52 MASS. EXPERIMENT STATION BULLETIN 339 



lead arsenate throughout the season; a section received lead arsenate through 

 the 1st cover spray and basic zinc arsenate thereafter, and in the third section 

 basic zinc arsenate was used throughout the season. Both arsenicals were used 

 at the same dosage and with the same fungicides. The relative effectiveness 

 of these materials on Mcintosh was as follows: 



Percentage of fruit showing injury from — 



Percentage of 



Material clean fruit Curculio Codling Moth Scab 



Basic zinc arsenate 70.8 0.6 3.1 20.2 



Lead arsenate and basic zinc 



arsenate 84.2 0.8 2.5 10.8 



Lead arsenate 84 1.2 0.9 13 



On the basis of one season's tests the results secured in insect control from 

 basic zinc arsenate were very promising, especially when that material was used 

 in the late summer sprays following lead arsenate in earlier applications. 

 Since these are the critical sprays from the spray residue standpoint, the 

 efficiency of zinc arsenate is significant. No injury to fruit or foliage was noted 

 following the application of either material. 



Apple Maggot Control. (A. I. Bourne and W. D. Whitcomb.) The 

 appearance and relative abundance of the adult flies were approximately 

 normal. Observations throughout the State indicated that in well-sprayed 

 orchards and with accurate timing of sprays the insect caused little damage. 

 The abnormal conditions, consequent upon severe winter injury and wholesale 

 removal of border orchards, were much less apparent in 1936 than during the 

 two previous seasons. The problem offered by neglected trees adjoining well- 

 cared-for orchards confronted many growers and appears to be the chief limiting 

 factor in the control of this pest in commercial orchards. 



The record of emergence of apple maggot flies under different conditions of 

 soil and exposure, made by Professor Whitcomb at Waltham, is as follows: 



Date of Emergence of Apple Maggot Flies, Waltham 



In Sun In Shade 



Cultivated 



1st fly June 30 



25% flies July 12 



50% flies July 14 



75% flies July 25 



1st fly 



25% flies 

 50% flies 

 75% flies 



The number of flies emerging equalled 30.76 percent of the total and was the 

 smallest since the experiment was started. Dry soil in May and July and a 

 generally low vitality of the maggots developing in the fall of 1935 contributed 



