TREATMENT FOR CONTROL OF APPLE APHIDS. 49 



On the other hand it has been recognized by some that only by the 

 addition of nicotine sulfate to the lime-sulfur solution, when this is ap- 

 plied as a delayed dormant spray, can the aphids be satisfactorily con- 

 trolled. This would indicate that the nicotine sulfate is mainly respon- 

 sible for the control of the plant lice, and that the only reason for delaying 

 the lime-sulfur treatment and combining it with nicotine sulfate is to 

 make necessary only one application instead of two. Then, too, some 

 advocate the addition of an arsenical to the above combination, at the 

 delayed dormant period, for the control of bud moth, case bearers, etc., 

 making possible, theoretically at least, by this insecticide combination 

 the control of San Jos6 scale, apple aphids and certain foliage feeders by 

 one application. 



Comparative Tests for the Destruction of Aphid Eggs under 

 Laboratory Conditions. 



The first tests were made for the purpose of determining the com- 

 parative efficiency of lime-sulfur solution and miscible oils against the 

 unhatched aphid eggs. The lime-sulfur was a fresh sample of a com- 

 mercial concentrate, having a density of 34° Beaum^. This was used at 

 the strength recommended upon the container for dormant appUcations, 

 1 to 8. Two proprietary miscible oils were tested, these being diluted 

 1 to 15, the usual dormant-season strength. Although both samples 

 were fresh from the manufacturers, one was evidently imperfect as there 

 was some free oil present. In the tests, however, this imperfect sample 

 showed to less advantage in destrojdng the eggs than the well-prepared 

 sample, a rather unexpected outcome, perhaps, in view of the presence 

 of free oil. These tests, as in the case of those following in which the aim 

 was to determine the comparative killing efficiency, were carried out in 

 the laboratory, where careful counts could be made and results checked. 

 Dipping the infested apple twigs was resorted to rather than spraj'ing, 

 in order to insure uniformity of treatment, as by the latter method any 

 variability of application might lead to an improper interpretation. On 

 examination, shortly after the infested twigs were brought in from the 

 field, it was impossible to make any estimate of the probable number of 

 eggs that would hatch, since a large percentage of the eggs were apparently 

 dead from some cause, as indicated by their shriveled condition. Twigs 

 of as nearly the same size and degree of infestation as possible were se- 

 lected for insecticide treatment and check, the average length of the 

 twigs being about 8 inches. No definite percentage of efficiency can be 

 given for the tests against the eggs. The results should be taken as 

 merely comparative and in the way of a generaUzation, and are perhaps 

 in need of further verification both in the laboratory and under field con- 

 ditions. The tests against the unhatched eggs were begun when the 

 buds were in the late dormant condition and at such a short time before 

 hatching occurred that it was impossible to carry out verification checks. 

 The results are given in the following table : — 



