9 



terous parasites. Under certain weattier conditions entire colonies 

 may be destroyed by funoous diseases. During periods of rainy 

 weather the insect enemies of aphides are much less active than when 

 the weather is fair. This is particularly true of the minute delicate- 

 winged hymenopterous parasites, to which such weather conditions 

 are largely fatal. With the coming of fair weather, however, these 

 foes of aphides soon multiply, quickly reducing their hosts to much 

 less injurious numbers. 



METHODS OF CONTROL. 



Pruning. — As has been stated, the aphides under consideration pass 

 the winter in the egg stage on the apple, the eggs being deposited 

 more or less promiscuously over the more nearl}- terminal twigr. 

 With young trees especially, which are seen to be heavily stocked 

 with the eggs, the latter may be largely removed during the work of 

 pruning, and the prunings should be collected and burned. 



The insects in the egg condition are frequently distributed on nurserj^ 

 stock; therefore, if in planting trees this stock be well pruned and the 

 prunings destroyed, the establishment of the aphides in young orchards 

 maj' be often prevented or dela^'ed. 



Winter spraying for destruction of eggs. — Several sprays have been 

 at various times more or less used for the destruction of the eggs on 

 the trees; among these are strong lye water, whale-oil soap, and kero- 

 sene and crude petroleum — in soap or mechanical emulsions with water 

 or even undiluted. On the whole, very little of practical good seems 

 to have followed these treatments, the eggs being largely resistant to 

 such insecticides as are not so strong as to injure the trees. In the 

 experience of Prof. J. M. Aldrich, however, excellent results have 

 followed the use of lime-sulphur wash, most all of the eggs of the apple 

 aphis having been destroyed by one thorough, application in spring 

 shortly l)efore the buds opened. The use of this wash for the eggs of 

 aphides would also control the San Jose scale when present. 



Spring mid summer treatments. — Effective work in controlling these 

 insects may be done in the spring just after the}^ have hatched from 

 eggs and have collected on the expanding foliage. Trees seen to be 

 badly infested at this time should be thoroughly spraj^ed, taking pains 

 to wet as completel}" as possible all parts of the leaves, twigs, and 

 branches. However thoroughly the work ma\' be done, some of the 

 *'lice" are almost sure to escape destruction, owing to the difficulty of 

 forcing the spray between the unfolding leaves, more or less covered 

 with hairs, where some of the insects will have penetrated. A subse- 

 quent treatment in the course of a week should usually be made, espe- 

 cially if the first application is seen to have been unsatisfactory. 



After the foliage is well out and more or less distorted from the 

 presence of the aphides, effective spraying is quite difficult, since 



[Cir.81] 



