48 MASS. EXPERIMENT STATION BULLETIN 184. 



in other words just before the buds show the least bit of green. This 

 condition would normally be reached during the early part of April in 

 Massachusetts. The term delayed dormant is applied to that period in 

 the development of the cluster buds and foliage when they have ex- 

 panded from a quarter to a half inch. 



It is more or less axiomatic that the hatching of the aphid eggs is about 

 coincident with the first splitting of the apple buds, and that by the 

 time the buds have expanded from a quarter to a half inch, the delaj^ed 

 dormant period, practically all of the eggs have hatched and the young 

 plant hce have migrated to the new growth for food. Observations 

 have confirmed this. Twigs brought in from the field and examined on 

 April 17 had numerous plant lice eggs upon them, but none of these 

 had hatched. The buds were in the late dormant condition. Twigs 

 brought in on April 19 were found to have a few newly hatched individ- 

 uals, which had migrated to those buds just beginning to expand and 

 show the least bit of green available for feeding purposes. From the 

 19th to the 24th of April, newly hatched aphids appeared in increasing 

 numbers. After the latter date only a few new indi\dduals appeared, 

 which could be readily determined by their size. It is evident from this 

 that under favorable weather conditions such as existed during the 

 period mentioned the time of maximum emergence is rather brief. The 

 presence of a few newly hatched individuals on some of the twigs on 

 May 1 indicated that a small number of belated aphids were still hatching 

 from the eggs, but in no case observed had the foliage expanded beyond 

 about half an inch before hatching was completed. No viviparously 

 produced aphids were in evidence at this time. 



Object of Delayed Dormant Spraying. 



In the past the practice of sprajdng with lime-suKur for the control of 

 San Jose scale has been confined for the most part to the dormant or late 

 dormant season. Comparatively recently, however, the practice of de- 

 layed dormant spraying with lime-sulfur has been quite generally advo- 

 cated, based on the assumption that such treatment is fully as effective 

 as dormant or late dormant season applications against the San Jos6 scale, 

 and that apple plant lice in their active stages would offer less resistance 

 to this insecticide than the unhatched eggs. In other words, it is beUeved 

 by some that a delayed application of lime-sulfur at full dormant-season 

 strength, just after the buds have split open and have expanded perhaps 

 not over half an inch, will control the San Jos6 scale, and to quite an 

 extent the apple plant lice as well. Applications at this time, practice 

 has shown, can be made with little or no eventual injury to the foUage. 

 Our tests, so far as the efficiency of the delayed applications of lime- 

 sulfur in controlling plant lice is concerned, have by no means borne out 

 this conclusion. From the standpoint of the fungicidal value of lime- 

 sulfur, delayed dormant applications appear to have some advantage 

 over those of the dormant season. 



