16 STATION BULLETIN 355 



known and that pooled data are obtained from a homogenous popu- 

 lation. In general the total weight of drops over a series of years 

 will give the most accurate picture for the purpose of comparison. 



EFFECT OF THINNING FRUIT 



In 1939, just after the June drop, 16 trees setting a full crop were 

 paired according to tree diameter and size of top. One of each pair 

 was thinned so that fruits averaged 5 inches apart, the others were 

 left unthinned. 



On the basis of total drops before harvest, some thinned trees 

 dropped about twice as great a proportion of their crop as controls 

 of the same pairs. Of the remainder, the unthinned trees dropped 

 the greater percentage of fruit so that the average difference in per 

 cent of drops between thinned and unthinned trees was not statisti- 

 cally significant. 



BORAX SPRAYS 



Sixteen other trees were selected in the same way as for the thin- 

 ning test, but none of these was thinned. One of each pair was 

 sprayed with 2 pounds of borax i)er 100 gallons of water on July 

 7 and again on July 27 , 1939. Fig. 4 shows that apples held approxi- 

 mately 2 days longer to the trees which had been sprayed with borax 

 than on the unsprayed trees, and by September 22 sprayed trees had 

 dropped only three-fourths as much fruit as the controls. 



Heinicke. ct. al. (7) obtained a great reduction in the preharvest 

 drop of Mcintosh trees susceptible to cork by soil applications of bo- 

 rax in solution in Jul}'. The effect carried over to the following year's 

 crop although there was no visible evidence of cork in the fruit in the 

 second year. The borax applications had no effect on the fruit drop 

 of trees previously free from cork. Batjer and Haller^, on the other 

 hand, found that wdien 20-year-old apple trees growing in a soil low 

 in available boron were fertilized with 1 pound of borax. 3 weeks prior 

 to bloom, the pre-harvest drop was greatly augmented, the per cent 

 drop being nearly quadrupled. 



EFFECT OF SEED NUMBER 



Seed number influences drop and size of fruit. For all trees in 

 both the thinning and borax tests there were, on the average, one to 

 two more seeds in picked fruit than in drops from the same tree. 

 Furthermore, thinned trees showed a definitely smaller difference in 

 seed number between dropped apples and harvested fruit than did 

 unthinned trees (Table 11). There was no significant difference in 

 this respect between borax-sprayed and unsprayed trees (both un- 

 thinned). Apparently more fruits with a smaller number of seeds 

 failed to drop from thinned than from unthinned trees where compe- 

 tition was greater. Thus spraying with borax did not overcome the 

 competition between fruits of different seed number. Whatever ef- 

 fect borax may have had in causing more fruits to remain on the tree, 

 few- and many-seeded apples were affected in like manner. It should 

 be stated that these trees are located on a boron-poor soil and that 



