-11 - 
Residues at harvest after the use of DDT on cucumbers are discussed 
on page 17. 
Dieldrin 
In laboratory cage tests in 1950 a 2.5-percent dieldrin dust gave 
complete kill of third-instar pickleworms, but only 30-percent kill of 
last instars. In a field experiment this dust gave complete control of 
a light pickleworm infestation in 1950 and adequate control of a moderate 
infestation in 1951, being among the most effective materials and as 
toxic as a 1 -percent lindane dust (table 3). Dieldrin gave excellent 
control of the melon aphid in 1951 (table 5). It showed no phytotoxicity 
to cucumbers in 1950 and 1951. 
A 1 -percent endrin (the stereoisomer of dieldrin) dust was as effec- 
tive against the pickleworm and the melon aphid as a 2.5-percent dieldrin 
dust in 1951 (tables 3 and 5). Endrin caused slight to moderate burning 
and chlorosis of cucumber foliage. 
Heptachlor 
A 0.24-percent heptachlor spray (2 pounds of a 50-percent wettable 
powder to 50 gallons) gave good control of a light pickleworm infesta- 
tion in 1950, but a 2.5-percent dust did not prove very effective against 
a moderate infestation in 1951 (table 3), The dust apparently gave 
partial protection against the melon aphid (table 5). Heptachlor showed 
no phytotoxicity to cucumbers. 
Lindane (or gamma BHC) 
Lindane (or gamma BHC) was the most generally effective of the 
insecticides given extensive trials on cucumbers and squash. Good to 
excellent control of the pickleworm, as well as of the banded, spotted, 
and striped cucumber beetles, the melonworm, and the melon aphid, 
was obtained when a 1 -percent dust of either material was applied 
every 7 to 10 days at about 20 pounds per acre (tables 3, 4, and 5). 
Emulsion sprays containing 0.025 to 0.058 percent of lindane applied 
to give 0.125 to 0.250 pound of lindane per acre and a suspension spray 
containing 0.06 percent applied at the rate of 0.25 pound of lindane per 
acre also gave good control of these insects. In 1950 and 1951 weekly 
applications of a 0.5-percent lindane dust gave good control of the pickle- 
worm when accompanied by separate approximately weekly applications 
of zineb. 
Gamma BHC and lindane provided satisfactory insect control on 
several thousand acres of fall-crop cucumbers grown in the vicinity of 
Charleston, S. C, between 1948 and 1951. 
STATE 
