CERTAIN ELEMENTS IN NURSERY PRACTICE 211 



The nodular swellings or aphis galls are especially common 

 on the roots of nursery stock. The woolly aphis is known to 

 entomologists as Schizoneura lanigera. 



Control. The woolly aphis appears first in summer on the 

 trunk and branches aboveground and it can then be readily 

 controlled by drenching the woolly colonies with 15 per cent 

 kerosene emulsion. The treatment should be made as soon 

 as the aphids appear, and this will prevent many of them from 

 migrating to the roots. 



RED-SPIDER. The minute spider-like, oval-shaped, reddish 

 mites are about -^ inch in length. They are usually found on 

 the underside of the leaves where they live under the pro- 

 tection of a delicate silken web. In 

 feeding, they suck the sap and cause the 

 foliage to turn yellowish in spots. Con- 

 siderable injury may result from the 

 attacks of these mites, especially in the 

 western orchard and nursery sections 

 of Canada and United States. The 

 foliage of peach, prune, plum, apple, 

 cherry, pear, almond, raspberry, rose 

 and many forest trees is attacked. 

 Two species are involved, Tetranychus 

 bimaculatw and the clover mite, Bryobia 

 pratensis. 



Control The clover mite (Fig. 222) 

 lays eggs in autumn on the trunk and 

 branches and the eggs hatch early in 

 the spring. Spraying the hibernating 

 eggs while the trees are dormant with 

 lime-sulfur solution 1 to 9 will prove 

 effective. The red-spider (Tetranychus) hibernates through- 

 out the winter in the ground and crawls back to the foliage in 



FIG. 222. 



The clover 

 ^ 



