ANNUAL REPORT, 1937 59 



that there was no opportunity to study the effects of contact sprays upon either 

 the insects or the plants. 



There was no evidence of the fungus disease of thrips which for several years 

 was very effective in reducing the numbers of the insects. By the time this disease 

 would have normally appeared, there were few, if any, onion plants which had 

 not succumbed to blast 



The Spray Residue Problem. (A. I. Bourne.) Although no further reductions 

 in the limit of tolerance on lead residues were made for the shipping season of 

 1937, growers found the problem of residue prevention complicated by weather 

 conditions. 



During the early season the spray program was often interrupted by frequent 

 rains, and proper timing of applications was practically impossible. Scab control 

 proved to be especially difficult and necessitated the use of emergency sprays. 

 Considerable burning of foliage and russeting of fruit resulted from the frequent 

 heavy spraying to control this disease. 



Work of previous seasons has shown that unless weather conditions are very 

 favorable, any spray after the 2d cover spray might build up excessive residue. 

 The emergency scab spray of late June increased this danger. The rainfall between 

 this emergency spray and the 3d cover spray and between the 3d and 4th cover 

 sprays was not sufficient to allow the normal removal of the residue. These 

 successive applications, therefore, built up formidable amounts of spra^,- deposit 

 which the three heavy storms of August removed partially but not sufficiently to 

 eliminate the danger of excessive residue. As a result in many orchards the fruit 

 showed excessive amounts of residue at harvest. 



A study was made of phenothiazine as a possible substitute for lead arsenate. 

 Both these materials were used in the 4 cover sprays in a block which had received 

 the standard spray program up to that time. The same wettable sulfur fungicide 

 was used with both materials. No spray injury to foliage or fruit followed the 

 use of either material. The difference in control of insect pests between the two 

 materials was slight but in all cases in favor of lead arsenate as shown in the 

 following table. 



Percentage of Fruit Showing Injury from — 



Curculio Codling Moth Minor Insects 



20.1 4.1 3 



17.8 2.9 1.1 



The chief drawbacks to the use of phenothiazine in its present form appear to 

 be inferior suspension qualities and lack of adhesiveness. 



The codling moth problem is the one which in most cases leads the fruit grower 

 into difficulties from excessive spray residue on harvested fruit. In Massachu- 

 setts much of the damage is due to late season "stings" or shallow pits caused 

 by young 2d brood larvae in August and September. Arsenical sprays at that 

 season build up an excess of spray residue, and to remove it involves the washing 

 of fruit; contact sprays require frequent applications and are e.xpensive. 



A study was made of possible measures to supplement the present spray pro- 

 gram, and of these the use of chemically treated codling moth bands seemed the 

 most promising. These were used in an orchard where it was estimated that 

 -from 75 to 80 percent of the 1936 crop showed codling moth damage. The bands 

 were placed on the trees about June 15 and were examined October 21, after the 

 crop was harvested. In late spring, in preparation for banding, the trunks and 

 main branches of the trees in the test blocks were thoroughly scraped to remove 

 loose bark. At that time many of the trees yielded 80 or more overwintering 

 codling moth larvae. When the bands were examined in the fall, a total of 4,078 



