594 INSECT PESTS OF FARM, GARDEN AND ORCHARD 



mate with winged males which have developed on hops, the 

 winter eggs being laid on the plum and other species of Prunus. 

 In California, Clarke has been unable to find any evidence of 

 the species on plum or other vegetation outside of the hop yards, 

 where he finds the true sexes occuring in the fall, but no evidence 

 of eggs. Hops are often seriously damaged by being reduced in 

 size and weight and from the loss in aroma due to the presence 

 of the aphids in them. The species is of European origin, where 

 it is a well-known enemy of hops, and has become widely dis- 

 tributed in the United States and Canada. 



Control. Where it oviposits on plum it may be best con- 

 trolled by spraying as for the other plum aphids in the spring. 

 After it becomes established on hops it may be controlled by 

 spraying with "Black-leaf 40." 



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 aphids 

 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. 537) 

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

 and the spraying should be done early in the season before the 

 aphids have become numerous and curled the foliage. 



* Aphis setaricB 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. 



