ORCHARD INSECTS OF THE PACIFIC NORTHWEST 



19 



The brown mite or clover mite (Bryobia praetiosa Koch) (fig. 20) 

 also passes the winter in the egg stage, the eggs being very similar to 

 those of the European red mite and not distinguishable from them 

 with the naked eye. They hatch at about the same time in the 

 spring, and the habits and life history of the two species are much 

 alike. The brown mites spin no webbing and usually congregate in 

 roughened places on the twigs 

 and branches during the da}', 

 migrating to the leaves at 

 night to feed. This habit of 

 feeding at night and the lack 

 of webbing make them rather 

 inconspicuous, and their pres- 

 ence is usually first noted be- 

 cause of the whitening of the 

 leaves caused by their feed- 

 ing. The adult mites are 

 dull reddish or greenish, and 

 are flatter and have longer 

 legs than the European red 

 mites. They are found on 

 deciduous fruit trees and on 

 clover and other forage crops. 



CONTROL 



The method of controlling 

 red spiders, as already stated , 

 depends on the species in- 

 volved. The overwintering 

 forms of the Pacific mite 

 sometimes can be reduced by 

 proper cultivation, or by 

 burning the leaves and trash 

 in which they are hibernat- 

 ing. Irrigation, where prac- 

 ticed, 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 September. It may 

 force the trees to send out new leaves or blossoms in the fall, materially 

 reducing the following year's crop, and it affects the fruit buds and 

 the size of the current year's crop. 



Spraying is practically 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 become so numerous 

 that adequate control is impossible. Dormant-season sprays, contain- 

 ing 4 percent of oil emulsion, as used for scale insects or for the leaf 

 roller, are very effective in destroying the overwintering 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-sulfur solution is relatively ineffective 

 against these eggs. Sprays of lime-sulfur solution, however, with 

 2 or 3 gallons of the concentrate to 100 gallons of water, as used for 



Figure 20. — Adult clover mite. X 45. 



