- f) 



Table 2. Tlie influence i of chemical thinning on fruit set and size of 

 "Return" and "On" blooming Early Mcintosh trees. 1964 



19611 

 Treatments 



1 



Applied' 



"Return" Bloom Trees 



1. Check 



2. Sevin-1#(50% W.P.) PF 



■ NAD -50 ppm. PF+13 



3. NAD-50 ppm. - PF 



M. Sevin-1#(50% W.P.) PF 



NAA-20 ppm. PF+13 



5. NAA-20 ppm. PF+13 



6. NAD-50 ppm. PF+13 

 "On" Bloom Trees 



7. Sevin-1#(50% W.P.) PF 

 NAA-20 ppm. ' PF+13 



Fruits per cm. 



of limb 

 circumference 



19.2a+ 



S.Ocd 

 13.9b 



8.8c 



9.5c 



14.2b 



Avg. fruit 

 diajneter 

 (inches) 



2.01a 



2.15cd 

 2.ipbc 



2.2Ue 

 2.17d 

 2.07ab 



5.7d 



2.34f 



Five trees per treatment. 



^PF=Petal-fall; PF+13=13 days after petal-fall. 



3 

 Fruit size measurements made August 7, 196I+, (35 fruits at random per 



tree) about 2 weeks before harvest commenced. 



Means followed by different letters are significantly different at the 

 5% level. 



From these data, it is evident that, when a relatively heavy "return" 

 bloom is obtained on a heavy setting variety such as Early Mcintosh, 

 chemical thinning needs to be continued at essentially the same rate as 

 for "on" trees. In fact, these data indicate that the "on" trees are 

 easier to thin than the "return" blooming trees. Failure of fruit to 

 size as well on the "return" blooming trees, even when well thinned, 

 may be related to the two dry summers of 1963 and 1964, or to this fac- 

 tor plus the influence of two successive heavy crops on a normally bien- 

 nial variety. The exhaustive effects of annual cropping may tend to re- 

 duce tree (including root) growth; consequently, the rate of fruit growth 

 is less than that which occurs on trees bearing similar crops in alter- 



