent), and Fusarium sp.

(2 percent). No isolates of the fungi C. fimbriata platani,

-20 I . .^ I. ..-..- _.__ .._ -.--~--.. . . .._ ._~ ._ _~ __.- __-__

11/l 11111 11/21 12/l w/11 1.2/2112/31 l/10 l/20 1130 219 z/19

oi

-20 .~_~~~. ~_.. . ~ . . __ -.-__-. .~ ..--.-J

11/l 11111 11/21 12/l 12/1112/2112/31 1110 l/20 l/30 z/9 2119 2129

Phomopsis sp., Botryodiplodia theobromae Pat., or

other pathogens capable of producing elongate cankers

were recovered.

The damage data from the 25 clones showed that 145

of the 220 total ramets (66 percent) exhibited typical

symptoms of vertical necrotic streaks. The majority of

the clones (16) had both affected and unaffected

ramets. Very few clones showed complete resistance or

susceptibility. Four clones showed no damage, while five

clones were completely affected. There was no apparent

correlation between damage and geographic origin of

the clones. Weather records from Mayfield, KY, show a

record cold period from December 15 to December 25,

1989 (fig. 1). Such low temperatures were not recorded

during the previous three winters, and there was no evi-

- 20 I-- ____-i1111 11111 11/21 12/l 12i1112/2112/31 l/10 l/20 l/30 z/9 z/19

Figure 1 .--Da//y maximum and minimum temperatures (‘F) at Mayfield, KY; (A) during the unusually cold winter of 1989- 1990. compared with previous winters of (ES) 1988- 1989, (C ) 1987-l 988, and (0) 1986- 1987.

Francis I. McCracken I S prtncipal plant pathologist, U.S. Department of Agriculture, Forest Service, Southern Forest Experiment Station, Stoneville,

MS 38776. R. Rousseau is forest research geneticist at Westvaco. Wickliffe, KY 42087.

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dence of damage during those years. Similar low temperatures were recorded during December of 1983.

The presence of only known saprophytic fungi in

necrotic zones, consistent southeast to southwest orientation of necrosis, and the record low temperatures during December 1989 strongly suggest that the vertical

necrotic streaks resulted from freeze damage.

Failure to isolate the known canker-producing fungus,

C. fimbriata platani, alone cannot be considered conclusive evidence that the damage was due to other causes.

However, by August 1990, the vertical necrotic zones

were developing callouses which is not typical of sycamore canker stain. The few trees that demonstrated thin

crowns and wilt symptoms typical of canker stain were

found to exhibit graft incompatibility that resulted in

restricted root stock growth at the graft line. This abnormality in the vascular system could account for the wilt

symptoms exhibited during periods of summer water

stress.

The arctic air mass responsible for the abnormally low

temperatures in December 1989 also damaged several

cold-susceptible or woody species across the South.

During the years recorded, previous low winter temperature extremes occurred only in 1983. The wounds on

affected trees in the seed orchard do not represent a significant threat by infection of the principle canker-producing fungi because old exposed wounds do not readily

support establishment of C. fimbriataplatani (McCracken

1987). Wounds are first inhabited by saprophytic fungi

such as those isolated and may be invaded by wood

decay fungi, which would further weaken the stems

(McCracken 1988). However, the scar widths were small

enough to close in 1 to 3 years and arrest decay development. Early season cold extremes cause considerable

injury because of water content in tissue. Stem surface

temperatures may change greatly (>lOO “F) in a few

hours on the south side during abnormally cold, clear

weather. Such extreme temperature variations also

cause extensive tissue damage even during the dormant

season (Boyce 1948). Wound dressings are not advised

for small cold-weather wounds because they are not

highly susceptible to pathogens as are wounds during the

growing season.

Foresters should avoid establishing plantations on

sites with topographic characteristics subject to frost

development. Cultural treatments that promote tree

growth and facilitate wound closure are recommended.

LITERATURE CITED

Boyce, John Shaw. 1948. Forest pathology. 2d ed. New

York. McGraw-Hill. 550 p.

Briscoe, CF. 1969. Establishment and early care of sycamore plantations. Res. Pap. SO-50. U.S. Department of Agriculture, Forest Service, Southern Forest

Experiment Station, New Orleans, LA. 18 p.

Coggeshall, M.V.; Land, SF, Jr.; Ammons, V.C. [and

others]. 1981. Genetic variation in resistance to canker

disease of young American sycamore. Plant Disease.

65: 140-142.

Filer, T.H., Jr.; Solomon, J.D.; McCracken, FI. [and

others]. 1977. Sycamore pests-a guide to major

insects, diseases, and air pollution. [Unnumbered publication]. U.S. Department of Agriculture, Forest Service, Southeast Area, State and Private Forests,

Atlanta, GA, and Southern Forest Experiment Station,

New Orleans, LA. 36 p.

McCracken, FI. 1987. Sycamore canker stain-protection

and eradication [Abstract]. In: Mississippi Academy of

Science. Suppl. 32. Mississippi Academy of Science.

p. 7.

McCracken, FI. 1988. Microorganisms associated.with

canker rots and heart rot of oak. European Journal of

Forest Pathology. 18: 391-396.

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*U.S. GOVERNMENT PRINTING OFFICE: 1991-566-016/20018 3