APPLE POWDERY MILDEW. 



13 



crop. Stayman Winesap (Stay man) trees, bearing a heavy crop and 

 situated alongside the Black Ben Davis used in this experiment and 

 sprayed by the orchard owner with iion sulphid (formula 7), showed 

 on this date about 30 per cent of exposed fruit on the south and 

 southwest sides very severely burned. Besides this, defoliation to 

 the extent of 50 per cent in many instances had taken place, and a 

 heavy drop of fruit had been caused. Subsequent observations indi- 

 cated that this variety is particularly subject to injury of this nature. 



Table I. — Results of spraying experiments for the control of apple poivdery 

 mildew at Wenatchee, Wash., in 1915. 



Variety and plat. 



Spray 

 formu- 

 lae 



Dates of ap- 

 plication, b 



Foliage injury, c 



Foliage 



On Apr. 28. 



On June 4. 



On July 29. 



Total. 



fected. 



Black Ben Davis: 



No. 1 



6 



t: 



12a.... 

 11 



5S.... 



Apr. 24, May 



20, June 15, 



July 15. 

 Apr. 24, May 



20, June 15, 



July 15. 

 Apr. 14, 24, 



May 20. 



June 15 



Apr. 24, May 



20. ' 



June 15 



(Apr. 14, 24, 

 1 M a y 20, 

 1 J u n e 15, 

 I July 15. 

 Apr. 14, 24, 



M a y 20, 



J u n e 15, 



July 15. 

 Apr. 24, May 



20, June 15. 

 Not sprayed. 



M a y 20, 



June 15. 



Apr. 24 



May 20, June 



15. 



Apr. 24 



Apr. 24, July 



15. 

 May 20, June 



15. 

 Apr. 24, May 



20, June 15. 



July 15 



Apr. 24, May 



20, June 15. 



July 15 



Apr. 24, May 



20, June 15, 



July 15. 



Per cent. 



Per cent. 



Per cent. 

 2d 



5/ 



Slight in- 

 crease. 



2h 



\ Slight in- 

 / crease. 



...do 



Per ct. 

 2 



6 



} * 



10 



} * 



4 



Per ct. 

 1.4 



No.2 





(«) 



/No i n - 

 \ crease. 



3& 



Uh 



\2* 



2h 



1.5 



No. 3 



U<7 



U<7 



[slight 



...do 



.3 



No. 4 



.3 



No. 5 



.8 



No. 6 



.9 



No.7 



1.1 



No. 8 (check) 











35.1 



Pry or Red: 



No. 9 



r 



|9L.... 

 fl3L... 



r 



r 



[11 L... 



fl2a.... 



|12a L. 



7 



[20; 



1 



fNo i n - 

 \ crease. 



No in- 

 crease. 



} 20 



2.8 



No. 10 



6.5 



No. 11 



1 





2d.. 



1 Slight in- 

 | crease. 



W 



1 



2 



} 2 



16 

 1 



6.1 



No. 12 



1 



1 Slight tip 

 f burning. 



[..do 



[Less than 

 \ 1 p e r 

 | cent. 



f2i 



\5* 



12.6 



No. 13 



14.9 



No. 14 



10.6 



No. 15 (check) 



20.1 

















a For composition of sprays used, see pp. 11-12. 



b Buds in the "pink" (just before full bloom), Apr. 14; petals fallen, calyx not yet closed, Apr. 24; other 

 applications at the time of regular codling-moth sprayings. 

 c Foliage injury expressed in percentage of leaf-surface reduction. 

 d On southwest side of trees. h Increase. 



e Very slight leaf spotting. » Defoliation. 



/ Increase on southwest side of trees. i Defoliation (consisting only of infected leaves). 



g Leaf spotting and margin burning. k Leaf spotting. 



Since climatic factors are known to play such an important part 

 in the development of spray injury, the following data will be of 

 interest in connection with the injury noted. The records of the 



