Memorandum of information on insecticides used against Lygus bugs on sugar beets grown for seed

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Material Information

Title:
Memorandum of information on insecticides used against Lygus bugs on sugar beets grown for seed
Physical Description:
4 p. : ; 27 cm.
Language:
English
Creator:
Hills, Orin A., 1903-
United States -- Bureau of Entomology and Plant Quarantine
Publisher:
U.S. Department of Agriculture, Agricultural Research Administration, Bureau of Entomology and Plant Quarantine
Place of Publication:
Washington, D.C
Publication Date:

Subjects

Subjects / Keywords:
Lygus -- Control   ( lcsh )
Sugar beet -- Diseases and pests -- Control   ( lcsh )
Insecticides   ( lcsh )
Genre:
federal government publication   ( marcgt )
non-fiction   ( marcgt )

Notes

General Note:
Caption title.
General Note:
"E-635."
General Note:
"February 1945."
Statement of Responsibility:
by Orin A. Hills.

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 030286894
oclc - 779540092
System ID:
AA00025093:00001

Full Text


February 1945 E-635


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

MEMORAL1DUM OF INFORMATION ON INSECTICIDES USED
AGAINST LYGUS BUGS ON SUGAR BETS GRO'N FCOR SEL

By Orin A. Hills
Division of Truck Crop and Garden Insect Investigations

This memorandum summarizes briefly the results of experiments
conducted during the 1944 season for the control of Igl bugs on sugar beets grown for seed. Several new insecticides were tested on small plots of seed beets and some produced results as good as or better than the pyrethrum extract-sulfur dust previously recommended for the control of Lygqs on this crop. The effect of the Lygus control program on the yield and viability of large and small seed balls has also been further determined, and the purpose of this memorandum is to make the results of these experiments available to those interested in the production of sugar beet seed.

During the 1944 season seven insecticides, five of which had not been previously tested in the field on seed beets, were tet~d in experimental plots. Eight replicate plots, each 24 by 32 feet (annroximately 1/58 acre) were used in each case and the following insecticides were tested: (1) DDT 4.5 percent, pyrophyllite 95.5 percent; (2) a pyrethrum extract dust and sulfur mixture containing 0.20 percent of pyrethrins and 50 percent of sulfur. (This material has given good results in the past and was included in this experiment for comparison with the other insecticides); (3) a dust containing 3.25 percent of beta, beta-dithiocyanodiethyl ether, 75 percent of sulfur, and 21.75 percent of inert ingredients; (4) dinitro-o-cresol 1 percent, sulfur 99 percent; (5) dusting sulfur (325-mesh); (6) a dust containing 20 percent of dry lime-sulfur and 80 percent of dusting sulfur; (7) a dust containing 57 percent of sulfur, 5 percent of petroleum oil, an( 38 percent of talc. The first application was made on May 11, at which time the beets were in the full-bloom stage, and the second anlication was made 8 days later. Insect-nonulatioD samples showed that the one aplication of DDT had reduced Lyrus numbers to a very low l1vel and that they remained so until harvest; a second application was therefore unnecessary. The dinitro-o-cresol caused severe bu-nin- of the plants and one apniication was sufficient to show that this material was not safe for use on seed beets.

The seed from a samnle area four rows wide and 10 feet lone in the center of each plot were harvested, threshed, nnd cleaned, rnl a sample taken from each for germination analysis. A 'No. 7 "2liHoer Mill" and a canvas belt draper were used in the cleaning operation, the seed being run first throu ~h the mill and then over the draper. In milling, as little air as nossible was used to separate the trash




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from the seed, and thus practically all seed were saved. The seed were cleaned over a 7/64-bY 3/1-inch screen and then separated into "large" and [[small" seed by passing them over an 9/641- by 3/Il-inch screen. By this method all seed balls retained by an 9/614- by 3/41-inch screen were termed "large seed" while those seed balls passing through the a/61i- by 3/14-inch screen but retained by the 7/b64- by 3/14-inch screen were termed "'small seed." Thus the "large seed" 'referred to in this memorandum are seed balls over 8/64~ inch in diameter and the "small seed" are those seed balls between 7/ 614 and 8/64 inch in diameter. Yield data and results of germination analyses for large, small, and total seed from the variously treated plots are given in table 1. The analyses of the data in this table showed that there were no significant increases in yield of large. seed due to treatment although there is' a tendency toward an increase in the yield of large seed for those plots treated with DDT. The increase in the yield of small-seed was, however, shown to be mathematically significant for the DDT-treated plots. A definite decrease in yield of large seed is indicated for the plots treated with dinitro-o-cresol, but this decrease is not significant for the small seed.

Results of germination tests in the accompanying table show that
one application of DDT gave results as good as or better than two appli-. cations of the pyrethrum extract-sulfur dust previously recommended for the control of Lgsin seed beets. A few large-scale experiments in
field control were conducted with DDT and similar results were obtained. The plots treated with beta, beta'-dithiocyanodiethvl ether yie lded seed of somewhat better quality than those treated with dusting sulfur, but
there was a tendency toward a decrease in the seed yield from these plots, and further tests are necessary before it an be recommended., The quality of the seed produced on those plots treated with the oil-sulfur and those treated with the mixture of lime-sulfur and sulfur was improved over that from the untreated plots, but these materials were shown to be no better than dusting sulfur alone.

Yield data in the table show that approximately 13 percent of the total yield were small seed which would ordinarily be lost by the use of an 9/6)4- by 3/41-inch screen. It is generally understood that the percent of germinating seed is lower in the case of the small seed.. Past years' data as well as the data in the table substantiate this theory. However, these data also show that where Mgu bugs were controlled the viability of these small seed was improved to an-even greater degree than was the viability of the large seed.

Investigations to date indicate that DDT is a very good insecticide against Lygus on seed beets. Extensive field trials, however have not as yet been made. Experiments of the past season have shown that DDT is very toxic to beneficial insects such as ladybeetles, lacewings, and parasites which occur in the beet fields and which are responsible for holding aphid infestations in check. The action of DDT against aphids is uncertain and therefore the elimination of the insect parasites and predators from the beet fields may create a condition which would result in the rapid buildup of destructive populations of aphids,






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UNIVERSITY OF FLORIDA
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3 1262 09230 3873

DDT now being manufactured is devoted to military uses and only a comparatively small supply is available for experimental use in agriculture. If sufficient DDT becomes available, large-scale commercial field tests are planned for the season of 1945 so that the usefulness of DDT as a control for L s may be properly evaluated and its effect on other insects occurring in the seed beet fields-may be further d.termined.