APPLE GROWING IN CALIFORNIA. 85 



control. Its name is derived from the fact that the purplish body 

 of the adult louse is covered with a wool-like, waxy excretion. When 

 once an orchard becomes badly infested it is only with extreme difficulty 

 that this insect may be checked in its ravages. 



The woolly aphis works both above and below ground. The damage 

 to the roots consists in a roughening or knotting of the surface, with 

 the result of more or less decay and destruction of fibrous roots in bad 

 cases. The winter season is spent by the lice both on the branches and 

 trunks above ground and on the roots below the surface. During the 

 summer months a migration is taking place from roots to branches and 

 vice versa, throughout the time of active feeding, with usually a more 

 general migration in the early spring and late fall. One winged gen- 

 t-ration develops during a season, and this in the fall. These winged 

 lice are all viviparous females and give birth to sexual males and 

 females, the latter of which each deposits a single large egg. It is now 

 thought that migration takes place from the apple to the elm, and that 

 the eggs are deposited on the latter, 5 as the eggs cannot be found on the 

 apple trees, though search has been made for them there time and again. 



Control. 



When damaging trees above ground this aphis, like others of its kind, 

 may be readily killed by a spray of Black Leaf "40" and soap, using 

 the former at the strength of one gallon to 1000 gallons of water and 

 about 5 pounds of soap to 100 gallons of water. They are not at all 

 hard to kill with this mixture when it comes in direct contact with their 

 bodies. In order to make it do so a high pressure and a driving spray is 

 necessary. In small orchards we have known this pest to have been kept 

 in check, in the early spring, by the application of coal oil by means of a 

 brush, to colonies located in cracks, knot holes, etc., as they colonized 

 after migrating from the roots. 



rnderground treatment has been on the whole unsatisfactory. In the 

 case of small trees, tobacco dust or a spray of Black Leaf "40" and 

 soap to the bared roots may be quite effective. For larger trees the treat- 

 incut is not practical, as the aphids follow the roots to their extremities, 

 especially if they are shallow. 



Deep rooting of apple trees is desirable, because of the tendency of 

 this pest to attack the shallow roots most severely, as well as for other 

 good reasons. 



Resistant Varieties. 



Some varieties of trees possess more or less resistance to the attack of 

 \\oollv aphis. The Northern Spy probably is more nearty immune than 

 any other variety and for that reason the roots are very often used for 

 propagating purposes. 



Natural Enemies. 



Lacewing flies, syrphid flies, and ladybird beetles frequently keep this 

 pest in check. There is no more effective predaceous enemy in this 

 case than the lacewings, and exceedingly had infestations over large 

 areas have been seen destroyed in a couple of weeks time by them. A 

 little internal parasite, aphelinus mali, is sometimes a considerable factor 

 in its control. 



'See Bui. 217, Maine Exp. Sta. Edith M. Patch. 



