this concentration are remote. 



Assume now that you have a block of Mcintosh on 

 M.26 that require only 150 gal/acre for a dilute spray. 

 If you put the same 30 g a.i. in the tank with 150 gal- 

 lons of water you will end up with a concentration of 

 53 ppm. Adequate thinning of easy-to-thin cultivars 

 with Accel alone is possible at this concentration. Fol- 

 lowing this procedure, orchardists will be able to deter- 

 mine if they are able to obtain adequate results by fol- 

 lowing label directions. 



Double Applications 



The label allows two applications of Accel with 30 

 g a.i. for each application. Research results on Mcin- 

 tosh for two years suggest that two applications are no 

 better than one for thinning. However, return bloom 

 was significantly increased with two applications of 

 Accel in 1993. 



Time of Application 



Application of Accel at petal fall is not as effective 

 as application at the 10 mm stage. More effective thin- 

 ning and larger fruit size is achieved when Accel is ap- 

 plied at the later date, when cell division is proceeding 

 at maximum rate and developing fruit are more suscep- 

 tible to chemical thinners. 



orchardists apply Accel at any time between the 6- and 

 1 2-mm stage of fruit development when favorably warm 

 temperatures are predicted for at least three days. 



Combination Sprays with Either 

 NAA or Sevin 



The most effective thinning treatments have been 

 those in which chemical thinners have been combined. 

 Accel and Sevin have proved to be a very good combi- 

 nation. Accel and NAA have proved to be a very poor 

 combination on Delicious and Fuji. We have combined 

 Accel and NAA on Mcintosh and have achieved very 

 good results. Some growers have reported that NAA 

 and Accel worked well on Mcintosh in 1994. Proceed 

 with caution with this combination, especially when try- 

 ing it for the first time on different cultivars, in particu- 

 lar if they have shown a tendency to form pygmy fruit. 



There is some reluctance to use Sevin in the thin- 

 ning program because of the potential to kill mite preda- 

 tors, about which there is a lack of consensus even 

 among experts. The specific predators present in the 

 orchard and the degree of resistance to Sevin by preda- 

 tors must be determined. 



Cost of Application 



Accel is the most expensive chemical thinner in 



Temperature 



All chemical thinners are 

 more effective when applied at 

 high temperatures. This maybe 

 particularly true of Accel. Or- 

 chardist cannot change the 

 weather; however, it may be pos- 

 sible to select a period of time 

 when temperatures are warm and 

 the chances of getting thinning 

 with Accel are improved. Disap- 

 pointing thinning can be expected 

 if temperatures at and following 

 application are in the 60's. Ac- 

 ceptable results can be expected 

 when temperatures are in the mid 

 to upper 70's and good results 

 often occur when temperatures 

 rise into the 80's. 



Therefore, we suggest that 



Table 5. Estimated cost/acre of applying Accel, Sevin, and NAA 

 alone and in combination to Mcintosh apple trees (dilute gallonage 

 requirement of 150 gal/acre) with one or two applications. 



* Accel 20 g in 35.6 oz = $50.85. 



** Fruitone N 1.25 lb container = $26.54. 



*** Sevin XLR 1 gal = $24.20. I pt XLR = 1 lb Sevin 50WP. 



Fruit Notes, Spring, 1995 



