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NATUR
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AL HISTORY

Digitized by the Internet Archive
In 2011 with funding from
University of Illinois Urbana-Champaign

http://www.archive.org/details/peachborermethod15flin

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STATE OE ILLINOIS

DEPARTMENT OF REGISTRATION AND EDUCATION

STATE NATURAL HISTORY SURVEY DIVISION

STEPHEN A. ForBEs, Chief

ENTOMOLOGICAL SERIES
CIRCULAR 8

THE PEACH BORER AND
METHODS OF. CONTROL

By W. P. FLINT AND S. C. CHANDLER

URBANA, ILLINOIS

U. OF 1c UB.

Nattura] History Survey
Library

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wo-)S THE PEACH BORER AND METHODS OF CONTROL

By W. P. FLINT AND S. C. CHANDLER

The peach borer* is, in most localities, the worst insect enemy of
the peach tree. Judging from recent experimental work, it can be

easily and cheaply controlled by the use of para-dichlorobenzene
fo. .B.).T

Fic. 1.

Trunk of peach tree injured by borer, showing mass of
gum and protruding pupal case of the borer.
It would be very difficult to find a five year old peach tree any-
where in Illinois that has not been injured by the peach borer.

This insect always passes the winter in the inner bark of the
peach tree as a pale white worm from one-quarter to one-half inch
* 4 egeria exitiosa Say.

As this name is difficult to remember and pronounce, it has been suggested that the abbreviation
P. D. B. (Painless Death to Borers) be commonly used in preference to the longer term.

4

in length. These worms will be found from ten inches above to
six inches below the surface of the soil. They are most abundant
just below the surface. Their presence in a tree is indicated by
masses of gum mixed with brown frass or sawdust exuding from the
injured trunk. (Fig. 1.) During the spring and summer the
worms feed on the inner bark of the trees. They become full grown
from the middle of June to the first of September. They then spin
cocoons of silk, incorporating in them bits of frass. In these cocoons
they change to a brown pupal stage, emerging from eighteen to thirty

Fic. 2. Moths of peach borer on leaves.

days later as clear-winged moths. The moths have much the
appearance of large wasps. (Fig. 2.)

The average life of the moths is six days, during which time
the female lays from four hundred to one thousand eggs. The
eggs are placed singly on or around the bases of the trunks of peach

5

and related trees. In from seven to ten days small white worms with
brown heads hatch from these eggs. They crawl over the outer
bark and on finding a crack or wound rapidly eat their way in to the
inner bark, where they continue to feed until cold weather. They
remain dormant during the winter and resume feeding in the spring.
(Fig. 3.)

There is but one brood a year, the moths emerging from July
to October. Records made at Centralia, Illinois, show that young
worms were hatching from July tenth to October tenth. At least
75% of the borers will hatch between the middle of August and the
middle of September.

The injury to the trees is caused entirely by the worms, or larvae,

Fie. 3.
Larva of peach borer enlarged (above) and natural size (below).

feeding and boring in the inner bark of the lower trunk and large
roots. The most serious injury is done to trees from two to four
years old. Borers may be found in trees of all ages.

Until 1919 the only effective means known for controlling the
borers was to cut or dig them out. This is best done after removing
the earth from around the base of the tree, when the borers may be
cut out with asharp knife, following the grain of the bark. Burrows
that can not be opened with a knife should be probed with a piece
of flexible copper wire. It is generally necessary to go over an
orchard twice each year, in October and in May. Care must be used

in cutting or the injury done in this way may be as great as that

caused by the borer. Even with thoro work it is seldom possible
to get more than 90% of the borers. At best it is a very unsatis-
factory method of control.

6

A far more effective and cheaper means of destroying this insect
has been discovered thru experiments of the Federal Bureau of
Entomology. This work was later taken up‘in Illinois and in other
states. The method consists in applying a small quantity of para-
dichlorobenzene (P. D. B.) crystals about the base of infested peach
trees, and covering them with earth. These crystals volatilize and
the gas from them, which is heavier than air, penetrates to the borers
and kills them.

During 1920 and 1921 the Illinois Natural History Survey con-
ducted a number of experiments in the use of this material. This
work was carried on at Urbana, Farina, Carbondale, Anna, Cobden,
and New Burnside. The para-dichlorobenzene was applied to
trees of all ages from those in the nursery row to those five years
old. Applications were made to blocks of trees at intervals during
the spring and fall. A detailed account of these experiments is being
published in the report of the Illinois Horticultural Society for 1921.

The information here presented regarding this method of treat-
ment is drawn largely from the experimental work above mentioned.
It can perhaps best be given by answering some of the questions
frequently received regarding it.

WHAT IS PARA-DICHLOROBENZENE (P. D. B.)?

Para-dischlorobenzene is a white crystalline substance, the
chemical formula for which is CsHisCl.. To get the best results in
borer-control the crystals should be fine enough to go thru a screen
with ten meshes to the inch.

How Does 1T KILL THE BORERS?

When exposed, in the air or in soil, to a temperature of 60° F. or
above, the small crystals of the para-dichlorobenzene change to a gas
which is heavier than air and penetrates the burrows of the borers.
Exposure to moderate amounts of this gas is fatal to insects. Man
and domestic animals are not injured except by prolonged exposure
or by taking the crystals internally.

How SHOULD IT BE APPLIED?

Para-dichlorobenzene should be applied to the cleaned surface
of the ground around the base of the peach tree. All large masses of
gum should be removed from the tree trunk. None of the crystals

7

should be placed against the trunk of the tree, or more than two
inches from it. Three or four spadefuls of earth should then be
placed over the crystals. It is not advisable to dig the earth away
from the tree before applying the para-dichlorobenzene. It will be
well in cultivating to throw the earth away from the trees, instead
of mounding it about them as has been generally done in the past.
This will cause the adult borers to deposit their eggs lower on the
trunk. The young borers can be more easily killed by the para-
dichlorobenzene method when they are near the surface of the
ground. Figures 4, 5, 6, and 7 illustrate the steps to be taken in
treating trees with P. D. B.

How MucH PARA-DICHLOROBENZENE SHOULD BE USED?

It is necessary to have a sufficient amount of gas to kill the borers,
regardless of the size of the tree. Experimental work in this state
has shown that three-fourths of an ounce is sufficient for all trees
from two to five years of age. Older trees with large trunks will
require from one to one and one-half ounces. Very small trees may
be treated with one-half of an ounce. A measure holding just the
required amount is convenient for use in the orchard.

WHEN SHOULD PARA-DICHLOROBENZENE BE APPLIED?

Judging from the experimental work in Illinois, the best results
will be obtained when para-dichlorobenzene is applied in fall.
Results from two years’ treatments given from September 20th to
October 25th show from 95% to 100% of the borers killed. From
80% to 90% of the borers were killed by treatments given in late
spring. From our present knowledge, the best time for treating in
southern Illinois—or south of the Vandalia Railroad—is from
September 25th to October 25th; north of this line, from September
20th to October 20th. If the treatment is given in spring, the
material should be applied between May ist and 20th. If it is
applied in summer or very early in fall, the tree may become re-
infested by late-flying moths. If applied too early in spring or too
late in fall the ground is not;warm enough to cause the para-dichloro-
benzene crystals to vaporize,and set free the gas in sufficient amounts
to kill the borers. Soil temperature three inches below the surface
should be at least 60° F. One ‘treatment per year, applied in fall,
should be sufficient. -

Fic. 5. Applying the P. D. B.

Fic. 7. Treated tree; P. D. B. covered with soil.

10

Is THERE ANY DANGER OF KILLING TREES
BY THIS TREATMENT?

Thus far we have not killed any trees in this state where the above
methods were used. Under different soil and weather conditions in
other states trees have been killed. Judging from the results of our
two years of experiments, this material is relatively safe. Further
experiments are necessary before we can be sure of its effects on young
trees. There is a chance that treatments given year after year
may prove injurious, altho this is not likely.

SHOULD PURE PARA-DICHLOROBENZENE BE USED?

Several companies have placed on the market, under trade
names, a mixture of para-dichlorobenzene and other materials. The
para-dichlorobenzene is the only chemical that has been found safe
and effective for killing the peach borer. There is no reason for
paying a high price for materials that are of no value in ridding the
tree of the borers. Only the pure para-dichlorobenzene should be
used.

WHAT DOES IT Cost TO TREAT A TREE WITH
PARA-DICHLOROBENZENE?

At present, para-dichlorobenzene can be obtained for about
30c. to 35c. a pound in small quantities. In large amounts, it can
be obtained for 17c. to 20c.a pound. Allowing 30c. a pound, the cost
for material would be 1%c. a tree where three-fourths of an ounce
was used. A man experienced in this work should be able to treat,
on an average, fifteen to twenty trees an hour. Allowing twelve
an hour, if the wage paid is 30c. an hour, it would cost 2c. a tree
for labor. This is a total cost of 4c. a tree. In worming trees, if a
careful and thoro treatment is given, it is difficult for a man to treat
more than five an hour, which would cost 6c. a tree; and it is generally
advisable to worm in both fall and spring.

ON wHAT AGED TREES SHOULD PARA-DICHLOROBENZENE
BE APPLIED?

Apparently it is safe to use para-dichlorobenzene under. our
conditions on any tree more than one year old. Experiments in
Illinois have not resulted in any injury. Practically all of the trees
treated in 1921 were only one year old. The only reason for not

11

giving this material an unqualified recommendation is that experi-
mental work in the East has shown some injury to young trees.

WHAT EFFECT HAS WET WEATHER ON THE RESULTS
OF TREATMENT WITH THIS MATERIAL?

Illinois experiments on the hill-land orchards seem to show that.
the material is effective, even tho applied the day before or the day
after soaking rains. In the spring of 1920, for example, ten trees
were treated in loess soil at Carbondale on May 15th. It rained
every day for six consecutive days following, 3.97 inches falling from
May 16th to 20th. 77% of the worms found in these trees were
killed. Records for southern Illinois showed eleven other cases
where the material was effective in wet soil.

There is still need of several years’ experimental work before we
can make unqualified recommendations concerning the use of para-
dichlorobenzene. There are a number of points concerning the life
history of the peach borer in this state on which work must be done.
We also need more definite information concerning the effect of the
gas on young trees, and on the cumulative effect of treatments.
Further experiments will be carried on along these lines.

Following, is a partial list of the firms selling para-dichlorobenzene:

Hooker Electro-Chemical Co., 25 Pine St., New York City.
Merck & Co., 45 Park Place, New York City.

Niagara Sprayer Co., Middleport, N. Y.

Interstate Chemical Co., Jersey City, N. J.

Rochester Germicide Co., Rochester, N. Y.

Meyer Bros. Drug Co., St. Louis, Mo.

E. C. Klipstein & Sons Co., 644 Greenwich St., New York City.
International Chemical Co., Cleveland, Ohio.

General Chemical Co., 25 Broad St., New York City.

March 1, 1922.

(64894—10M-2-22)

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UNIVERSITY OF ILLINOIS-URBANA

570IL6C C006
CIRCULAR
1-24

3 0112 017541175