26 \\M \l. REPORTS Of DEPARTMENT OF ACHK'l'LTURE. 1944 
DDT. [n addition, 2 materials thai had been developed elsewhere and 
were submitted for testing were found to be more toxic to houseflies 
than pyrethrum. 
TESTS 1 1 F si BSTTTUTE MATERIALS CONTINUED 
The search for noncritical insecticide materials for use on food 
plant- was continued. In preliminary tests on 130 samples of new 
materials, 14 synthetics showed toxicity to 2 or more species of leaf- 
feeding insects. Of the plant materials tested, preparations con- 
taining ext racts of yam bean and sabadilla seed exhibited considerable 
toxicity to Leaf-feeding larvae. 
In tests <'f powdered -odium fluoride for relative killing power 
aga insl the American cockroach, a sample approximately 30 microns in 
average particle size killed 50 percent, a 10-microp sample 65 percent, 
and a 5-micron sample 75 percent. One new material has been tested 
thai equals or exceeds -odium fluoride in toxicity to these roaches. 
In cooperative work with the Eastern Regional Research Labors 
lory of the Bureau of Agricultural and Industrial Chemistry on bet- 
ter utilization of nicotine as an insecticide. 244 new samples were 
tested on plant-feeding insects. Most of these samples (220) were 
preparations containing nicotine compounds pin- a material intended 
to act as a synergist. Seven of the materials added to the nicotine 
dust increased the effectiveness of the preparation against 2 species 
of plant pests. 
In cooperative tests five samples of four species of rotenone-bearin<: 
loots from Puerto Rico were tested for insecticidal action. A strik- 
ing difference in the toxicity of extractives other than rotenone was 
found. 
NEW FUMIGATION SCHEDULES DFYF.LOPFD 
Wartime shipping regulations and conditions prevent the fumi<:a 
iiou of carlots <>l vegetables to conform to Japanese beetle quarantine 
regulations, prior i<> icing for shipment. New dosage schedules for 
methyl bromide were therefore developed that permit treatment under 
various condition- of precooling and icing, under which procedure 
produce c:m be shipped without delay. 
Further research in vacuum Fumigation of nursery stock for elimi 
nation of white-fringed beetle larvae has shown that the previously 
approved dosage schedules can be substantially reduced, with conse- 
quent material reduction in the danger of Injury to certain types of 
plant*?. Additional treatment schedules have been developed, and 
these now cover the temperature range of 40* to 80° S\ 
SMOKE AEROSOLS snow PROMIS1 MSAINST AGRN I LTURA1 PESTS 
The production of insecticidal aerosols by means of heat rather 
than by liquefied L r a> is being studied to determine their usefulness 
against agricultural pests. Preliminary field tests against gypsy 
moth larvae showed a high mortality several hundred feet from the 
generator, 
INSECTICIDE INVESTIG HIONS 
Chemical investigations relating to insecticides and fungicides were 
concerned largely with the development and improvement of insects 
