and is now available. Our suggestions for the chemical thinning of apples with 

 Naphthalene acetic acid (NAA) or Naphthalene acetamide (NA Amide) are essentially 

 the same as they have been for the past few years. The principal' precaution that 

 has been added is that these materials should not be used shortly after low 

 temperature injury has occurred to the foliage even though no apparent Injury to 

 flowers or young fruit has taken place. Low temperature injury to the foliage 

 may occur at temperatures of 28-30° F and below, resulting in some crinkling of 

 the young spur leaves. Eventually this tissue will heal but for at least four 

 or five days after this injury has occurred the usual application of NAA or 

 NA Amide (Amid-Thin) may greatly increase the amount of thinning and leaf injury 

 obtained. We observed this phenomenan in one block last year and now suspect that 

 this is probably the reason for occasional isolated cases of foliage injury from 

 NA Amide . 



Last year we found (with Golden Delicious) that an application of NAA about 

 two weeks after petal fall results in a temporary slowing do\-m of the rate of 

 growth of persisting fruit. This influence lasts about 10 days. In other words, 

 these thinners appear to have a temporary growth inhibiting action on non-shedding 

 fruit and for a time the average size of persisting fruit on chemically thinned 

 trees may be smaller than similar fruit on unthinned trees. This temporary re- 

 pressive action of NAA may result in a loss of approximately 1/8 of an inch in 

 diameter growth. However, it may be expected, because of the ultimate increase 

 in the leaf to fruit ration following the use of thinners that the size of fruit 

 from thinned trees will eventually surpass that of fruits on comparable heavily 

 set, unthinned trees. Also, the benefits of these sprays in improving the degree 

 of flowering of many apple varieties the following year still makes the use of 

 these materials desirable in years when oversetting occurs. 



There is another material, which appears to be a post-bloom apple thinner. 

 The material is the insecticide, Sevin. Reports in quite a few areas indicate 

 that Sevin may reduce the set and total yield when applied anytime from peta- 

 fall up to 25 to 30 days after bloom. It is our suggestion that you avoid the 

 use of Sevin during this period until more complete knowledge of its thinning in- 

 fluence is gained. We plan to conduct several experiments with Sevin to determine 

 what its thinning capacity is in comparison to the NAA type materials. Until there 

 is information of this sort with our varieties, Sevin should not be considered for 

 thinning purposes. 



F. W. Southwick 



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



Dr. Lord on Sick Leave 



During the extended absence of our able Extension Pomologist the rest of 

 the Pomology Staff will attempt to handle urgent Extension requests. Dr. Lord 

 is recovering satisfactorily from his operation at the Farren Memorial Hospital 

 in Montague City. However, several x^^eeks of recuperation at his home in 

 Sunderland will be necessary before he will be back on the job of serving you 

 fruit growers. 



A. P. French 



