February,’18] HOWARD: INSECTICIDES AND DIABROTICA 
75 
no doubt vary from time to time in their physical characteristics and 
chemical composition the use of kerosene is always uncertain. The re¬ 
sults, however, show that kerosenes of considerable value as insecticides 
and of very slight toxicity to plants can be manufactured. They 
should, however, be manufactured for the particular purpose of insecti¬ 
cides to meet an insecticide test rather than a flash test. 
Summary 
1. Kerosene varies greatly in its physical characteristics and its 
chemical composition, even when coming from the same oil field. 
2. Low boiling point fractions of kerosene are in general more toxic 
to plants than high boiling point fractions when used pure. 
3. Injury by fractions with low boiling points can largely be pre¬ 
vented if they are applied in the form of an emulsion, since the emulsion 
holds the oil away from the plant until such time as it has evaporated. 
4. Emulsification of high boiling point fractions does not give this 
protection since the oil remains on the leaf after the emulsion is de¬ 
stroyed. 
5. Low boiling point fractions are more toxic to insects in the form 
of vapor than high boiling point fractions due to the slight volatility 
of the higher fractions. 
6. High boiling point compounds are more toxic than low boiling 
point compounds when used as contact insecticides in the form of an 
emulsion. 
President R. A. Cooley: I will call for the next paper, “Insecti¬ 
cide Tests with Diabrotica vittata ” by Mr. Howard, of Wisconsin. 
INSECTICIDE TESTS WITH DIABROTICA VITTATA 
By Neale F. Howard, Madison , Wis., Specialist, Bureau of Entomology, 
Truck Crop Insect Investigations 1 
The r61e which insects play in the transmission of certain serious 
plant diseases makes the control of the species involved of even greater 
economic importance than heretofore. During the course of inves¬ 
tigations into the control of insects which transmit cucurbit diseases, 
especially the mosaic disease, the use of stomach poisons received some 
attention. 
A trial was made on a large scale in 1916, at Madison, Wisconsin, 
to control the mosaic disease by controlling the striped cucumber 
1 Published with the permission of the Chief of the Bureau of Entomology. 
