-11- 



with the plants stays there. Plants put in dry lose very little moisture 

 because it can't escape. Even a piece of wet paper toweling or wet sphagnum 

 put in the bag can result in too much moisture followed by decay. 



It is not safe to use polyethylene film thicker than 2 mils because gasses 

 cannot escape rapidly enough. As the plants respire, oxygen is used up, carbon 

 dioJcide increases and the plants smother. 



John S. Bailey 



I I I I I I I I I I I I I I I I 



CHEMICAL THINNING OF APPLES 



At this time (late April) while apples are still in the pre-pink of develop- 

 ment, it looks as though most growers have sufficient Mcintosh bloom for a moderate 

 crop. Naturally, following the heavy crop of last year, this year's bloom is 

 expected to be lighter than a year ago and a smaller crop is anticipated. However, 

 there are occasional blocks or orchards which suffered unusually high losses from 

 frost in 1957, which are going to bloom heavily this spring; and such blocks 

 should be watched closely so that a thinning treatment may be applied if it seems 

 necessary. 



In general, the need for chemical thinning of Mcintosh will probably not be 

 nearly as great as it was a year ago. However, the decision on this point can be 

 delayed until 10 to 14 days after petal-fall. • Probably the most dependable means 

 of determining the need for chemical thinning of Mcintosh 10 to 14 days after bloom 

 is by calculating the number of fruits set per 100 blossoming clusters by actual 

 count on several trees. This means that the number of blossom clusters on at 

 least 2 limbs of 5 to 6 trees must be counted and recorded in each block. Then 

 the number of fruits developing on the same limbs must be determined 10 to 14 

 days after petal-fall. If one finds (by dividing the number of apples by the 

 number of blossom clusters) an average set in excess of 50 to 60 fruits per 100 

 blossoming clusters on trees that have a reasonably heavy bloom, some thinning of 

 Mcintosh may be necessary. A final set of 25 to 35 fruits per 100 blossoming 

 clusters seems to be about right for heavy to moderate blooming Mcintosh. If 50 

 or less fruits are left 10 to 14 days after petal-fall, one may expect reductions 

 in set during the June drop period to be sufficient so that chemical thinning will 

 not be necessary. When in doubt, omit the spray or use '"no more than a weak spray ■^-"^^ " 

 of NAAmide'(25 ppm or 4 oz. of Amid-Thin per 100 gallons of water). We have 

 never seen this treatment seriously overthin Mcintosh. 



Of course, many other varieties may need thinning if they bore little or no 

 crop a year ago. Suggestions concerning such varieties are given in Special 

 Circular No. 189, Chemical Thinning of Apples , which was revised this spring and 

 is now available from your County Agent or from the Mailing Room, University of 

 Massachusetts, Amherst, Massachusetts. 



Following a couple of seasons' work with NAA and NAAmide, with and without 

 additives such as light oil or Tween 20, we have come to the conclusion that the 



