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Analysea of pea pods and kernels from plots treated with DDT Indi- 
cated the presence of DDT on the pods, but its absence on the kernels* 
The amount of DDT present on the pods was proportional to the percent- 
age of DDT used,— Lange (241 ) . 
Eight applications of 5 percent DDT in light summer spray oil — 
average about -J- gallon per acre— were made to ■various vegetables (^ acre) 
by hand atomizer from June 6 to August 1. The kale was fed to chickens 
from June throughout the summer and all the vegetables were oonsumed by 
the family and others, with no ill effects. The DDT residue on the 
beans (Blue Lake) at the time they were canned was 0.029 grain per pound. 
No other residue analysis was made. --Gray (168) . 
DDT residue on fruits, vegetables, alfalfa, and olive foliage and 
fruit was determined by extracting with benzene and dehydrochlorinating 
with alcoholic sodium hydroxide. Alfalfa treated twice with 3-percent 
DDT dust at the rate of 28 pounds per acre-application bore a DDT resi- 
due of 29 p.p.m. (fresh weight). Bartlett pears sprayed with 5 pounds 
of A-20 per 100 gallons of water bore DDT residues of 0.5 to 3.7 p.p.m. 
On pears sprayed with 2% quarts of SH-20 per 100 gallons of water the 
DDT residues ranged from 1.7 to 6.1 p.p.m. The DDT residues on some 
products were as follows : On walnuts, 13 and 43 micrograms per square 
inoh of surface after 1 and 2 sprays containing 5 pounds of 20-percent 
wettable DDT powder per 100 gallons of wateri on small green tomatoes 
8 p.p.m., and on ripe tomatoes, average weight 50 grams, not over 0.5 
p.p«m. after 4 sprays containing 5 pounds of 20-percent wettable DDT 
powder plus 6 ounces of blood albumin per 100 gallons of water. 
Weathering of DDT residues 
Field tests conducted during the past summer have indicated that 
DDT deposits on plants do not have the residual aotion anticipated as 
a result of tests on household insects. Deposits have been reported 
effective over a period of months in indoor tests, but under outdoor 
conditions they generally have remained effective for not more than 14 
to 18 days. This was found to be the oase in certain tests with the 
Japanese beetle on linden trees, with cabbage caterpillars on cabbage, 
and with the codling moth on apple. Apparently some factors in the 
outdoor environment decompose the DDT or remove it from the foliage. 
Moisture and sunlight are generally considered the two most important 
factors in outdoor weathering, but it is possible that heat may be a 
factor on the upper surface of foliage. Tests to determine the action 
of sunlight on the toxicity of DDT residues were not successful be- 
cause of extensive periods of cloudy weather. After a few preliminary 
trials it seemed more practical to expose sprayed glass plates to an 
ultraviolet lamp so that different exposure periods could be used. It 
was recognized, of course, that this type of radiation is only a frac- 
tion of the spectrum of sunlight, but it was felt that some preliminary 
information of value might be obtained. The ultraviolet source was a 
