BULLETIN No. 184. 



DEPARTMENT OF ENTOMOLOGY. 



LATE DORMANT VERSUS DELAYED DOR- 

 MANT OR GREEN TIP TREATMENT FOR 

 THE CONTROL OF APPLE APHIDS. 



BY W. S. REGAN. 



In carrying on field experiments during the summer of 1917 for the 

 control of potato plant lice, commercial Ume-sulfur solution, among 

 other materials, was tested as to its effectiveness. Although this was 

 used at the rate of 1 gallon to 22 gallons of water, about twice the ordinary- 

 summer strength, and in spite of the fact that every precaution was 

 taken to drench thoroughly all parts of the plants, the percentage of 

 plant lice killed was so small, under 10 per cent., that it could in no way 

 be considered of value as an aphidicide at a strength safe to use upon 

 potato foliage. 



Object of Comparative Tests. 



The results of these tests led the writer to question just how effective 

 the usual dormant strength, 1 to 8, of Hme-sulfur would prove against 

 apple aphids when apphed at the delayed dormant period, just after the 

 eggs have hatched. With a view to determining this point, a number of 

 tests have been carried out during the past several weeks. In these 

 experiments commercial lime-sulfur solution was used alone and in com- 

 bination with nicotine sulfate, and several brands of proprietary mis- 

 cible oils were also tried out in comparison. Tests were also made to 

 determine the effect of lime-sulfur and miscible oils upon the unhatched 

 eggs. 



Delayed Dormant Period indicative of Complete Hatching of 



Aphid Eggs. 



Remarks might be prefaced here by the statement that the term 



dormant is taken to mean the condition of the buds in the winter or 



early spring before they begin to swell. By late dormant is meant the 



swollen condition of the buds at the time just before they spht open, or 



