INSECTS INJURIOUS TO THE APPLE AND PEAR 587 



beaks, so that they take no food. The female is a brown-ochre 

 color, and the male dark green or greenish-brown and smaller, 

 as shown in Fig. 443. They become full grown in about eight 

 days, when they mate and the female then lays a single large black 

 egg, which is deposited in the crevices of the bark on the lower 

 part of the trunk. These eggs hatch in the spring and give rise 

 to new colonies. 



As they multiply large galls are produced on the roots, the 

 tissue probably being poisoned by the mouth-parts of the 

 insects. As a result the roots soon die and the aphides then 

 migrate to the growing roots, so that their absence on the worst 

 knotted roots does not indicate that they have forsaken the 

 tree, but that they are on younger roots. 



Control. Nurserymen commonly apply a liberal amount of 

 tobacco dust in trenches along the rows, which kills the aphides 

 and acts as a repellant, as well as being worth half its cost as a 

 fertilizer. This is probably the best practice in the nursery unless 

 the aphides become abundant, when more vigorous treatment 

 should be used, but tobacco has not always proven a satisfactory 

 treatment for orchard trees, though used with apparent success 

 in some instances. The aphides may be destroyed on the foliage 

 by spraying with 7 per cent kerosene emulsion, miscible oils 

 diluted 30 to 40 times, whale-oil soap, 1 pound to 6 gallons, or 

 tobacco extracts, " black leaf " being used 1 part in 70 of water. 

 Whatever insecticide is used must be applied in a strong spray 

 so as to thoroughly wet and penetrate the waxy covering of the 

 aphides. A winter spray of lime-sulfur wash destroys the hiber- 

 nating aphides on the trunk, and doubtless kerosene emulsion or 

 miscible oils applied in early spring, as for the San Jose Scale, 

 would be as effective, though the lime sulfur would probably also 

 destroy some of the eggs. The trunks of trees known to be 

 infested may be banded with tanglefoot or similar sticky 

 materials as described for canker worms (p. 574) to prevent 

 the aphides from migrating from the roots to the top. Where 

 the aphides are abundant on the roots, the earth should be removed 

 for 6 or 8 inches deep over the affected roots and 10 per cent 



