27 



doubtless owing to the addition of the soap in the latter. The differ- 

 ence, however, is very slight, and as foliage will stand a greater strength 

 of the mechanical mixture tlian of the emulsion, as exi)laincd later, 

 this i)oint can not be an objection to the mechanical mixture, as the cost 

 of the additional kerosene is no more than the cost of the soap. In the 

 literature on this subject a strength of from one-fifteentli to one- tenth 

 has generally been recommended for use against various caterpillars and 

 from one-twentieth to one-iifteenth for plant-lice. 1 am inclined to 

 think, however, from tests made this vseason, that tiic strength of the 

 emulsion as thus generally recommended is hardly (Plough to accom- 

 plish the desired results. 



I find that a proportion of two-tenths (two i)arts kerosene to eight 

 parts water) is needed for thorough work with most caterpillars, al- 

 though a proportion of one tenth will kill many young. Thus with 

 Pieris rap(v one-tenth will kill about one-half the larv.e, two-tenths 

 being needed for effectual work. In the case of the catalpa sphinx 

 {Ceratomia catalp(c) one-tenth killed onh^ a few of the newly hatched 

 larva^, while two-tenths killed all. Emulsion killed a larger number 

 of these two species than the mechanical mixture, but still a pro])or- 

 tion of two-tenths was needed for effective work. 



Most species of plant-lice have sliown themselves more tenacious of 

 life than I had formerly supposed, ^yhile the most of them ;ire killed 

 by an application of one-tenth, two-tenths will do more effective work. 

 The principal species experimented with have been the cabbage aphis 

 {Aphis hrassicce) and the grape-vine aphis {Siphonophora viticola). 



With the use of pyrethrum, mixed with either the kerosene or the 

 water, the mixture has somewhat greater strength, the pyrethrum 

 adding just about as much strength to the mixture as the soap in an 

 emulsion. It is easier to use a greater strength of kerosene, however, 

 than it is to add the i)yrethrum. 



Kerosene and Bordeaux mixture go well together, bnt the Bordeaux 

 will not adhere to the foliage as well as when used alone. 1 have used 

 it especially with the grape-vine a})his, which is common in early 

 summer and can be destroyed at the same time that an ai)i)iication of 

 Bordeaux mixture is made. 



The combination of kerosene and Paris green can be made more sue 

 cessfully ])y the use of the kerosene attachment than when Paris green 

 is added to an emulsion. The Paris green, of course, is mixed with the 

 water in the main tank. 



As to the effe(;t of the mechanical mixture on foliage, the results 

 here have been (piite a surprise, for 1 find that the mixture can be ap 

 idied of a much greater strength than can the emulsion. I have api)lied 

 it upon all our common jdants, and repeated the ai)plication at various 

 times to ascertain whether sunlight or other conditions would vary the 

 effect of the a[)plication. I find that all plants will stand one-tenth, 

 and so far as I have experimented only the suntiower and tomato are 



