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with aldrin in 1951 (table 5). This insecticide showed no phytotoxicity 
to cucumbers. 
Allethrin 
When applied directly on the insects in laboratory cage tests in 1950, 
a 0.5-percent allethrin dust proved toxic to third-instar pickleworms, 
but it was less effective against last-instar larvae, even when used at a 
heavy dosage. A 2-percent allethrin dust showed only moderate toxicity 
to last-instar pickleworms. The addition of 1 percent of piperonyl 
cyclonene and of compound 469 did not appreciably increase the toxicity 
of a 0.5-percent allethrin dust. 
In field plots a 1 -percent allethrin dust was of some value against a 
light pickleworm infestation in 1950, but was not of significant value 
when a moderate infestation prevailed in 1951 (table 3). Piperonyl 
butoxide, compound 469, and an activated nicotine did not appreciably 
increase the effectiveness of a 0.5-percent allethrin dust in 1951. 
BHC 
BHC caused serious injury to cucumbers in the spring of 1948 (table 1) 
and was not used in later tests. For tests with gamma BHC, see Lindane. 
Chlordane 
A 2 -percent chlordane dust had no apparent ill effect on cucumbers 
in the spring of 1948 (table 1),, but caused slight to moderate chlorosis 
of about one-third of the plants in the fall of that year. It was one of 
the least effective insecticides against the pickleworm in the fall of 1948 
(table 3). 
Cryolite 
Cryolite gave an intermediate degree of control of the pickleworm. 
It provided adequate protection against the melonworm and cucumber 
beetles, but apparently increased melon aphid populations on cucumbers. 
This aphid was more abundant on cryolite- treated plants than on plants 
receiving any of the other materials in two experiments each in 1948 
and 1949. In 1951 populations of this aphid were highly significantly 
greater on cryolite -treated cucumbers than on untreated plants (table 5). 
A cryolite dust of 50-percent sodium fluoaluminate content gave 
near-adequate control of a moderate pickleworm population when applied 
every 5 or 7 days in 1948, but not when applied every 10 days (table 4). 
Weekly applications in 1949 did not give satisfactory protection against 
a heavy infestation. When accompanied by zineb, a 70-percent cryolite 
