ANNUAL REPORT, 1937 55 



was more leaf burn than usual following the standard spray program and very 

 slight difTerence in visible injury between the modified lime-sulfur programs and 

 the standard. The dry lime-sulfur-sulfur combination caused noticeably more 

 foliage injury, and spray catalizer much less damage than the standard program. 



The season was the most difficult one in recent years in which to attempt to 

 control either disease or insect pests. Unfavorable weather frequently interrupted 

 the spray schedule, especially during the critical period before bloom, and les- 

 sened the efficienc>- of the different applications. The relative merits of the 

 different sprays were based on the results on the variety Mcintosh as follows: 



Percentage of Fruit Showing 

 Material Tested Percentage Injury from — 



of Clean 



Fruit Scab Curculio Codling Spray 



Moth Russet 



Coposil 



throughout season 22.6 56.7 29 8.4 100 



Coposil 



3d and 4th cover sprays.. 69.8 22 6.6 2.8 15.6 

 Copper Zeolite 



3d and 4th cover sprays.. 73.1 8.5 16 3.2 19.5 



Spray catalizer 58.5 20.9 18 3 4.1 



Lime-sulfur modified 57.5 15.7 25.7 4.6 2.1 



Dry lime-sulfur and 325-mesh 



sulfur 42.6 21.6 34.6 7.9 0.6 



Standard program 67 2.4 23.4 6 1.7 



Check 0.0 92.3 35.1 21 0.0 



Sprays to Control White Apple Leaf hopper. The infestation by the second 

 generation of the white apple leafhopper in eastern Massachusetts in 1937 was 

 the most severe in recent years. Examinations of untreated trees in 5 different 

 orchards showed an average of 5 to 20 leafhoppers per leaf during the first week 

 in September. 



Orchard applications of pyrethrum dust 30-70 were generally unsatisfactory. 

 In most cases there was a good knockdown of leafhoppers but a rather rapid 

 recovery and reinfestation. A leaf count in one orchard showed a reduction from 

 8 leafhoppers per leaf to 2, and in several instances a complete cleanup resulted 

 on those branches receiving a direct blast from the duster, but the insects were 

 affected but little where exposed only to dust drift. Applications from the two 

 sides of the tree were more effective than from one side. Favored by hot weather 

 and timely treatments, nicotine-lime dust (2.4 percent nicotine) gave very good 

 control in one orchard and provided excellent protection to the foliage. 



A check on the effectiveness of spray materials applied by the orchardist was 

 very confusing and discouraging, apparently due to an uneven application of the 

 spray. For example, an examination of 100 leaves showed an average of 1.04 

 leafhoppers per leaf, but 60 leaves had 15 hoppers or an average of 0.4 per leaf 

 while the other 40 leaves had 89 hoppers or 2.2 per leaf. In another case, 100 

 leaves averaged 0.55 per leaf where 60 leaves had no hoppers and 40 leaves had 

 55 hoppers. 



Under these conditions, counts indicated a good reduction in leafhoppers from 

 nicotine and pyrethrum materials used with soap. When counts were made 5 and 

 8 days after spraying, it appeared that the number of hoppers decreased with time 

 where nicotine was used, but that the number of hoppers increased with time where 

 pyrethrum was used. 



In laboratory experiments with pyrethrum and cube dust and with pyrethrum 



