INSECTS INJURIOUS TO THE APPLE AND PEAR 607 



the summer generations on clover are pink or yellowish, with 

 a large pale orange spot around the base of each honey-tube. 

 Concerning this species Gillette and Taylor give the following: 

 "' The clover aphis, A. bakeri, infests the cultivated and sweet 

 clovers and alfalfa throughout the wanner part of the year where, 

 apparently, it never occurs in the oviparous form nor as eggs. 

 In the fall a portion of the winged lice migrate to apple and pear 

 trees, where eggs are deposited to live over winter and hatch into 

 the red stem mothers the following spring/' hatching a week or 

 two before the apple-aphis. " The descendants of these stem 

 females begin in the second generation to get wings and by the 

 middle of June nearly all have left the trees and gone back to the 

 clovers, though some remain on the apple all summer. In the 

 fall, many of the lice continue upon the clovers, going down close 

 to the ground as cold weather comes on, and if the winter is not 

 very severe, many will survive and continue to live and increase 

 upon these plants throughout the year. So far as our observa- 

 tions have gone this louse ranks next to the green apple-aphis 

 (Aphis pomi) in numbers as a leaf-infesting species of the apple, 

 . . . but we can hardly consider it a serious pest as yet in Colorado 

 orchards." Evidently the life history closely parallels that of the 

 previous species, S. avence. 



Control. Recent experiments have shown that lime-sulfur 

 wash applied while the trees are dormant, as for the San Jose 

 scale, will kill nearly all aphid eggs. Pure crude petroleum has 

 also proven effective against the eggs in several experiments. 

 Recently Professor Gillette has reported * experiments which 

 indicate that tobacco extracts will destroy the eggs when used at 

 various dilutions according to the strength of the extract, but 

 though these preparations may be effective, further field experi- 

 ments will be necessary to determine the exact dilution best for 

 orchard use. Spraying for the aphides after they hatch should be 

 done before they commence to curl the leaves, preferably just as the 

 foliage is expanding, for after the leaves are curled it is impossible 

 to reach them with the spray successfully. Kerosene emulsion 

 * C. P. Gillette, Journal of Economic Entomology, Vol. Ill, p. 207. 



