78 



The high degree of effectiveness exhibited by Black-leaf "40" at the above 

 dilutions is undoubtedlj^ due to its ovicidal action, since, as shown in Tables VI 

 and VII, eggs were found in the plots treated with these materials in great excess 

 of the numbers of larvae found later in the same plots. Substantiation of these 

 observations has been sought bv laboratory tests. 



In these tests Black-leaf "40" at the strengths of 1-100 and 1-250 killed all the 

 eggs which were not parasitized. It is interesting to observe that Black-leaf "40" 

 does not destroy the egg parasites. Parasitized eggs included in the experiments 

 yielded the adult wasps even when sprayed with the greatest strength of Black- 

 leaf "40". 



Recommendations. — The experiments here recorded indicate that almost com- 

 plete relief from squash vine borer attack can be gained by four appUcations in 

 July of Black-leaf "40" at a strength of 1 part in 100 parts of water, where the 

 applications are made ^\^th a power sprayer. At the same strength, the material 

 is over 90 per cent effective applied with a low-pressure, small-capacity outfit such 

 as the compressed air sprayer. Applied at a strength of 1 part in 250 parts of 

 water with the aid of a power sprayer, the material is also over 90 per cent effective. 

 Lead arsenate gives too small a percentage of control to warrant its use. 



On the basis of the experimental evidence, the follomng recommendations are 

 made for the use of nicotine sulfate against the squash vine borer. 



1. If a compressed air sprayer, knapsack pump, or other smaU capacity, low-pres- 

 sure outfit is to be used, apply Black-leaf "40" at the rate of 1 part in 100 parts of 

 water (1..3 fluid ounces per gallon) making 4 applications, one week apart in Jul.y. 



2. If a machine capable of maintaining a pressure of 100 to 150 pounds per square^ 

 inch is to be used, such as a good barrel pump or a power outfit, apply Black-leaf "40" 

 at the rate of 1 part in 250 parts of water (3.2 pints in 100 gallons), making 4 applica- 

 tions, one week apart in July. 



3. In spraying, be sure to drench all sides of the stem at the base. See that the 

 leaf-stalks, and the under and upper surfaces of the leaves are thoroughly sprayed. 

 When the plants have started to run, it is hardly necessary to spray the runners beyond 

 three or four feet from the center of the hill. 



4. Thorough spraying will largely free the sprayed fields from borers. Extermina- 

 tion may then be made complete by an examination of the plants in mid-August, 

 cutting out those borers that have escaped the spray. 



Spraying may be begun during the first week in July. It would be better, however,, 

 to examine a few plants closely every day during the last week in June, in order 

 to discover the first eggs. The first spray should be applied not later than a week 

 after eggs are discovered. 



Cost of Treatments Versus expected Profits. 



Nicotine sulfate is a i-elativcly expensive insecticide, and any spraying operation 

 using this iiiatorial at a strengtli of one ])art in one hundred parts of water, or one 

 part in two hundred fift\' parts of water, is a costly treatment, which will be quite 

 likely to prove impractical under certain conditions of squash culture {i.e., where 

 the squash vine borer is not a serious pest). 



The expense of treatment can be materially reduced by following the suggestions- 

 given below. 



