Tests of DDT and pyrethrum in oil solutions and in emulsions against the earworm in sweet corn


Material Information

Tests of DDT and pyrethrum in oil solutions and in emulsions against the earworm in sweet corn
Physical Description:
7 p. : ; 27 cm.
Blanchard, R. A
Satterthwait, A. F
United States -- Bureau of Entomology and Plant Quarantine
U.S. Dept. of Agriculture, Agricultural Research Administration, Bureau of Entomology and Plant Quarantine
Place of Publication:
Washington, D.C
Publication Date:


Subjects / Keywords:
DDT (Insecticide) -- Testing   ( lcsh )
Pyrethrum (Insecticide) -- Testing   ( lcsh )
Helicoverpa armigera -- Control   ( lcsh )


Additional Physical Form:
Also available in electronic format.
General Note:
Caption title.
General Note:
General Note:
"July 1945."
Statement of Responsibility:
by R.A. Blanchard and A.F. Satterthwait.

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 030290258
oclc - 779856137
System ID:

Full Text

July 1945 a-665
United States Depatxmen of r; u Agricultutial Research Admid retion Bureau of Entomology and Plant Qarantine


By R. A. Blimbhard and A. i. Satterthwait, Division of Cereal and Forage Insect Investigations

Market gardeneri in the important sweet-corn-growing sections of Illinois have not favorably considered the application of oil
insecticides by the hand-injection method for control of the corn earworm (Heliothis armiger (Hbn.)). J h ore, this method is
too expensive for use on canning corn ~erefore, in 1943 preliminary tests were conducted. with oil-water lions containing
pyrethrum, in an effort to find a cheaper minxture that could be
rapidly and effectively applied to the ea externally as an atomized spray. These tests did not give a high depee of control, apparently because of the poor physical characteristic~ of the emulsions. In an
effort to improve them, further tests with pyrethrum (0.2 percent
pyrethrins) or technical DDT (1-trich3or,2-bis(p-chlorophenyl)ethane),
in oil solution and in emulsions, were c oki. in 194114 in corn
planted for canning or for market at Gibvon City and Collinsville, Ill.
The solutions and the emulsions were applied both by injection and
atomi nation.
Experimental Met! ho

The emulsions were mixed by hand in small quantities. This method of mixing is laborious and inefficient, but out of a large
number of trials seven satisfactory fast-breaking emulsions and eight
stable emulsionsi were obtained.

Injections were made with a small hand injector manufactured for the purpose, at the rate of 0.6 mi. per ear regardless of the type of material. The insecticide was atomized with a small paint spray gun,
pressure being supplied from a cylinder of carbon dioxide. The oil
solutions and fast-breaking emulsions were atomized at 30 to 35
pounds pressure, and the heavier stable e~lions at 40 .to 45 pounds.
Enough material was applied to wet the silks and upper parts of the
ears with little or no run-off.

SThe term "stable emulsion" is used in this paper to refer to mixtures that did not separate noticeably. In one instance, at least, a mixture that appeared to be stable when stirred with a glass rod was
relatively fast-breaking when made later with an electric mixer.

rI4VL 2 6 1945


From 25 to 50 ears were treated with each material in each test. The treatments were applied to some ears before the silks had wilted and to others immediately afterward. The results were determined when the corn reached the marketing stage.


Table 1 shows the data on control of the earworm with the
different materials when applied by atomization and by injectiono The number of ears daaged represents those having more than lj-inch tip injury. Comparative amounts of injury to tips of the ears, as indicated by prevention of kernel development, are shown in table 2 for three series of tests conducted at one location. DDT residues resulting from the application of the insecticide In an oil solution, a fast-breaking emulsion, and a stable emulsion were determined by the Division of Insecticide Investigations and are given in table 3.


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Table 3.--DDT residues resulting from injection and atomization of 2
percent of DDT in oil solution and in emulsions

Method of Husked ears Husk plus silk
Formulation -app~lication j
Chlorine IDDT Chlorine DT

-g 2--r ear MS. per ear
Oil solution Atomized 0-095 0.27

Formula 69 Injected .1146 8 0.0134 0.1341
Formula 71B Injected .336 2.78 .195 1.905
Atomized .090 .22 .771 7.71

Check (untreated) .056 0 not run

quantities of DDT probably are slightly high since they were
determined from the organic chlorine content of the samples
uncorrected for chlorine in nontreated material*

As shorn in table 1, DDT in mineral oil or in an emulsion gave
much better control than did pyrethrum. DDT in one emulsion which did not contain oil was somewhat more efficient when injected, or with two applications atomized, than pyrethrum in straight mineral oil. Althog the plots were subjected to showers of rain from 2 to 9 days after the materials were applied, good control was obtained by atomization of several of the oil emulsions containing DDT, whereas none of the emulsions containing pyrethr-um offered any promise. It cannot be considered* however, that the best type of emulsion or best possible method of application has yet been employed.
A part of the damage in the ears treated by atomization with DDT apparently resulted from reinfestation by the corn earworm, since most of the larvae observed in the ears at harvest were small* An undetermined amount of the damage in one test was due to the fall armwworm (LapkYgma frugiperda (A. and S.)). This armworm and larger earworms entering through the sides of the husks appeared to cause more injury to ears treated by injection than to those treated by atomization. Considering the above points, DDT in an emulsion or oil solution applied by atomization seems very promising for control of the earworm. These tests were preliminary in character, however, and no recommendations for practical farm use can yet be made. Further information is needed on the best mixtures to use, on their toxicity to the plants, on the quantities of DDT residue present on the portions of the plants actually eaten by man or animals, and on the toxicity hazard of these residues.


All but one of 'the formulations containing either DDT or prretbruzi caused some reduction in development of tip kernels when applied by injection. The tip-kernel lose was much less when the mixtures were applied by atomization. although on an occasionally ear the damage was relatively severe. The loss due to U.ok of tip development in the sar's treated with emulsions applied by atomization was not appreciably greater than the loss in untreated ears. Neither did the emulsionis appear to affect kernel development in the ears having fresh silks at the time of application any more than they did ears with wilted silks. In addition to preventing complete development of the ear tips, injection of these emulsions caused slight to severe rotting of the ears. Then atomized onto the ear tips, only one of the emulsions caused any rotting of the ears',
Slight yellowing occurred on plants atomized with M)T and pyretbrm both in straight oil and in emulsions. In most cases this was not, thought to affect development of the ears in any way. The most severe burning was found in those plots atomized with emulsions containing th. solvents xylene and cyclohexanone. hmulsifier Amine 220 may have contributed to the damage. The plot that received a double treatment of the emulsion containing xylene as a solvent and Triton B3-1956 as the emulsifier was very severely burned, Excessive amounts of straight oil &culating behind leaf sheaths or points of attachment of the ears caused burning at the points of contact* Neither DDT nor pyrethrum of Itself seemed to damage the plants.

UNIVERSITY OF FLORIDA 3 1262 09238 7454