Influence of temperature on the effectiveness of DDT, and the comparative toxicity of DDT and lead arsenate to larvae of...

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Material Information

Title:
Influence of temperature on the effectiveness of DDT, and the comparative toxicity of DDT and lead arsenate to larvae of the Japanese beetle in soil
Physical Description:
6, 5 p. : ill. ; 27 cm.
Language:
English
Creator:
Fleming, Walter E ( Walter Ernest ), 1899-
Maines, Warren W., 1911-
United States -- Bureau of Entomology and Plant Quarantine
Publisher:
U.S. Dept. of Agriculture, Agricultural Research Administration, Bureau of Entomology and Plant Quarantine
Place of Publication:
Washington, D.C.
Publication Date:

Subjects

Subjects / Keywords:
Japanese beetle -- Larvae -- Control   ( lcsh )
Soil pesticides   ( lcsh )
DDT (Insecticide)   ( lcsh )
Lead arsenate   ( lcsh )
Soils -- Effect of temperature on   ( lcsh )
Genre:
federal government publication   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )

Notes

Bibliography:
Includes bibliographical references (p. 5).
Statement of Responsibility:
by Walter E. Fleming and Warren W. Maines.
General Note:
Caption title.
General Note:
"E-624."
General Note:
"September 1944."

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 030289052
oclc - 779845866
System ID:
AA00025105:00001

Full Text

LIBRARY
PLANT BOARD

September 1944 E-624

United States Department of Agriculture
Agricultural Research Administration
Bureau of Entomology and Plant Quarantine



INFLUENCE OF TEMPERATURE ON THE EFFECTIVENESS OF DDT,
AND THE COMPARATIVE TOXICITY OF DDT AND LEAD ARSENAL
TO LARVAE OF THE JAPANESE BEETLE IN SOIL

By Walter E. Fleming and Warren W. Marines,
Division of Fruit Insect Investigations


INTRODUCTION

Preliminary tests during the summer of 1943 showed that DDT
(2,2-bis(p-chlorophenyl)-l,l,l-trichloroethane) was very effective
against larvae of the Japanese beetle (Popillia Japonica Newman).
In the fall an investigation was undertaken to establish the rela-
tionship between the temperature of the soil and the insecticidal
action of DDT, and to compare the toxicity of this material with
that of lead arsenate.

THE DDOT

The DT used in this investigation was the pure material. In
order to facilitate mixing the material with soil, it was diluted
with talc in the ratio of 1:9 by weight. This mixture was suffi-
ciently fine to pass through a 100-mesh screen.

EFFECTIVENESS OF DDT AT DIFFERENT TEMPERATURES

The DDT was thoroughly mixed with sifted sassafras sandy loam
at the rates of 0.416, 1.04, and 2.08 grams per cubic foot, which
was equivalent to incorporating 10, 25, and 50 pounds of DDT with
the upper 3 inches of an acre of soil. The soil and the chemical
were mixed by being passed twice through a gyratory riddle. The
soil was then placed in trays that were 18 inches square and
3-3/4 inches deep, about 1/3 cubic foot of soil being put into each
tray. The soil was brought to optimum moisture, and grass seed was
sown. Each experimental unit consisted of two or more trays of
unpoisoned soil and two or more trays of each treatment with DDT.

Experimental units were placed in chambers, in which tempera-
ture was maintained with a variation of 10 at 50, 60, 70, and
80 F. A few days after an experimental unit had been placed in a
chamber, 100 third instars were introduced into each treated and







- 2 -


untreated soil. The different batches of third instars, which varied
in age -nmd degree of development, were collected in the field. At inter-
vals which varied with the temperature the larvae were removed from the
soil for examination. A record was made of the number of dead and living
individuals in each tray. After examination the living larvae were
returned to the soil and each tray was reseeded and watered. The experi-
ments were repeated from four to tTwemlve times with different batches of
larvae, a total of 10,400 being used in this investigation.

The mortality of larvae in soil containing DDT is the result of
poisoning and, to some extent, other factors such as bacterial disease,
nematodes, and injury. In order to estimate the net mortality that
could be attributed to poisoning, the percentage of the larvae killed
by each treatment was determined by the formula:

Number alive in Number alive in
Percent killed by poison untreated soil treated soil 100
percent killed by poison Number alive in untreated soil 00

Scatter diagrams of the relationship between the percentage killed
and the number of days the larvae had been in the treated soil were
prepared for the 10-, 25-, and 50-pourd treatments at each temperature.
The average time-mortality curves wei-e then calculated from these data.
These curves are presented in figure 1.

The deviation of each experimental value from the curve was deter-
mined. From these deviations, the average standard deviation of the
10-pound treatment was found to be 26.8 percent, of the 25-pound treat-
ment 21.5 percent, and of the 50-pound treatment 18.3 percent. The
individual experimental values were not entered in figure 1 because the
number of then (862) tended to be confusing on the preliminary charts.

The experimental errors are somewhat higher than usually obtained
in this type of work but may be attributed to the variability in the
resistance of the different batches of larvae to poisoning and to the
difficulty of incorporating such small quantities of a poison uniformly
throughout a mass of soil. The tallest quantity of lead arsenate
recommended for soil treatment against the Japanese beetle is 500, pounds
per acre, or 1 part of lead arsenate to 1,600 parts of 9cil by weight.
The DDT w.,s i-aixod with soil at tLc& rats of 1:16,000, 31:32,,.), -d
1:80,000.

As can be seen from figurE 1, tL.. ef'ectiveLe:s of bj. .- .wst tLc
third instars was modified profouacly by the temperatLura. The lu-poaud
treatment required on the average something over 90 days at 50 F. to
kill half of the larvae, 26.9 days at 60 F., 23.5 days at 70 F., and
11.7 days at 80 F. The 25-pound treatment accomplished this in 35.6
days at 50 F., in 19.5 days at 60 F., in 11.3 days at 70 F., and in
9.1 days at 80 F., and the 50-pound treatment in 26.5 days at 50 F.
in 14.5 days at 60 F., in 10.2 days at 70 F., and in 6.3 days at 806 F.








3 -


RELATIVE VELOCITY OF POISONING AT DIFFERENT TfERATURES

There seemed to be a definite relationship between the tempera-
ture and the velocity of poisoning with a given treatment of DDTo
As the reciprocals of the time required to obtain a definite level
of mortality are a convenient measure of the relative velocity of
poisoning, the data were converted to this form for further study.

From the average curves given in figure 1 the number of days
required to kill 30, 40, 50, 60, and 70 percent of the larvae were
determined, then the reciprocals of these values were obtained.
For each level of poisoning the reciprocals were plotted against
the corresponding temperatures. An approximate straight-line re-
lationship seemed to exist between the relative velocity of poisoning
and the temperature. The slopes of these lines were determined by
the method of least squares. The curves for the 30-, 50-, and
70-percent levels of poisoning are presented in figure 2. The
curves for the 40- and 60-percent levels were omitted because of
the lack of space.

The velocity of poisoning increased progressively with the
increment in the temperature. At 60 1. the velocity of poisoning
was u ally double that at 50 F.; at 70 P. it was tripled, and
at 80 F. it was quadrupled. The velocity of poisoning with lead
arsenate has been found to increase with temperature in the same
manner(2) ./

TBR]SHOLD TMF NATURE OF POISONING

The minimum temperature at which larvae are sufficiently active
to ingest DT in the soil is an important factor in that it limits
the period of insecticoidal action in the fall and in the spring. The
threshold temperature above which the larvae begin to ingest per-
ceptible amounts of food has not been determined experimentally.

It may not be possible to determine experimentally the tempera-
ture above which poisoning will be perceptible but it is possible to
obtain from the reciprocal curves given in figure 2 an empirical
estimate of this temperature. When the curves for the 25- and the
50-pound treatments of DDT were extended below 50 F. they inter-
sected the X axis at points between 39.3 and 43.6 F. A temperature
of 40 F. has been accepted tentatively as the approximate threshold
of poisoning of larvae by IDT. These results are similar to those
obtained with lead arsenate.



i/ Underscored numbers in parentheses refer to Literature Cited, p. 6.






-4-


POISONING AND THEMAL SUMMATION

With 40 F. as the threshold, it was found with the 10-, 25-, and
50-poLund treatments that the products of the number of days and the num-
ber of degrees above the threshold were practically constant values for
each level of poisoning. It was evident that the rate of poisoning was
closely correlated with the suirmnation of the day-degree units above the
threshold.

The mortalities obtained with the 10-, 25-, and 50-pound treatments
at temperatures of 50, 60, 70, and 80 F. were plotted against the
summations of the day-degree units above the empirical threshold. The
scatter diagrams showing this relationship are presented in figure 3.
The average curves were then calculated and the average standard devia-
tions were determined. The average standard deviations are indicated
on the charts as broken lines above and below each curve.

The standard errors of the thermal unit-mortality curves for the
25- and the 50-pound treatments were practically the same as those of
the time-mortality curves for these treatments. The standard error for
the 10-pound treatment was slightly larger.

This study of the data tends to demonstrate that, as with Jead
arsenate, the level of mortality obtained with a treatment of DrT is
dependent upon the number of day-degree units accumulated after the
larvae came into contact with the poison. With these data, it is pos-
sible to estimate the possible effectiveness of the 10-, 25-, and the
50-pound treatments from a summation of the thermal units following the
application of the treatment.

DDT VS LEAD ARSENATE

Lead arsenate has been used for the control of larvae of the Japanese
beetle in soil for many years. It is of great interest therefore to
compare the relative effectiveness of lead arsenate and DDT in poisoning.
the larvae.

A study was made of the relative velocities of poisoning of the
larvae by DDT and lead arsenate. The reciprocals of the time raqulred
to poison '.\lf of the larvae with 500 and 1,000 pounds of loal ,i v:-;uote
and with 10, 25, and 50 pounds of DDT were plotted against the 7:.' sjoL- -
ing temperatures. These curves are shown in figure 4. In t'ls U-.: thr
height of each curve above the X axis was adjusted slightly so .- all
of the intercepts would be at 40 F.

It was found that the velocity of poisoning with the 500-pound lead
arseirate treatment was half the rate with the 1,000-pound tro +'r.-'-
The velocity of poisoning with 10 pounds of DDT per acre was not sig
nificantly different from the rate with 1,000 pounds of lead arsanateo








-5-


The rates with the 25- and the 50-pound treatments of DDT were sig-
nificantly greater than that of 1,000 pounds of lead arsenate. The
velocity of poisoning with the 25-pound treatment was 28 percent
faster and the velocity with the 50-pound treatment 76 percent faster
than the rate with 1,000 pounds of lead arsenate.

The poisoning of larvae in the soil is a joint function of the
amount of poison in the soil and the accumulated thermal units. The
joint functional relation with the 10-, 25-, and 50-pound treatments
of DDT was determined according to the procedure outlined by Ezekiel (1).
The joint functional relation for the lead arsenate treatments has
been determined previously (2). The average mortalities obtained
with the 10-, 25-, and 50-pound treatments of DDT and with the 200-,
500-, and 1,000-pound treatments of lead arsenate with thermal units
from 100 to 1,000 are presented in figure 5.

The 200-pound treatment of lead arsenate was relatively ineffec-
tive, the mortality not reaching 20 percent with 1,000 day-degree
units. With the 500-pound arsenical treatment, a mortality in
excess of 50 percent was obtained with 800 thermal units. This
level of mortality was obtained with the 1,000-pound arsenical
treatment with 500 thermal units. With DDT a mortality of 50 per-
cent or greater was obtained with the 10-pound treatment and 500
thermal units and with the 25-pound treatment and 400 thermal units.
The mortality with the 50-pound treatment approached 50 percent
with 300 thermal units. Within this range of thermal units none
of the lead arsenate treatments poisoned more than 90 percent of
the larvae. Mortalities in excess of 95 percent were obtained with
the 25- and the 50-pound treatments of DDT.

The molecular weight of lead arsenate is 347.17; that of DDT
is 354.35. As 10 pounds of DDT is very close in effectiveness to
1,000 pounds of lead arsenate in sassafras sandy loam, it is
evident that, pound for pound, or molecule for molecule, DDT is
about 100 times as toxic to the larvae as is lead arsenate.

SUMMARY

An investigation was carried on to establish the iLfluence of
temperature on the effectiveness of DDT against third instars of
the Japanese beetle and to compare the relative toxicities of DDT
and lead arsenate in the soil.

The velocity of poisoning of the larvae with DDT increased
progressively with the increment in the temperature. At 60 F.
the velocity was double that at 50 F., it was tripled at 70 F.,
and quadrupled at 80 F. The velocity of poisoning with lead
arsenate has been found to increase in the same manner.








-6-


The empirical threshold of poisoning appeared to be about 40 F.,
as with lead arsenate. There was found to be a close correlation between
the poisoning of the larvae and the summation of the day-thermal units
above this threshold.

The velocity of poisoning with DDT at the rate of 10 pounds per
acre was not significantly different from the rate with 1,000 pounds of
lead arsenate. The velocity with the 25-pound treatment was 28 percent
faster and with the 50-pound treatment 76 percent faster than that with
1,000 pounds of lead arsenate.

Pound for pound, or molecule for molecule, DDT appears to be 100
times as toxic to the larvae in the soil as is lead arsenate.

LIT SR.TURE CITED

(1) Ezekiel, M.
1930. Methods of correlation analysis. 427 pp. New York.

(2) Fleming, W. E., and W. W. Marines
Influence of temperature on effectiveness of lead
arsenate against larvae of the Japanese beetle in
the soil. U. S. Dept. Agr., Bur. Ent. and Plant
Quar. E-622.





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7. /0 POUNDS PER ACRE

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DAY5 AFTER INTRODUCTION OF LARVAE

Figure 1. -- Effectiveness of the 10-, 25-, and 50-pound treatLents with
DDT against third-instar larvae at constant temperatures from 50 to
800 F.





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Figure 2. -- Rqelative velocity of po:isoninR of th~ird-:instar larvae w-ith
t~he 10-, 25-, and 50-pound. treatments of DDT at temperatur-es of 500,
600, 700, and 800 F., and the empirical threshold of poisoning.
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units above the empirical threshold.


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Figure 4. -- Relative velocity of poisoning of third-instar larvae with
DDT and lead arsenate.


























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