The

5,i^frCfv^cí^S (^ <'^<^iUav 3 3,

i-e.^ Ax^-, ^^l ¿OVL

in the UNITED STATES

AGRICULTURE HANDBOOK NO. 236

Agricultural Research Service

UNITED STATES DEPARTMENT OF AGRICULTURE
CONTENTS

Page

How to recognize the Japanese beetle J

The adult J

The egg ^

The grub J

The pupa . ^

Present distribution of the beetle in North Amenca 5

Probable ultimate distribution of the beetle in North America 6

Temperature and moisture requirements of the beetle 6

Western spread of the beetle 7

Southern spread of the beetle 8

Northern spread of the beetle 8

How the beetle spreads 8

Seasonal history and habits »

Feeding by adult beetle 12

Type of feeding 12

Factors influencing feeding 12

Toxic plants 1*

Small fruits 14

Tree fruits 15

Truck and garden crops 15

Field crops 17

Ornamental herbaceous garden plants 19

Ornamental shrubs and vines 19

Shade trees 20

Noneconomic plants 21

Feeding by grubs 22

Natural enemies of the beetle 24

Native enemies 24

Imported parasitic insects 24

Entomogenous diseases 26

Fungi 26

Protozoans 26

Nematodes 26

Rickettsias 27

Bacteria 3T

Status of the beetle in 1962 ^ 29

GroHth Thnaih Afrloihiril Piainu

This handbook supersedes Circular No. 332, General Information on the Japanese

Beetle in the United States

Washington, D.C. Issued Deceniber 1962
The

in the UNITED STATES

By WALTER E. FLEMING, Japanese Beetle and European Chafer Investigations,

Entomology Research Division, Agricultural Research Service

The Japanese beetle Pcpillia Japónica Newm., one of our plant pests

of foreign origin, was first found in the United States in 1916 in a

nursery near Riverton, N.J. It was previously known to occur only in

the main islands of Japan. Apparently it had come to this country

with plants before restrictions on the importation of plants and plant

products had been established by tlie Plant Pest Act of 1912.

The beetle is not a serious agricultural pest in Japan, where there

are no large areas favorable for its reproduction and development, or

the abundant supply of food it found m the eastern part of the United

States, and its natural enemies are adecjuate to keep the beetle populations at a low level. In New Jersey it found a generally favorable

climate, large areas of permanent turf for the development of the

.immature stages, almost 300 species of plants to satisfy its voracious

appetite, and no important natural enemies.

Only about a dozen beetles were found in 1916. From this small

beginning the beetle multiplied rapidly and spread xmtil by 1962 it had

invaded over 100,000 square miles in the eastern part of the United

States, and it had become established in several isolated areas beyond

this region of natural distribution. Soon after its establishment in this

country the beetle demonstrated that it was a pest of major

importance.

As the range of the beetle widens each year new groups of people

will meet the invader for the first time. This handbook was prepared

to acquaint such persons with the appearance, life history, habits, and

economic importance of the insect, and with its native and imported

natural enemies. The publication supersedes Circular No. 332, "General Information on the Japanese Beetle in the United States," which

is now out of print. It does not tell in specific detail how to combat the beetle. Recommendations on the use of insecticides to protect

plants from attack by the adult beetle and to destroy grubs in the soil

are modified periodically as more effective materials are developed.

The most recent information on measures for controlling the insect is

given in Farmers' Bulletin No. 2151, "The Japanese Beetle—How To

Control It."

HOW TO RECOGNIZE THE JAPANESE BEETLE

The Adult

The adult beetle (fig. 1) is a beautiful, broadly oval insect nearly

one-half inch long and about one-fourth inch wide. The body is a

bright metallic green ; the legs, a darker green. The hard wing covers

are a coppery brown and extend almost to the tip of the abdomen.

There are two small tufts of white hairs just behind the wing covers

and five patches along each side, which distinguish the Japanese beetle
FiGxmE 1.—The adult Japanese beetle. Five times natural size.

from all other beetles that resemble it. The under surface of the

body is clothed with short grayish hairs.

Both sexes have the same coloring and markings, but the males are

usually slightly smaller than the females. The sexes can be distinguished by the structure of the first pair of legs. As shown in figure

2, the tibial spur of the male terminates in a sharp point, but on the

female this spur is longer and obtusely rounded.

The Egg

The egg of the beetle is elliptical in shape, and approximately onesixteenth inch in diameter. It varies in color from a translucent to

creamy white. The surface appears finely punctate under high magnification, the tiny punctures somewhat hexagonal in shape. After being

in the ground for about a week, the egg begins to swell and eventually

becomes about double its original size. At that time it is more spherical in shape and the developing embryo can be seen through the shell

(fig. 3).

The Grub

A completely white grub, about one-sixteenth inch long, emerges

from the egg. Its head is equipped with biting mouthparts, each of

the three thoracic segments bears a pair of legs, and there are ten
*ifoäo»tef>Ma;»«iw

FiouKE 2.—Fore tibiae and tarsi of the Japanese beetle, greatly enlarged, showing the difference in structure between male and female beetles.

abdominal segments. The last two rows of spines on the underside

of the last abdominal segment, or the anal plate, are arranged in the

shape of a V (fig. 4), a characteristic that distinguishes this grub from

all others. After a few hours, the color of the head changes to a yellowish brown. The grub is usually found in a cell in the soil, curled

in the general shape of a crescent.

As the grub feeds on organic matter and fibrous roots, the accumulation of fecal matter in the hind gut gives the abdominal area a grayish to black appearance. The grub continues to feed and grow until

it is about one-fourth inch long; then it is quiescent for about a day

while it sheds its old skin. The second instar continues to grow until

it is about one-half inch long ; then it molts. By the time the grub

is fully grown, it is about 1 inch long (fig. 5). When mature, the grub

ceases to feed, and ejects any accumulated excrement. The body

gradually becomes pale and shrunken in appearance. This is a semiactive condition between the active grub and the quiescent pupal stage.

The Pupa

The grub transforms to a pupa within the old skin. The pupa

(fig. 6) resembles somewhat the adult beetle, except that the legs,

antennae, and wings are closely folded to the body. It is about one-
J-722

FiQUBE 3.—Mature eggs of the beetle. Eight times natural size.

half inch long and one-fourth inch wide. The body, which at first

is a pale cream color, gradually becomes a pronounced tan and finally

the metallic green of the adult. When the transformation is completed, tlie adult beetle splits tlie enclosing skin and issues forth. It

IS soft and delicate at first, and usually remains in the earthen cell

formed by the grub for several days before emerging from the ground.

J-3079

FiGTJKE 4.—Arrangement of hairs and spines on the underside of the last body

segment of Japanese beetle grubs. The V-shaped arrangement of the last two

rows of spines distinguishes this grub from all others.

4
J-5128

FiouBE 5.—Full-grown Jax>aiiese beetle grub. Six times natural size.

PRESENT DISTRIBUTION OF THE BEETLE

IN NORTH AMERICA

During the five years following the discovery of a few beetles in

1916, the population increased rapidly and spread over an area of

about 270 square miles in southern New Jersey and eastern Pennsylvania. This area increased to 3,200 square miles in 1926, to 6,200

square miles in 1931, to 12,500 square miles in 1936, to 20,000 square

miles in 1941, to 37,500 square miles in 1946, to 60,600 square

miles in 1951, to 94,000 square miles in 1956, and to over 100,000

square miles in 1962, when it extended from southern New Hampshire and Vermont into North Carolina and westward into Ohio and

West Virginia, covering all or parts of 14 States and the District

of Columbia. Local colonies of beetles have developed westward in

Indiana, Illinois, Tennessee, Kentucky, Michigan, Iowa, Missouri,

and California ; southward in South Carolina, Georgia, and Florida ;

and northward in Maine, and in the Canadian Provinces of Ontario

and Nova Scotia. Some of these colonies apparently have been

eliminated by the application of insecticides to the soil, and insecticidal sprays to foliage, and other suppressive measures.

In the infested region along the Atlantic Seaboard the annual range

of temperature is similar to that in the original home of the beetle m

Japan. Precipitation is normally plentiful and uniformly distributed

throughout the year. In some years the region is subjected to pro-
B

FiGUBE 6.- -Pupae of the Japanese beetle. Six times natural size,

view ; B, ventral vlevr.

J-S129

A, Dorsal

longed droughts during the summer, with more or less detrimental

effect on the beetle populations, but it is questionable if the drought

lias been sufliciently severe in any part of the region to eliminate the

insect. During dry summers the beetle selects low-lying, poorly

drained tracts and irrigated land in which to deposit its eggs. When

a dry summer is followed by one with adequate moisture, there is almost invariably an increase in the beetle population. The apparent

permanent establishment of the beetle at many points throughout this

region shows that, in general, the environmental conditions are suitable

for its development.

PROBABLE ULTIMATE DISTRIBUTION OF THE

BEETLE IN NORTH AMERICA

The probable ultimate distribution of the beetle on the North American Continent is a matter of much interest and concern. It is believed

that, apart from the ocean barrier, temperature and precipitation are

tlie most important factors modifying the spread of the beetle beyond

its present range.

Temperature and Moisture Requirements of the Beetle

A temperature between 63° and 82° F. in the upper 3 inches of the

soil is lequired for the eggs to hatch and the young grubs to develop
normally. There is some embryonic development at 54° F., but the

eggs do not hatch. Eggs kept for the greater part of their development at 75° F. hatched at 54° F., but unless the young grubs were

transferred to a temperature above 63° F., they died within a few

days, probably because at 54° F. they were too sluggish to feed.

Newly hatched grubs do not endure a temperature of 91° F. Tlie

second- and tliird-instar grubs develop normally at temperatures between 50° and 95° F.; they are practically dormant at temperatures

below 50° F. The grub becomes progressively more cold-hardy as it

develops. Third-instar grubs can endure a temperature of 15° F.,

providing the temperature of the soil is reduced slowly and thawing

is gradual. Rapid freezing or thawing is fatal. Although grubs

have transformed into pupae and emerged as adult beetles at temperatures of 55° and 95° i ., many of the adults at these extremes of temperature were abnormal in that they were unable to shed the pupal

skin entirely and tlie wings did not unfold.

A study during the summer months showed that the rainfall must

be about 10 inches and uniformly distributed during that period for

the eggs to hatch and the young grubs to develop normally in the soil.

The egg must have moisture to bring about the swelling which is an

essential prelude to embryonic development. The newly hatched grub

must have adequate moisture to survive. It is more vulnerable to dessication than the older grubs because its more lightly chitinized skin is

less efficient in conserving body moisture, and it is less able to burrow

deeper into the soil in search of moisture. A deficiency of rain during the summer invariably causes a reduction in the population developing in the soil. Rainfall deficiencies in the fall and spring are less

important because the older grubs are more resistant to drought.

In most areas at present occupied by tlie beetle, the air temperature

during the winter frequently ranges below the lethal temperature of

15° F., but the temperature below the surface of the soil is reduced

only gradually below freezing. Precipitation indirectly affects the

temperature of the soil. A blanket of snow serves to keep the temperature of the soil within a few degrees of 32° F., well within the cold

tolerance of the grubs, even during prolonged periods of intense cold.

On the other hand, a freezing rain on ground not covered by snow

results in the formation of ice to a depth of several inches and causes

a high mortality of the grubs.

Western Spread of the Beetle

A study of the climatological data indicates that the beetle can

spread westward naturally to about the 100th Meridian into North

Dakota, South Dakota, Nebraska, Kansas, Oklahoma, and Texas. In

parts of the central Mississippi River Valley, where rainfall during the

summer averages from 2 to 4 inches less than on the Atlantic Seaboard,

and droughts tend to be more frequent and severe, the beetle may have

some difficulty in becoming established, and populations are likely to

increase slowly. The grubs probably could not survive the winter in

much of Wisconsin, Minnesota, North Dakota, and South Dakota, and

in northern Iowa and northeastern Nebraska because of the very low

temperatures and the light precipitation. In that area the temperature in the soil normally goes below the fatal 15° F. during the

winter.

7

645364 0—82 2 '
West of the 100th Meridian to the higher mountain ranges the country is too dry during the summer for tlie beetle to survive. In the

western mountain ranges precipitation is adequate but the summers

are too cool for development of the insect. , j

The cool summers and generally scanty rainfall m Washington and

Oregon are not favorable for the beetle. In central and southern

Cali'fornia temperatures are favorable throughout the year, but the

low precipitation during the summer would prevent the beetle from

becoming established, except in irrigated areas.

Southern Spread of the Beetle

There seems to be no climatological barrier to the spread of the

beetle into Florida and along the Gulf Coast into Alabama, Mississippi, Louisiana, and eastern Texas. In tropical and subtropical

Florida, where the temperatures are well within the limits for development of the insect, and rainfall is copious, the beetle would not only

be able to survive ; there probably would be two generations a year.

Northern Spread of the Beetle

The northern limits of spread of the beetle in the eastern half of

the United States will probably be in the more elevated sections of

northern New England and New York and in northern Michigan.

In these areas, the low temperatures of late spring and early summer

would so retard development of the insect that emergence and egg

deposition could hardly occur before August 1. Although the eggs

might hatch, it is unlikely that the grubs could survive. Elsewhere

along the Canadian border the beetle could spread in the southern

parts of the Provinces of Ontario and Quebec, into the interior to

Georgian Bay, and along the St. Lawrence Eiver to Montreal. In

southern New Hampshire, Vermont, and Maine, where the beetle is

established, some of the grubs require 2 years to mature and complete

their life cycle.

Even in those areas where the temperature and precipitation are

favorable for the beetle, there may be some ecological factor that would

inhibit its development. The grubs thrive in soils where the pH is

between 4.0 and 6.0; the populations are reduced in alkaline soils.

They develop better in well-drained loams and sandy loams than in

the heavy clay loams or the sands. The vegetation also influences the

buildup of populations. The beetle tends to become well established

and increase in abundance in those areas devoted to grazing, general

agriculture, truck crops, and fruit growing; it does not invade heavily

forested land, but it may be found" in open spaces in the woods.

HOW THE BEETLE SPREADS

The adult beetle is a strong and vigorous flier. It is especially

active on warm, sunny days. Beetles usually fly short distances from

plant to plant and from place to place in search of suitable food. It

is not uncommon for them to fly one-half mile or more against the wind

from a pasture to an orchard of ripening fruit. Very little flying

occurs when high winds are blowing, or on rainy days.

Occasionally there have been mass flights of beetles from the infested area. For several years there were flights across the Delaware

8
Eiver from New Jersey into the downtown sliopping and market

districts of Philadelphia, Pa. It is not known how far a beetle can

fly m sustained flight. In 1929, when the population reached its

peak in southern New Jersey, millions of beetles flew out to sea and

annoyed ñshing parties even 5 miles offshore. Later, they were washed

up dead and dymg in windrows on the beaches of the shore resorts.

Beetles have been observed in flight several hundred feet above

the ground ; when flying with the wind such beetles could be carried

long distances.

After periods of heavy rain beetles have been observed floating

down streams on pieces of wood and other debris. Beetles are able to

float on water for several hours. In 1933 many beetles were carried

by wind from New Jersey out over lower Delaware Bay. Many of

them dropped into the water. After falling into the water, they

drifted about until washed up on the opposite shore in Delaware.

Beetles have floated across New York Bay from New Jersey to Long

Island.

In the progressive spread of the infested area during the period

from 1921 to 1962, the beetles moved outward each summer at a rate

of 5 to 10 miles a year.

There is always danger of beetles being carried long distances to uninfested areas~by automobiles, boats, freight and passenger trains, and

airplanes. Beetles have been carried from the east coast to the west

coast in a few hours by jet plane. They fly into these transportation facilities during the process of loading ; or passengers may carry them on

thßir clothing or baggage. Adult beetles may be transported in containers of fruit or vegetables and other agricultural commodities.

The eggs and grubs may be carried in soil about the roots of plants.

Quarantines have been in force for many years to restrict this artificial dispersion of the beetles. That dispersion of the beetle has not

been more widespread in the United States during the past 45 years

may be credited to the enforcement of restrictions of the Federal and

State' quarantines on the movement of various carriers and products.

SEASONAL HISTORY AND HABITS

Normally the beetles begin to emerge from the soil the third week

of May in central North Carolina ; the first week of June in Virginia ;

about the middle of June in Maryland and Delaware; the third week

of June in New Jersey, Ohio, West Virginia, and southeastern Pennsylvania; the last week of June in New York, Connecticut, Ehode

Island, and Massachusetts; and the first week of July in southern

Maine, southern Vermont, and southern New Hampshire. On reaching the surface of the ground, the beetles usually fly to, or climb on,

some low-growing plants nearby and begin to feed. Mating of the

sexes may occur soon after emergence and is repeated at frequent

intervals throughout the life of the individual, which is usually 30

to 45 days. Mating usually takes place on plants, but it may occur

on the ground. When the population is dense, several males may

attempt to copulate with a female as soon as she emerges from the

ground. The congregated mass of beetles resembles an animated ball ;

each mass is composed of a single female and from 25 to 300 male

beetles.

On warm, sunny days the beetles feed and fly vigorously. They

are naturally gregarious, and tend to collect and feed on certain plants,
leaving other plants of the same variety, apparently equally attractive,

untouched. Late in the afternoon the females usually enter the

gromid to lay their eggs ; they may come out of the ground the followmg morning or remain in the soil for 3 or 4 days. They prefer to lay

their eggs in moist, loamy soil covered with closely cropped grass such

as in lawns or pastures, but some eggs are deposited in cultivated

areas. During periods of drought the female beetle seeks the moist,

more friable spots to lay her eggs ; most of the eggs may then be deposited on the watered greens of golf courses rather than over the course,

and in cultivated fields rather than in dry, hard pastures. After burrowing to a depth of 1 to 4 inches, the female deposits 1 to 4 eggs at

one time, and after an indefinite period in the soil, she returns above

ground to resume feeding. This procedure goes on until 40 to 60 eggs

have been laid. The peak of the beetle population in an area is usuaUj

reached 4 to 5 weeks after the initial emergence, but since some individuals emerge later than others, beetles may be present in an area for

4 months, or until frost.

The eggs hatch about 2 weeks after they are laid. The grub forms a

cell in the soil slightly larger than its body and feeds on fine rootlets.

It usually follows the course of the rootlets until these are consumed.

The grub passes through three stages, or instars, before reaching

maturity. The change from one instar to"the next is accompanied by

a shedding or molting of the skin. The first molt usually occurs 2 to

3 weeks after the young grub emerges from the egg ; the second molt,

3 to 4 weeks later. Most of the grubs are full grown in the fall, and

reach maturity in the spring. Then, after spending about 10 days in

the inactive prepupal condition, they change to the quiescent pupal

stage within their earthen cells. This stage lasts 8 to 20 days, depending upon the temperature and other conditions. The final transformation then takes place, and the adult beetles emerge from their pupal

skins and make their way to the surface of the ground. The entire life

cycle in southern New Jersey, which is shown diagrammatically in

figure 7, requires 1 year. In the northern infested areas, some grabs

require 2 years to complete their life cycle; in the extreme southern

areas, there is a possibility of two generations a year.

In southern New Jersey the beetle population in the soil is dominantly eggs in July, first- and second-instar grubs in August., secondand third-instar grubs in September, third-instar grubs from October

to May, and third instars, prepupae, and pupae in June. Further

information on the average composition of this population over an 11-

year period is given in table 1. The development of the population is

accelerated in the southern parts of the infested area, and retarded in

the northern parts.

During the summer and early fall the grubs feed mostly within the

upper 3 inches of soil ; in lawns and pastures they are close to the surface of the ground. When the mean temperature of the soil near the

surface falls to about 60° F., some of the grubs begin to move downward; movement ceases when the soil temperature reaches 50° F.

During the winter about two-thirds of the grubs are found within the

upper 4 inches, and less than one-twentieth of them below 6 inches.

They tend to go somewhat deeper in cultivated fields than in permanent turf, probably because the soil is looser and easier to dig through,

and the roots of the plants go deeper. In the spring as the soil becomes warmer the grubs move upward to the 3-inch layer and resume

feeding.

10
JAN. FEB. MAR. APR. MAY JUNE I JULY j AUG. | SEPT. . OCT.

BEETLES FEED ON FOLIAGE AND FRUIll

NOV.

<rie¿/3 /// ^//^r£/e ¿ïfZ/.- S¿/jeP>9C£ TU /^££û

C£££ A/^P

P^£.^/fje£S

rû P¿//^r£.

s¿£r¿f i/^f^p

DEC.

(?e¿/Bj' ^e£ //ííyvz>^

6ie¿/ffS cuA^r//y¿/£ rû r'££¿? £¿'i¿. û^OJTA^ ^/YZ?

£û(?s M^rû^. \.^/v¿? ff^o/^.e^P/pirr \ eo TE? Pfpr/zö" -^ ro s

rûéWiP£££ûm\ /A'^é/Ay ro purrs' û£ \/A^CI¥£S sfiû»"s¿/'e/5^C£

¿/r/à'(? ßuurs Pá^JVTS /S /fûsr Cû^/^ûA' \ ro /?^ss /f^/A^r£je //v

û£ p/^/^ry \^rrws r//^£. ! £^er//£/ir C£/.á. .

FiGUïtE 7.—Seasonal life cycle of the Japanese beetle in southern New Jersey.
TABLE 1.—Composition of the beetle population in soil in southern

New Jersey throughout the year

Percent of population as—

Month

Egg

Grub

Prepupa Pupa

1st

instar

2d

instar

3d

instar

Adult

July _- - -- 55

8

(*)

(*)

15

31

2

(*)

1

55

29

7

7

6

5

(*)

3

6

69

93

93

94

95

40

2 9

(*)

15

(*)

(*)

25

(*)

June 1 28 6

*Less than 1 percent.

FEEDING BY ADULT BEETLE

Type of Feeding

In feeding on the foliage of most plants, the beetles chew out the

tissue between the veins, leaving a lacelike skeleton, as shown in figure

8. On some plants with thin leaves and fine venation, and on petals

of roses and other flowers, where the delicate veins are not unpalatable, the beetles cut out and consume large, irregularly shaped portions

in the same manner as a caterpillar. Plants with thick, tough foliage

are usually free from attack, but when such leaves are eaten, the feeding is restricted to nibbling on the upper surface and does not penetrate to the lower surface of the leaf. Severely injured leaves soon

turn Brown and drop.

Factors Influencing Feeding

The beetles are most active and feed most extensively on warm,

clear, summer days between 9 a.m. and 3 p.m. Early in the morning

they are usually resting quietly on the plants, although some slight

feeding may occur at that time. When the temperature reaches

about 70° F., they begin to fly in all directions and to collect on the

more favored plants m the vicinity. Feeding is heaviest at temperatures between 85° and 95° F. The beetles become inactive at temperatures above 95° F., and often seek shade by crawling to the underside of leaves. A relative humidity above 60 percent retards nymg

and induces the insect to feed extensively. Late in the afternoon

feeding and flying slacken and the beetles become quiet for the night

There is little feeding or flying on cool, windy days or on cloudy days,

and no activity on rainy days. The beetle is very responsive to a

change in the weather ; a passing cloud will cause a beetle in flight to

seek a suitable resting place immediately.

12
J-1103b

FIGURE 8.—Leaves of Norway maple destroyed by feeding of the Japanese beetle.

The soft tissue has been eaten, leaving the network of veins.

The beetles prefer to feed on plants exposed to the direct rays of the

sun. Plants m shade are never fed on so heavily as those in the sun.

Plants in close-growing woods are rarely attacked. Usually the beetles

begin to feed on the upper and outer foliage and work downward. By

the time one-half to two-thirds of the foliage on a tree has been consumed, the beetles may leave and congregate on other plants in the

vicinity, or they may continue to feed until the tree is completely

defoliated.

The attractiveness of various plants to the beetle changes during

the summer. When beetles first emerge in an area, feeding is usually

confined to low-growing plants such as roses, zinnias, smartweed, sassafras, and grapes, and there is much flying from plant to plant. In

areas of dense population, feeding on these plants may continue until

practically all of the foliage has been consumed. However, about 2

weeks after the initial emergence, the beetles tend to leave the lowgrowing plants and go to the fruit and shade trees. They may feed

on the trees for several weeks, but as the leaves become older and

tougher, they return to the more-succulent, low-growing plants. Most

of the damage to asparagus, corn, clover, and other succulent plants

occurs after the beetles have left the trees.

In general, the degree of feeding on any plant will depend upon its

attractiveness to the insect and upon the abundance of beetles in the

vicinity. It is not known why some species of plants are preferred

and other closely related species are practically free from attack.

13
Beetles are attracted to succulent flowers and foliage, but all succulent

plants are not attacked. They are attracted by ripening fruit and to

plants with a high content of reducing sugar. When there are only

a few hundred beetles in the vicinity, the beetles attack usually only

the most preferred plants, but when several million are present, the

feeding is on all favored plants, and on those rarely attacked.

Toxic Plants

The public has called attention from time to time to plants that were

believed to be toxic to the beetle. The usual evidence was the presence

of a large number of dead beetles on the ground beneath a plant on

which they had been feeding. After mid-summer when many beetles

have lived their normal span of life, it is not uncommon to find dead

beetles beneath all plants on which they are feeding. In most cases

it was not possible to demonstrate experimentally that the plants had

constituents toxic to the beetle. A few plants were found to have some

toxicity to the insect.

Beetles feed readily on the flowers and foliage of cultivated geramums, Pelargonium spp., and often become paralyzed and drop from

the plants. Some die, but many recover within 24 hours. The flowers are more toxic than the foliage; plants in sunlight have a higher

toxicity than those in the shade.

The castorbean, Bicinus communis, is not one of the most favored

plants. The beetle attacks the foliage and flowers of the varieties

Sanguineus and Zanzibariensis, but it has not been observed feeding

on the other varieties. These two varieties appear to be mildly toxic

to the beetle.

The flowers of the bottlebrush-buckeye, Aesculns paryißora, are

very toxic to the beetle, but the foliage has little toxicity. if the

beetles feed long enough on the flowers, they become paralyzed and

eventually die. The buckeye is in bloom when the beetles are in

flight; the horsechestnut, A. hippooastanum, is in bloom before the

beetles appear. It is possible that the flowers of horsechestnut are

toxic to the beetle.

Small Fruits

The fruit and foliage of blackberries, huckleberries, blueberries, and

raspberries are eaten by the beetle. The injury to one-crop varieties

of raspberries such as Latham is not usually of economic importance,

but the feeding on the growing tips of Eanere and other two-crop

varieties may reduce seriously the second crop. Ripening blueberries

are attacked vigorously ; after the fruit is harvested, the feeding continues on the new succulent foliage.

The foliage of all varieties of grapes is preferred food for the

beetle; the foliage is frequently skeletonized (fig. 9). The beetle

attacks the fruit of such early-ripening varieties as Clinton, Delaware,

Niagara, Muscat, and Portland, but it usually does not damage the

immature fruit of late-ripening varieties. However, unless the grape

berry moth and black rot are controlled in a vineyard, the beetle is

likely to attack even the immature berries.

The beetle feeds on the foliage of red currant, cranberry, and strawberry, but the damage usually is not of economic"importance. It rarely

attacks gooseberries.

14
i'iGUEE y.—Japanese beetles feeding on a grape vine.

Tree Fruits

The foliage of apple, cherry, and plum is very attractive to the

beetle ; feeding is often extensive on these trees. The foliage of peach,

nectarine, and quince is less attractive, but considerable damage may

be done. Pear and persimmon trees are rarely attacked. Eipening

or diseased fruit is particularly attractive to the beetle ; the foliage of

trees with such fruit is eaten more extensively than that of trees with

sound immature fruit, or without fruit.

Crops that mature before or after the beetles are abundant in an

area are not usually injured seriously. Cherries are often picked

before many beetles appear. There are few beetles around to injure

the maturing fruits of late-ripening peaches and apples.

The fruits of apple, peach, nectarine, plum, and quince, that mature

when the beetle is abundant, are often damaged seriously. Very little

feeding is sufScient to lower the market value of the fruit, but at

times the beetles gather on the fruits in such large numbers as to cover

them completely (figs. 10 and 11) and feed until nothing edible is

left. The beetle is very fond of such apples as Yellow Transparent,

Starr, Williams, and Red Astrachan. The injury is most severe on

peaches of the Cumberland, Raritan Rose, Triogem, and Sunhigh

varieties; moderate on Redrose, Goldenglobe, Summercrest, and Goldeneast ; and light on Elberta.

Truck and Garden Crops

Corn is one of the preferred plants of the beetle. The leaves and

tassels are sometimes eaten, but the silks of both field corn and sweet

corn are highly attractive. Masses of beetles collect on the maturing

silk and cut it off as it grows (fig. 12) ; this prevents the pollination

of many embryonic kernels and results in malformed kernels and

reduced yield.

15
J-3049

FIGURE 10.—Japanese beetles feeding on the fruit and foliage of peacb.

FiauEE 11.—Japanese beetles feeding on the fruit and foliage of apple.

J-T601

16
FiGUBE 12.—Japanese beetles feeding on the silk of com.

The beetles feed extensively on asparagus and do much damage to

the young leaflets and to the epidermis of the branches and stalks.

Several hundred beetles sometimes collect on a single plant and bend

it over by their weight (fig. 13). Extensive feeding weakens a plant

and reduces the yield the following spring.

Beetles often feed heavily on the leaves of rhubarb (fig. 14). At

times the foliage of limai beans and bush beans is severely attacked.

The feeding is usually light on okra, beets, broccoli, cabbage, brussels

sprouts, white mustard, turnip, endive, watermelon, cantaloupe, cucumbers, pumpkin, squash, artichoke, carrots, sweetpotato, garden

peas, eggplant, salsify, parsley, and catnip. The beetle rarely attacks

onions, leek, cauliflower, rutabaga, kale, redpepper, lettuce, tomato,

radish, or spinach.

Field Crops

Field com and soybeans (fig. 15) are the only field crops severely

damaged by the beetle. The soybean varieties Richland, Earlyana,

Lincoln, and Mingo are usually the most attractive, and Chief, lUini,

Gibson, and Viiing the least attractive, but the varietal preferences

of the beetle may change from year to year and from place to place.

Beetles feed moderately on the foliage and blooms of alsike clover,

red clover, and alfalfa, and lightly on whiteclover. They rarely attack timothy, buckwheat, oats, barley, rye, millet, wheat, tobacco,

potatoes, or vetch.

17
J-2822

FiGUEE 13.—Japanese beetles feeding on asparagus plants.

FIGURE 14.—Japanese beetles feeding on rhubarb.

J-289«

18
FiGUBE 15.—Japanese beetles feeding on soybeans

J-3718

Ornamental Herbaceous Garden Plants

The beetle is very fond of the blooms of hollyhock, dahlia, marshmallow, rosemallow, common mallow, evening-primrose, white

thorough-wort, and zinnia. It feeds lightly to moderately on corncockle, calendula, carnia, gladiolus, sunflower, flower-of-an-hour, St.

Johns-wort, morning-glory, cardinal-flower, four-o'clock, lotus, yellow

oxalis, peony, garden geranium, Japanese fleeceflower, castorbean,

scarlet sage, marigold, bracken, and cinnamonfem. It rarely attacks

asters, chrysanthemum, pxeye daisy, pampasgrass, cosmos, gaillardia,

gardenia, strawflower, daylily, iris, purplue loosestrife, beebalm. petunia, phlox, spiderwort, or verbena. It has not been observed feeding on ageratum, snapdragon, columbine, wild-indigo, begonia, caladium, cockscomb, dusty-miller, cornflower, mountain-bluet, turtlehead,

lily-of-the-valley, coreopsis, crassula, larkspur, sweet-william, clover

pink, bleedingheart, foxglove, California poppy, Icelajid poppy, Chileavens, gypsophila, coralbells, plantainlily, candytuft, garden balsam,

lantana, perennial peavine, sweetpea, forget-me-not, flowering tobacco,

lions-heart, portulaca, mignonette, coneflower, scabious, sedum, nasturtium, mullein, speedwell, violet, or pansy.

Ornamental Shrubs and Vines

The rose (fig. 16) is perhaps the most attractive of the ornamental

shrubs to the Japanese beetle. Not only are the fully developed

flowers unusually attractive to them, but the buds, as soon as they show

19
FIGURE 16.—Japanese beetles feeding on a rose bush.

J-2736

the color of the petals, are also subject to attack. Beetles feed on the

blooms and foliage of roses throughout the summer. Usually the

white and yellow roses are damaged more extensively than those of

darker hues. The beetles also severely damage bottlebrush-buckeye,

summersweet. shrub-althea, kerria, orapemyrtle, Japanese floweringcrab, Japanese plum. Oriental cherry, Virginia-creeper, and Japanesecreeper. They feed lightly to moderately on aralia, Hinodegiri azalea,

spicebush, Japanese barberry, European barberry, trumpetcreeper,

butterfly-bush, buttonbush, flowering quince, deutzia, weigela, pearlbush, wisteria, lespedeza, California privet, bayberry, kudzu vine,

spirea, and viburnum. They feed rarely on ailanthus, torch azalea,

Chinese azalea, swamp-azalea, clematis, English ivy, climbing hydrangea, winterberry, European privet, honeysuckle, matrimony-vine,

rhododendron, elder, or European bush-cranberry. Beetles have not

been observed feeding on bamboo, common box, beauty-berry, sweetshrub, American bittersweet, Chmese redbud, dogwood, evergreeneuonymus, forsythia, smooth hydrangea, panicle hydrangea, American

holly, mountain-laurel, mockorange, Japanese pieris, Ajnerican bladdemut, snowberry, coralberry', lilac, or tamarisk.

Shade Trees

The beetles feed extensively on Japanese m^aple, Norway maple,

horsechestnut, gray birch, American chestnut, black walnut, London

planetree, Lombardy popular, pussywillow, American mountain-ash,

American linden, littleleaf linden, European linden, American elm,

English elm, and Chinese elm, and when abimdant may practically

defoliate the trees. Tliey feed lightly to moderately on sycamore

maple, sugar maple, black alder, white birch, mockemut hickory,

southern catalpa, hawthorn, American beech, European beech, Carolina silverbell, Siebold walnut, European larch, túpelo, American

20
planetree, scrub oak, chestnut oak, pin oak, weeping willow, heartleaf

willow, bald-cypress, silverpendent linden, silver linden, and slippery

elm. They rarely attack boxelder, pignut hickory^ shagbark hickory,

American hazelnut, smoke tree, cryptomeria, gmkgo, witch-hazel,

butternut, Chinese juniper, common juniper, eastern redcedar, American sweetgum, Virginia pine, white oak, scarlet oak, post oak, eastern

red oak, southern red oak, black oak, locust, American arborvitae or

Oriental arborvitae.

The beetles have not been observed feeding on white fir, red maple,

silver niaple, false cypress, white ash, green ash, tulip tree, southern

magnolia, sweetbay magnolia, red mulberry, Norway spruce, Oriental

spruce, Colorado spruce, Scotch pine, eastern white pine, white poplar,

or Canada hemlock.

Noneconomic Plants

If the beetle did not have fruit, cultivated crops, and ornamental

plantings available, it could make out well on the numerous weeds and

other plants of little value. Pennsylvania smartweed (fig. 17), sassafras, poison ivy, summer grape, and fox grape are very attractive to

them. If beetles are in an area where these plants grow, they are

more apt to feed on them than on other wild plants, particularly early

in the summer. They feed lightly to moderately on velvetleaf, copperleaf, ragweed, dogbane, partridgepea, chicory, crabgrass, fleabane,

bedstraw, snapweed, butter-and-eggs, toadflax, spatterdock, Virginia

arrow-arum, broadleaf tearthumb, combind, hedge knotweed, marshpepper smartweed, princesplume, ladysthumb, spotted ladysthumb,

hedge combind, pickerelweed, ohokeberry, curly dock, bitter dock,

shining sumac, meadowbeauty, arrowhead, goldenrod, cattail, and

ironweed. They also feed occasionally on amaranth, milkweed, lambsFiGURE 17.—Japanese beetles feeding on smartweed.

21
quarters, goosefoot, Canada thistle, flat-sedge, joe-pye-weed, quickweed, tickclover, plantain, stagliom sumac, greenbrier, and germander.

FEEDING BY GRUBS

The grubs feed on the roots of a wide variety of garden and field

crops, ornamental plants, and grasses, but they do not thrive in plantings of whiteclover, red clover, alsike, sweetclover, alfalfa, soybeans,

buckwheat, or orchard grass. The feeding of the grubs on the underground stems and roots may not be suspected until the plants are badly

damaged.

The grubs are most abundant in well-kept lawns, and in pastures

and golf courses. They prefer the tender grasses to the tougher

varieties of grass and other plants. As a grub burrows through the

soil just below the surface, it cuts off and consumes the grass roots.

When there are more than 10 grubs per square foot of turf, and there

is a deficiency of rainfall, there may be several areas of dead brown

grass in the sward by September or early October (fig. 18), that can

be rolled back easily with the fingers (fig. 19), but the damage may not

appear until the following spring.

If there is a limited supply of food, as m cultivated fields, the grubs

move about considerably, and may travel laterally as much as 10 feet.

They tend to collect about the roots of plants; very few are found in

unplanted spots. When there is a dense jjopulation, the grubs damage

seedling corn, beans, cabbage, tomatoes, and other truck and garden

crops. Extensive feeding on the roots of even well-established plants

reduces their vitality and may afl'ect the yield. Grubs have destroyed

many plants in nursery seedbeds, and have killed 50 percent or more of

the plants in strawberry beds. They also severely injure some varieties of ornamental nursery stock by girdling the main roots at depths

of one-half to one and one-half inches below the surface of the ground,

and consuming the roots (fig. 20).

J-2392

FiGUEE 18.—A lawn damaged by the feeding of Japanese beetle grubs on the

roots of grass.

22
Í^M'^^-SSS?S^aF'SíÍa!Íít;ÍA#?S.ySi«?'75^:^-ÍV..;^^

J-2010

FiBURE 19.—Japanese beetle grubs exposed when injured turf is rolled back.

FieuKE 20.—Plants killed by the feeding of Japanese beetle grubs on their roots.

23
NATURAL ENEMIES OF THE BEETLE

Native Enemies

When the beetle became established in New Jersey, the insect-feeding

birds, small terrestrial animals, and the few predaceous and parasitic

insects indigenous to the region were not sufficient to cope with its

20- to 30-fold reproductive potential.

Chickens, ducks, turkeys, and guineas, and a few wild birds among

which are the purple grackle, the European starling, the cardinal, the

meadow lark, the catbird, the house sparrow, the robin, and the ringnecked pheasant feed on adult beetles. The domestic fowl, the European starling, the purple grackle, the crow, and gulls also dig and devour large numbers of grubs, especially when fields are being plowed

and when grubs are close to the surface m grasslands.

Toads eat a great many beetles. Among the terrestrial mammals,

the common mole, the star-nosed mole, the short-tailed shrew, the

skunk, and possibly the pine mouse feed on grubs. The predaceous

ground beetles, the horse-flies, and the stilleto-flies will attack the

grubs when they encounter them, and robber flies and ants have been

observed feeding on both adults and grubs.

Practically none of the native parasitic insects attack the beetle.

The wasp Tiphia intennedia Mall, sporadically parasitizes a small

proportion of the grubs, and a fly, PtUodexia sp., has been observed

attacking them. Although these native enemies have, from time to

time, reduced the beetle population within a limited area, their efforts

are too sporadic and too restricted to have much effect on the population within a region.

During the first 12 years following discovery of the beetle, the annual populations in southern New Jersey increased rapidly in magnitude and importance. In some places the turf had a population of

150 grubs per square foot. "Wlien the population reached its peak

density in that area in 1929, it was estimated that there were more

than 600 million adult beetles per square mile. Then, the annual populations began to decline until by 1945 the beetle was of only mmor

economic importance in southern New Jersey, except in a few isolated

areas. This cycle of rise and decline in population has been repeated,

with modifications, as the beetle has invaded new areas.

When the beetle population began to decline in southern New Jersey, it was thought at first that the reduction might be due to a deficiency of rainfall at the time the eggs were hatching, but the decline

continued even when rainfall was favorable for development of the

grubs. It was evident that some other factor was restoring the biological balance in the region. Two new biotic agents—imported parasitic insects and native diseases—were becoming established, and it is

known now that they were largely responsible for the progressive decimation of the beetle population.

Imported Parasitic Insects

A search for the enemies of the beetle in Japan and elsewhere was

carried on from 1920 through 1933. It was found that a large number

of insect parasites and predators attack the various stages of the

Japanese beetle and related species in the Orient. During that period

1% million predaceous and parasitic insects of 49 species were collected

24
in Japan, Korea, Formosa, China, India, Australia, and Hawaii, and

shipped to the Department's laboratory in New Jersey.

Five of the imported parasitic insects have become established in

the eastern United States and are a part of the permanent fauna of

the region. These species are Hyperateina aldrichi Mesnil. {Centêter

omerea Aid.), a parasite of the adult beetle, and Dexilla ventralis

(Aid.), Prosena siberita (F.), Tiphia popilliavora Rohw, and Tiphia

vemalis Rohw. which parasitize the grubs. The most eflective and

widely distributed of these species are T. vernalü (fig. 21), which

attacks overwintering grubs in the spring, and T. popilliavora, which

parasitizes the grubs of the new brood in late summer.

The female Tiphia wasp searches out a grub in the soil, stings it to

cause temporary paralysis, and attaches a single egg to its underside.

The maggotlike larva hatching from the egg remains attached to the

grub, sucking blood and feeding on it. The yoimg parasite attains full

growth within a few days, by which time the grub has been consumed

except for the head capsule. The parasite larva then spins a strong,

watertight, silken cocoon within the earthen cell formerly occupied by

the grub and the following year emerges as an adult.

Under favorable conditions T. vemalis has parasitized over 60 percent of the grubs in an area ; T. popilliavora is somewhat less eiïective.

There is no doubt that these two wasps have important parts in the

biological control of the Japanese beetle. The other imported parasitic insectsJiave a lesser role.

J-2932

FIGURE 21.—Tiphia vemalis, a wasp that lives on and destroys Japanese beetle

grubs. About six times natural size.

25
Entomogenous Diseases

Diseases were found occasionally among Japanese beetle grubs as

early as 1921. Although these diseases were not identified specifically,

they were determined to be mainly of bacterial and fungous origiii.

By 193.3 large nimibers of infected grubs were found in certain areasin

New Jersey, Delaware, and Pennsylvania. About 25 difl'erent soil

microorganisms can infect some stage of the Japanese beetle; among

these are fungi, protozoa, nematodes, and bacteria.

Fungi

Metarrhisium anisopliae Metsch., the green muscardine, was found

attacking Japanese beetle grubs in 1921. Since then grubs infected

with this fungus have been found from time to time throughout the

beetle-infested area. Although this fungus is widely distributed

naturally, the incidence of infection among the grubs is usually low.

There is no doubt that the sporadic and small but continuous occurrences of this disease among the grubs have a beneficial effect, even

though they may rarely bring the beetle under control.

Metazehisiimi ghitinosum Pope is also pathogenic to the grubs.

This fungus probably has about the same limitations as M. anisopliae.

Isaria densa Auct., a pathogen of Melolontha spp. in France,

infected grubs introduced into inoculated soil imder experimental conditions, but the disease has not been used successfully in the field.

The spores of Beauveria hassiana (Bals.) Vuill. appear to have little

pathogenicity to the grubs, but adult beetles allowed to feed on foliage

sprayed with a dilute suspension of spwres become infected. Healthy

beetles kept in close association witli infected beetles soon contract the

disease. Although this disease occurs sporadically in areas where the

fimgus was colonized, it is probably of little importance in the control

of the beetle.

Protozoans

In 1950 Japanese beetle grubs infected with a microsporidian were

found at Warrenton, Va., but since then no cases of this disease have

been found there, or elsewhere within the beetle-infested area. The

possibilities of a microsporidian disease for the control of the beetle

have not been investigated.

ISematodes

In the spring of 1929, Japanese beetle grubs infected with a nematode, Neoaflectana glasen Steiner, were fovmd at Haddonfield, N.J.

Later parasitized pupae and adult beetles were found in that area.

Since N. glmeri is a general parasite of insects, but not pathogenic to

plants, it appears that it had adapted itself to the Japanese beetle.

Although a search was made in other parts of New Jersey and in

Pennsylvania, it was not found at that time in any other area.

The infective, second-stage nemas enter the grub by way of the

moutli, develop two or three generations within the body, and destroy

their host by feeding on the tissues. They continue to develop in the

cadaver of the grub until most of the tissues have been consumed.

The grub at death is flaccid, of a reddish-brown color, and swarnung

with nemas, most of them in the second stage ready to invade the sou

and infect another host. As many as 2,400 infective-stage nemas

26
have been recovered from a single grub, but the usual number is about

1,500.

N. glasen has been colonized in New Jersey and in Maryland.

This is one of the few instances in which nematodes have been

colonized for the control of an insect pest. It is spread slowly

through the soil by its own movement and by nema-infected grubs.

It may be carried considerable distances by infected adult beetles, by

birds and small mammals, and in the movement of soil by wind, water,

or man.

This nematode is not effective mider so wide a range of conditions

as the parasitic insects and the bacterial diseases, but in habitats

suitable for its development it has parasitized more than 50 percent

of the grubs.

Neoaplectana chresima Steiner also infects Japanese beetle grubs.

The biology of this species is similar to that of N. glaseri. Other

nemas infecting grubs of this beetle have been found occasionally in

the field. The possibilities of N. chresima and the other nematodes

for control of the beetle have not been investigated.

Rickettsias

A fatal infection of Japanese beetle grubs caused by Coxiella

popiUiae Dutky, one of the rickettsias, was discovered at Nottingham,

Pa., in 1940. It has since been encountered in grubs from several

widely separated areas. At some localities large numbers of diseased

grubs have been found repeatedly. The affected grubs have a

greenish-blue discoloration of the fat bodies, which led to its designation as blue disease. Attempts to colonize this rickettsia in other

areas have been only partially successful.

Bacteria

In 1921 it was recognized that bacterial diseases existed among

Japanese beetle grubs. In 1926 and 1927 several species of bacteria

were isolated from affected grubs, some of which proved to be highly

pathogenic. Only a few bacteria have been studied extensively, the

most important being the organisms causing the milky disease of the

grubs. ,

Milky disease was discovered in New Jersey in 1933, when a few

abnormally white grubs were found in the field, and microscopic

examination showed that the blood of these grubs was teeming with

bacterial spores. By 1938 milky disease was prevalent m the older

areas infested by the beetle, but it was not found m the more recently

infested areas. In 1940 it was demonstrated that this disease was

caused by two species of bacteria. Bacillus popillioe Dutky, and B.

lentimorhus Dutky. Bacillus popilliae is the better known, and

probably the more important. .

The origin of the milky disease organisms is not known. It is

probable that they are obligate parasites of the white grub family, the

Scarabaeidae, with the Japanese beetle being their most common host

These bacteria do not infect other insects, earthworms, warmblooded

animals, or plants. „ . ,, ., A„íI,„

The spore stage of B. popilliae normally occurs in the soil As the

grubs work thefr way through soil, feeding on roots and other vegetable matter, they ingest the spores along with the other mater ah

The spores germinate" penetrate the wall of the gut, and enter the

27
blood as the vegetative stage. Infection does not begin until the

vegetative forms of the bacterium appear in the blood. The bacteria

multiply in the blood, giving it a cloudy appearance. Just what induces sporulation is not known, but it occurs when the vegetative

forms become exceedingly numerous. Sporulation continues until

all the bacteria have reached the definitive spore stage, completing the

cycle. At that time the blood becomes milky white in appearance,

and usually contains more than 2 billion spores.

A close relationship exists between the development of infection

and the ability of a grub to metamorphose. It is possible for a grub

to molt before the bacterium has completed its cycle. If, at the

normal time of pupation, the bacterium is not in its final stage, metamorphosis proceeds in an apparently normal manner. In that case

sporulation occurs in the blood of the adult beetle. After the spores

appear in the blood of a grub, it does not usually develop further.

In contrast to many entomogenous, septicémie diseases, which kill

the host within a few hours or days, B. popilliae passes through a

slow, methodical course of development. Many grubs live for weeks,

or even months, after the blood has become loaded with spores, particularly at low temperatures. It is not uncommon for grubs that

become infected late in the fall to live until they resume activity in

the spring. Not only do infected grubs remain alive, but they continue to feed. As death approaches, the grubs become less active and

then moribund. At that time the circulation of the blood stops and

the bacteria settle to the bottom of the body cavity.

The spores of B. popilliae are very resistant to adverse conditions

and may remain in the soil for many years, ready to infect successive

generations of grubs. The spores remain alive after having passed

through the digestive tracts of birds and small mammals that have

eaten infected grubs. The potency of the spores is reduced when the

pH of the soil is less than 5.0, or they are exposed to ultraviolet light

or sunlight. Tliere is also some loss of potency when spores are heated

above 194° F., or kept under refrigeration in a water suspension.

The temperature for the development of B. popilliae seems to be

between 60.8° and 96.8° F. A temperature above 70° F. is required

for the rapid buildup of the pathogen in an area. In Virginia, a

definite buildup of the organism occurred in 1 year, but in Connecticut and New York, 3 to 4 years were required.

During the period from 1939 to 1953, an extensive program of

colonization of B. popilliae was conducted in cooperation with various

State and Federal agencies to accelerate the spread and buildup of

the pathogen. A^Hien that program was discontinued, the bacterium

had been colonized at 123 thousand sites in 14 eastern States and the

District of Columbia. A dense population of grubs and a high inoculum potential favor the establishment and the rapid spread of the

organism. The successful use of B. popilliae depends upon its transmission from grub to grub. Since the pathogen may be transmitted

from the grubs to the adult beetles, the adult beetles with their

migratory habits aid in the dispersion. The organism is also spread

by other insects, birds, skunks, and moles, and in the movement of infected soil.

Although widespread distribution of the pathogen was not undertaken until 1939, and only a small portion of the land in a given area

was inoculated, by 1945 there was a high incidence of the disease in

28
Connecticut, New York, New Jersey, Delaware, and Maryland, where

treatments had been applied early in the program. A surrey in the

fall of 1960 showed that the organism was well established and fmictionmg at many sites within the beetle-infested region.

Bacillus lentÍ7norbus, the other bacterium causing milky disease,

often occurs in close association with B. popüUae. The biology of

this species is similar to that of B. popilliae, but it has a more limited

range of temperature for its development. It also is an important

factor in the biological control of the Japanese beetle.

Serratia marcescens Bizio, a red-pigmented bacterium discovered

in 1951, 18 highly pathogenic to the grubs. This bacterium occurs

commonly m nature, but it probably is not an important factor in the

control of the grubs.

Bacillus alvei Ches, and Chey., the bacterium associated with European foulbrood of the honey bee, is also highly pathogenic to the

grubs. This pathogen has not been investigated further for the control of the beetle.

STATUS OF THE BEETLE IN 1962

Populations of beetles are increasing in those areas recently invaded

by the insect, but in those areas invaded prior to 1945, the populations

are generally small and of little economic importance, except in special

situations. In the older infested areas, the biological balance between

the pest and its natural enemies appears to be fairly well established,

but it is unlikely that the beetle will ever be eliminated by natural

control agents. Since the beetle has become a part of the permanent

fauna of the region, the density of the annual broods can be expected

to fluctuate to some extent from year to year, depending largely upon

whether the rainfall in the early summer is adequate or inadequate for

the hatching of the eggs and the development of the small grubs.

When the soil is moist during that period, invariably there are more

beetles in an area the following summer. However, it is not expected

that beetle populations will ever again build up to epidemic proportions in the older infested areas.

Even in the older infested region sporadic upsurges of the beetle

population can be expected in areas where parasites, diseases, and

other biotic control agents are not well established, or have been

eliminated inadvertently by man. In some areas where parasites and

diseases have been colonized, beetle populations have remained too low

for an adequate buildup of these biotic control agents, possibly because

adverse conditions, such as dry summers, prevented the buildup of

beetle populations. When conditions are suitable for development of

the beetle, a few years may elapse before disease and parasites are

sufficiently abundant to cope with it. The application of insecticides

to turf practically eliminates grub populations for several years,

thus preventing the establishment of parasites and disease in the

treated area, but when these chemicals have dissipated in the soil,

there is then no restraining factor to inhibit the buildup of a grub

population. Extensive grading operations at large housing developments generally eliminate any enemies of the beetle that might be

present originally in the surface layer of soil ; a few years may elapse

before these enemies become reestablished. Meanwhile, the large ex29
panse of unprotected turf at a housing development is conducive to a

rapid buildup of a local beetle population.

Protecting plants from the ravages of the beetle is now much easier

than in the early days of its invasion into the eastern States. The

insecticides then available were only partially effective in protecting

plants from attack by the adult beetle; little was known about the

control of grubs in the soil. Now, with light populations of beetles

in the older infested areas and potent insecticides available, it is

relatively easy to prevent them from doing extensive damage.

Foliage and fruit can be protected by timely applications of sprays

containing DDT, methoxychlor, Sevin, malathion, or parathion.

Lawns and golf courses can be protected for 5 or more years by a

single application of aldrin, heptachlor, dieldrin, chlordane, toxaphene, or DDT.

The Japanese beetle is no longer a serious menace to American

agriculture within the older infested area on the Atlantic Seaboard.

It is largely a nuisance and an annoyance to the suburbanites. With

its natural enemies preventing the buildup of enormous populations,

the beetle these days is no more difficult to control than many other

pests that attack plants.

30 U.S. GOVERNMENT PRINTING OFFICE. 1962 O—645364