5- 
were diluted with sulfur than when used undiluted or mixed with hydrated 
lime or copper-lime. 
In general, the early studies indicated that (1) the pickleworm is 
more difficult to control than the melonworm, (2) pickleworm mortality 
counts are impractical after the insects begin tunneling into the plants 
and fruits, (3) for adequate control the pickleworm must be killed before 
this tunneling begins, (4) undusted barrier rows and check plots serve 
as sources of infestation of surrounding plants, and (5) more effective 
control measures and insecticides involving residues less hazardous 
than used previously are needed. 
PHYTOTOXICITY EXPERIMENTS 
The effect of the periodic use of several new insecticides on the 
growth of three varieties of cucumbers was determined in the experi- 
ments conducted in the spring of 1948 and 1949. Practically no insects 
were present on cucumbers during these experiments, and all yield 
differences are considered to be due to the direct effect of the insecti- 
cides on the plants. 
Each plot consisted of two rows 6 feet wide and 36.3 feet long. The 
plots were arranged in randomized blocks. Seven applications were 
made at weekly intervals in 1948 and eight in 1949, beginning about a 
week after the plants came up (when the second true leaves appeared) 
and ending the day of the third harvesting in 1948, and that of the first 
harvesting in 1949. The applications were made in the morning with 
rotary hand machines on wet to moist plants, with one or two trips per 
row. Dry plants were sprayed with water before being dusted. A cloth- 
covered hood with a plastic-cloth apron 8 or 10 feet long was often used 
to reduce insecticide drift. 
In 1948 from 8 to 19 pounds per acre were used in the first four 
dustings and from 20 to 37 pounds thereafter. In 1949 the dosage ranged 
from 12 to 20 pounds for the first five dustings and from 20 to 26 pounds 
thereafter. Nine harvestings at 2- to 3-day intervals were made each 
season. 
The yields of marketable cucumbers obtained during these experi- 
ments are summarized in table 1. 
In 1948 a BHC dust severely bleached and stunted the plants of each 
variety from the outset, and reduced the yield of the Marketer variety 
by 35 percent and that of S. C. 5 (a mildew-resistant breeding line) by 
69 percent. 
In 1949 an impregnated 1 -percent DDT dust made from a commercial 
dust that was stated to contain 10 percent of purified DDT (setting point 
103° C.) and 23 percent of an aromatic petroleum -derivative solvent 
significantly affected cucumber yields. It caused chlorosis and stunting 
of the plants from the outset, the injury being severe after the third 
