INSECTS INJURIOUS TO STONE FRUITS 665 



spraying with whale-oil soap, 1 pound to 6 gallons of water, or 

 by the addition of quassia chips, which has long been the favorite 

 remedy of hop-growers, 6 to 8 pounds of quassia chips are 

 steeped in cold water for a day or two and then boiled for an 

 hour, when they are mixed with 4 or 5 pounds of soft soap, whale- 

 oil soap being excellent, and 100 gallons of water. 



The Rusty-brown Plum-louse * 



This species is readily distinguished from others common on 

 plum and prune by the dark rusty-brown color, with the base 

 of the antennae, tibiae, and tail a contrasting white. This species 

 has become a very serious pest to plum foliage in the South and 

 Southwest, and we have observed serious injury in New Hamp- 

 shire, so that it is evidently widely distributed. The aphides 

 collect on the tender young twigs, which they stunt or kill, assemble 

 on the under sides of the leaves, which become corrugated and 

 curled from their attack, and when abundant they attack the 

 blossoms and their stems and thus prevent the setting of fruit. 

 In early summer the winged females migrate to various common 

 grasses, such as fox-tail, red top, barnyard grass, crab grass, and 

 others, upon which they breed during the summer, and from which 

 the winged forms return to plum in the fall. They become 

 darker in color late in the season and the wingless, egg-laying 

 female is almost black, as is also the small winged male. 



Control. The treatment advised for the apple-aphis (p. 658) 

 will be effective for the three species above while on the plum, 

 and for that and other species, the spraying should be done 

 early in the season before the aphides have become numerous 

 and curled the foliage. 



* Aphis setarice Thos. Family Aphididce. See Gillette and Taylor, 

 Bulletin 133, Colo. Agr. Exp. Sta., p. 41; C. E. Sanborn, Bulletin 88, Okla- 

 homa Agr. Exp. Sta. 



