18 



CIRCULAR 270, U.S. DEPARTMENT OF AGRICULTURE 



CONTROL 



The method of controlling red spiders, as already stated, depends 

 on the species involved. The overwintering forms of the common 

 red spider sometimes can be reduced by proper cultivation, or by 

 burning the leaves and trash in which they are hibernating. Irri- 

 gation, where practiced, is an important factor in reducing red-spider 

 injury and in facilitating control by spraying. Thrifty, adequately 

 irrigated trees will not suffer nearly so much as those that are 

 dry and in poor condition. This is important, as defoliation is 



always serious if it 

 occurs before Septem- 

 ber. It may force the 

 trees to send out new 

 leaves or blossoms in 

 the fall, materially re- 

 ducing the following 

 year's crop, and it 

 affects the fruit buds 

 and the size of the 

 current year's crop. 

 Spraying is practi- 

 cally the only direct 

 means of control for 

 red spiders. It must 

 be done before July 

 to be of much value. 

 If spraying is delayed 

 until after that time, 

 the mites often be- 

 come so numerous 

 that adequate control 

 is impossible. Dor- 

 mant-season sprays, 

 containing 4 percent 

 of oil emulsion, as 

 used for scale insects 

 or for the leaf roller, 

 are very effective in 

 destroying the over- 

 wintering eggs of the 

 European red mite and the brown mite. The oil should be applied 

 before March 15, if possible, as the trees are sometimes injured 

 by late-dormant oil sprays. Lime-sulphur solution is relatively 

 ineffective against these eggs. Sprays of lime-sulphur solution, how- 

 ever, with 2 or 3 gallons of the concentrate to 100 gallons of water, 

 as used for combating powdery mildew or scab (table l,p. 68), are 

 valuable in destroying the young mites. These sprays should be 

 applied just before the blossoms open and again as a calyx 

 application. 



It is often necessary to use lime-sulphur solution in the dormant- 

 season application on account of the presence of other insects that 

 are best combated with that material. If such insects are on the 

 trees, or if the mites have not been otherwise controlled, a very 

 effective measure consists in using oil in one or more of the summer 



Figure 19.— Overwintering eggs of the European red mite in caly 

 end of apple. Twelve times natural size. 



