TILE CHEMICAL THI^HIIIIG SITUA TION F OR 1961 



Following a moderate crop of apples on many major varieties in 1960 we 

 can expect a rather heavy bloom in 1961. Certainly, Mcintosh in many orchards 

 appear to have a heavy bloom potential and with favorable weather a heavy set 

 is likely. Most growers now recognize that one of the prime reasons for using 

 a chemical thinner such as Amid-Thin (NA Amide) on Mcintosh is not only to 

 improve the size of persisting fruit but also to help insure annual blossoming 

 of the variety. In fact, this may be the primary reason for chemical thinning 

 this variety since Mcintosh in excess of 2-3/A inches in diameter do not store 

 well and are in less demand than they once were. 



Some of you may wonder whether the standard thinning materials, NAA and 

 NA Amide, have been cleared by the Pure Food and Drug Administration for use 

 this year. Both these materials have been cleared for thinning and labels 

 covering them for this purpose have been printed. The label on Amid-Thin 

 (NA Amide) no longer allows for use of this material in excess of 50 ppm, (1/2 

 lb. per 100 gallons of water) or beyond about 2-1/2 weeks after bloom. In 

 addition, there is no allowance for more than one application of this material. 

 The upper concentration limit for NAA is 20 ppm. (usually 8 ounces per 100 

 gallons of water except for a few double strength formulations where A ounces 

 per 100 gallons would be the limit) as a single spray. In order to comply with 

 these labels we have had to modify our thinning recommendations for some heavy 

 setting varieties. For example, we can no longer recommend two 75 ppm. NA 

 Amide applications for Early Mcintosh and Wealthy at early petal fall and 10 to 

 14 days later. However, there appear to be no regulations preventing an early 

 50 ppm. NA Amide spray followed by a NAA spray 10 to 14 days later if you so 

 desire on these or other varieties. 



Our current recoiranendations concerning both NAA and NA Amide are now 

 available (Chemical Thinning of Apples, Special Circular No. 189, 1961) through 

 your county agent and/or this department in Amherst. 



Some of you may wonder about the possible use of Sevin (1-Naphthyl 

 N-methylcarbamate) as a thinner. Our results obtained in 1960 indicate that it 

 is a very mild thinner at rates of 1 to 2 lbs. per 100 gallons. This material 

 probably won't come close to thinning any heavy setting varieties adequately 

 but it may have a place on such varieties as Mcintosh and Delicious applied 14 

 to 28 days after petal fall. We are not going to recommend the use of 50 per 

 cent wettable Sevin until we have more experience with it and are satisfied that 

 its use will result in suitable "repeat" blossoming as well as adequate thinning. 

 However, if thinning of Delicious or Mcintosh is a problem with you and you are 

 not satisfied with either NAA or NA Amide for this purpose the use of Sevin may 

 be worth a limited trial. The chance of overthinning does not appear to be 

 great with Sevin and it caused no apparent foliage injury at the 1 or 2 pound 

 level in 1960. 



We want to warn those who may wish to use Sevin as an insecticide that it 

 thinned Mcintosh up to at least 30 days after bloom in 1960 and at what point 

 beyond this date it no longer thins Mcintosh does not appear to be certain. In 

 other words, an NA Amide application on Mcintosh at two weeks after petal fall 

 followed by a treatment of Sevin a week later might result in more thinning 

 than desired. We are quite certain Sevin will not thin beyond June drop time, 

 however . 



F. W. Southwick 



