ORCHARD INSECTS OF THE PACIFIC NORTHWEST 



27 



Control of the woolly aphid in cankers caused by the perennial 

 canker is not always accomplished by the usual sprays. The Oregon 

 Agricultural Experiment Station has recommended trimming out all 

 cankered bark early in the sum- 

 mer, allowing the wounds to heal 

 10 to 14 days, and then applying 

 (with a brush or a paint gun) a 

 mixture of 1 part of nicotine 

 sulfate (40 percent nicotine) and 

 6 parts of tree paint. The 

 wounds should be repainted an- 

 nually. Information about tree 

 paint may be secured from the 

 Oregon Agricultural Experiment 

 Station. 



Control of the aphids on the 

 roots is extremely difficult. The 

 most practical method is to 

 keep the trees in a thrifty, vigor- 

 ous condition, by means of prop- 

 er cultivation and fertilization, 

 so that they can withstand the 

 drain caused by these insects. 

 Applications of tobacco refuse 

 about the roots, fumigation with 

 carbon disulfide, and other reme- 

 dial treatments have been tried, 

 but are not always successful. 

 Paradichlorobenzene, recom- 

 mended for controlling the peach 

 borer, has been used with some 

 success for the woolly aphid, par- 

 ticularly on old trees. It should 

 be applied in the same manner 

 as for the peach borer (p. 55), at 

 any time during the summer or 

 fall, at the rate of % to 1 ounce 

 per tree. 



Treehoppers 



Young orchards containing al- 

 falfa or clover cover crops are 

 subject to the attacks of several 

 species of treehoppers, among 



which the buffalo treehopper ^ on A , , . , , 



, ri i77 /T7>\\ .li Figure 30. — Apple twig scarred by green 



(Ceresa bubalus (F.)), the green clover treehoppers in laying eggs. X 3. 



clover treehopper (Stictocephala 



inermis (F.)), and the dark-colored treehopper (C. basalis Walk.) 



(fig. 29) are the most injurious. The injury is caused by the wounds 



and scars made by the female in laying her eggs in the bark of the 



trees (fig. 30). These scars are cut by the female with her ovipositor, 



and may be roughened and ragged or clean-cut, longitudinal slits, 



depending on the species making them. The injury rarely extends 



