Some Important Orchard Plant Lici-: 13 



In summing up the meager knowledge at hand relative to the 

 effect of climatic conditions on the abundance of plant lice, we 

 may say that a late cool spring is likely to show a serious attack 

 of these insects, while an earl}- warm one is likely to show^ few of 

 them. On the other hand, it is quite possible that a late cool 

 spring might not be accompanied l:)y a plant louse outjjreak be- 

 cause of the destructive effect of a late low temperature, or the 

 activity of lady-bird beetles, or still other agencies less well 

 understood. 



It is also quite possible that an early warm sprmg might be 

 accompanied by a plant louse pest by reason of an earlier reduc- 

 tion of the parasite. 



Control 



Detcnnining JJ'Jicflicr Control Measures Arc Xcccssary 



In view of the facts just presented showing the uncertainties 

 of aphis outbreak, the first pro])lem of the grower is to determine 

 whether the conditions in his orchard render control measures 

 necessarv. If, as spring approaches, the water sprouts, twigs and 

 smaller branches bear no aphis eggs, treatment for lice is un- 

 necessarv, for there will not be sufficient migration from ad- 

 jacent orchards to create an infestation in the first half of the 

 season. If, on the other hand, as spring approaches, aphis eggs 

 are present on the water sprouts, twigs and smaller branches, 

 treatments should l:>e made as a matter of insurance against 

 damage. 



The small black eggs are rather inconspicuous and sharp eyes 

 are required to find the first ones. After the grower lias become 

 familiar with their appearance he can pick them out without 

 difficulty. 



The Problem 



When the eggs are present the jiroblem of contrcilling the 

 various species of apple aphis appears to involve the destruction 

 of the specimens on the trees before they have a chance to do the 

 damage to fruit and foliage. The aphis appears on the trees in 

 the fail (October and Noveml)er), and eggs laid by them carry 

 over the winter until Inid-opening time. The aphis nnist be 

 attacked just before or during egg-laying in the fall, or while 

 still in the form of the egg resting on the bark of the tree, or in 

 the spring as a nymph that has just hatched. 



