ANNUAL REPORT, 1941 93 



A light supplementary application of ammonium sulfate about June 7 was 

 given all the blueberries except those in the manure test. The improved appear- 

 ance of the plants and the increased yield over previous years indicate that this 

 was a good practice. 



Bulletin 358, Blueberry- Culture in Massachusetts, was revised. 



Premature Dropping of Mcintosh Apples. (L. Southwick.) Work on this 

 project largely concerned investigations with "hormone sprays." Some chem- 

 icals such as naphthalene acetic acid and certain of its salts, naphthalene aceta- 

 mide and some others, have been shown to delay natural drop of apples at harvest 

 when applied in dilute spray solutions. These chemicals and several commercial 

 proprietary compounds employing these active ingredients were used in field 

 tests in 1940 and 1941. Bulletin 381, published in February, 1941, summarized 

 the results of experimental work conducted in 1940 and in it the authors at- 

 tempted to evaluate the method of "hormone spraying" especially in relation 

 to Mcintosh. Further tests in 1941 revealed no very different results. There 

 was some evidence that under certain conditions, drop-control sprays on Mcin- 

 tosh were not so effective as in 1940. Many check trees dropped comparatively 

 little this }'ear. In most cases, however, the prehar\est drop from sprayed trees 

 was less than that from check trees in the same block. Some typical percentage 

 drop comparisons, sprayed and unsprayed, follow: 3.7 and 14.5 percent; 12.9 

 and 20.2 percent; 2.3 and 7.5 percent; 10.2 and 13.4 percent; 11.6 and 21.4 per- 

 cent; 7.3 and 18.5 percent; 13.9 and 13.4 percent. It is apparent from these 

 figures that degree of control was not consistent. 



There is some indication that the temperature at the time of application may 

 be important. Possibly fruit growers should wait for temperatures above 60° F. 

 before applying a drop-control spra}-. A more definite statement on this point 

 must await further experiments. 



A limited test with Milton indicated little benefit from spraying. The sprayed 

 trees dropped 31 percent of the total crop compared with 34.6 percent from the 

 check trees. 



Results again demonstrated the desirability of using standard strength sprays 

 with Mcintosh. Weaker sprays were usually less effective. Doubling the 

 standard strength increased the effectiveness of applications. How much im- 

 provement in drop control would be required to offset the increased cost of 

 stronger sprays is problematical and depends on several factors. It can be stated 

 with some assurance, however, that the so-called standard strength of "hormone 

 sprays" should not be reduced with Mcintosh in this State. 



The use of special stickers or summer oil seems to merit some consideration. 

 Theoretically, these materials should tend to improve coverage. Actually, the 

 benefits from their inclusion in hormone sprays have been variable. Usually, 

 drop control has been somewhat better although in some cases improvement has 

 been negligible. It is at least certain that spreaders and stickers are not effective 

 substitutes for good coverage. 



Dusts were tried this year for the first time. These were made up by two com- 

 mercial concerns and were compared with spra}' applications. In about half the 

 tests, dust was only slightly inferior to spray in lessening pre-harvest drop. In 

 the others, dusting was not effective. It is true also that spraying was prac- 

 tically ineffective in some cases. The heavier applications of dusts (4 pounds 

 per tree) seemed more effective than lighter dosages. Until further evidence 

 is at hand, the use of hormone dusts by growers is recommended for trial only. 



