ENTOMOLOGY AND PLANT QUARANTINE 
33 
Paradichlorobeiizene is used as a soil fiimigaiit in combating Japanese beetle 
grubs in nursery stock, and for its effective use the concentration in the 
treated soil must be watched. No method for its estimation was available, but 
one was worked out which appears quite satisfactory for use with soils con- 
taining water, peat, leafmold, or cow manure. 
CHEMICAL INVESTIGATIONS ON OILS AND OIL EMULSIONS 
The principal objective of this project was the comparison of the insecticidal 
value of certain vegetable oils, namely, peanut, corn, cottonseed, pine, and 
orange oils, with a commonly used petroleum oil. In tests against mealybugs 
it was found that the first three were about as good as petroleum oil, and under 
some conditions might be better, as for instance when used at large dosages. 
In tests of the same oils against overwintering eggs of the scurfy scale, it was 
found that the drying property of each oil was an important index of the 
toxicity, quick drying resulting in lesser etiicacy. In the study of the effect 
of adding toxicants to the oils, it was found that nicotine and nicotine-beta- 
naphthol improved notably the action of petroleum oil, but did not similarly 
aid corn oil. Pine oil and orange oil were found to be poor because tliey 
volatilized too rapidly to be effective insecticides and were quite active in 
injuring the plants. Of all the Additional toxicants tried, the nicotine and 
betanaphthol combination seemed particularly worthy of further study. 
This project was discontinued near the end of the year, and the personnel 
transferred to Beltsville for work on the development of stickers. 
CHEMICAL INVESTIGATIONS ON ACCESSORY MATERIALS FOR USE WITH 
INSECTICIDES 
An extensive investigation of the wetting and spreading properties of mix- 
tures of various fatty acids with sodium hydroxide and with sodium carbonate 
was carried on, in order to better understand the action of soaps, which are 
so often used as emulsifiers in oil emulsions and as welters and spreaders for 
other spray materials. It was demonstrated that the surface activity increases 
fairly regularly with increase in molecular weight of the fatty acid, thus 
following the properties of foaming and detergency. The spreading power of 
solutions made with sodium hydroxide was found to be (luite sensitive to 
changes in the acid base ratio, whereas solutions preijared from sodium car- 
bonate were not, indicating the possibility of stabilizing the action of soaps 
by the use of the carbonate. 
A special study was made of triethanolamine oleate. because of its recent 
popularity in published spray recommendations. It was found to be a generally 
effective wetting agent. A somewhat similar study was made of solutions of 
trimethyl benzylammonium oleate, which has recently become commercially 
available, and it was found to resemble closely sodium oleate. 
A study was made of welters and adhesives for use with phenothiazine, 
nicotine-peat, and derris. 
TESTS TO DETERMINE TOXICITY OF NEW INSECTICIDAL COMPOUNDS, USING 
GOLDFISH 
The principal work of this project was directed toward the finding of possible 
relationships between toxicity and chemical constitution, as an aid to the 
project of developing synthetic organic insecticides. To this end the three 
isomeric tolyl mercaptans or thibcresols were thoroughly studied. When com- 
pared at the points of minimum product of time and concentration, the orthi^ 
isomer was found to be 1.19 and the para isomer 2.19 times as toxic as the 
meta compound, these relationships being practically the same as found pre- 
viously for the corresponding cresols. The mercaptans are from four to eight 
times as toxic as phenol, but only one-fortieth to one eighty-fifth as toxic as 
rotenone. The replacement of the oxygen atom of the cresol molecule with 
sulphur therefore results in a fourfold increase in toxicity, as compared with 
a sevenfold increase in changing from phenol to thioi)henol. 
A study similar to the above was begun with the nitro phenols. Preliminary 
results show the para isomer to be decidedly more toxic than the ortho com- 
pound, as was the case with both the cresols and the thiocresols. 
