ORCHARD INSECTS OF THE PACIFIC NORTHWEST 



47 



afforded. There are several generations. Winged adults develop 

 in the middle of the summer and migrate to water cress, peppergrass, 

 and other plants of the mustard family. A later generation returns to 

 the cherry in the fall and pro- 

 duces wingless individuals that 

 lay the overwintering eggs. 



CONTROL 



Spraying after the leaves are 

 curled is of little use, but very 

 good control may be obtained by 

 spraying just as the buds are 

 breaking. Nicotine sulfate (40 

 percent nicotine) may be used in 

 the proportion of three-fourths of 

 a pint to 100 gallons of water, 

 with soap or casein spreader, or 

 added to dormant sprays of lime- 

 sulfur or oil. 



Red Spiders 



On cherry trees the web- 

 spinning mites ( Tetranychus pad- 

 Jicus McG. and T. willamettei 

 McG.) are usually more injurious 

 than other species of red spiders. 

 They hibernate beneath the fallen 

 leaves or in other trash and 

 migrate into the trees in the 

 spring as soon as the new leaves have appeared. They are not often 

 seen before June and do their most serious injury after the fruit has 

 been picked. Cherry trees are frequently neglected at this time and 

 allowed to become dry; this condition aggravates the injury caused 

 by the mites and may very materially reduce the succeeding year's 

 crop by weakening the fruit buds. If cherry trees have a dry and 

 dusty appearance late in the summer, it may be suspected that mites 

 are on the trees. Closer examination will reveal the webbing, in which 

 the small greenish or yellowish mites are running about. More 

 complete descriptions of these and other red spiders will be found on 

 page 16. 



CONTROL 



Since no stage of the web-spinning mites is on the trees during the 

 winter, dormant-season sprays are of no value in their control. In the 

 coastal valleys, where control of the brown rot is often necessary, the 

 sulfur sprays used for this purpose should also be adequate for 

 keeping the mites in check. Otherwise it is better to delay the spray- 

 ing until after the fruit has been picked and then to spray the trees 

 very thoroughly with \){ gallons of oil emulsion, or with 2 gallons of 

 lime-sulfur solution, or 3 to 5 pounds of colloidal sulfur, to 100 gal- 

 lons of water. If the brown mite is present, it may be controlled 



Figure 



55. — Injury to cherry foliar 

 the black cherry aphid. 



