Dusting as an alternative to spraying has been included in stop-drop 

 experiments and often is as effective as spraying. Dusting is effective 

 only when there is enough nnoisture on foliage to make a deposit stick. 



SPRAY SOLUTIONS AND THEIR USE 



Much has been learned about advantageous use of successful stop-drop 

 chemicals. Following are present practices and principles, based on ad- 

 vances in research: 



Suiting Chemical and Dilution to Use 



Success with stop-drop spraying calls for selection of a suitable 

 chemical and in the weakest solution that will be effective. The weakest 

 solution that gives stop-drop control is the most advantageous on several 

 important counts: It is economical. It is less likely to cause side effects, 

 such as overripening and softening of fruit, or damage to buds and foliage. 

 An over -strong solution can make fruit hard to pick. 



NAA can be used on any of the commercial varieties of apples and 

 pears. 



For apples, an NAA stop-drop ground spray is generally kept to a 

 standard strength of 10 p. p.m. (parts per million). 



For pears, an NAA ground spray containing 5 p. p.m. is adequate. 

 Stronger solutions may cause overripening. 



2,4-D is useful only for Winesap and Stayman apples and Bartlett 

 pears. 



To avoid tree injury, concentrations of Z,4-D should be kept at 5 to 7 

 p. p.m. for Winesap and Stayman apples--never more than 7; for Bartlett 

 pears, usually 2 to 3 p. p.m. --never more than 5. 



2,4,5-T and Z,4,5-TP can be used on any of the commercial varieties 

 of apples, but should not be used on pears. 



A rate of 20 p. p.m. is considered the maximum strength of 2,4,5-T 

 and 2,4,5-TP that can be used without causing apples to ripen and soften 

 undesirably. For some varieties, weaker solutions have proved adequate -- 

 for exannple: 10 p. p.m. for Delicious and Winesap; 15 p. p.m. for Golden 

 Delicious, Stayman, and York. For Rome, 20 p. p.m. are needed. 



Quantity 



Quantity of any solution applied should be sufficient to cover trees 

 thoroughly and evenly. In early research it was supposed that spray must 

 contact fruit stems in order to be carried to the stem-spur junction. Later 

 work, however, has shown that foliage is the main transmission route. 



To spray an acre of large trees from the ground with any of the dilute 

 fruit- sticking solutions requires from 600 to 1,000 gallons. 



