BULLETIN No. 203. 



ELM LEAF CURL AND WOOLLY APPLE APHID.* 

 EDITH M. PATCH. 



The dual personality of certain ap'hid species is a condition 

 which, before it is detected, betrays the economic entomologist 

 into many futile combative attempts ; but on the other hand the 

 same duality may reveal, when once discovered, the most vul- 

 nerable point of attack. It is not necessary to go out of our 

 own state for illustrations. The discovery that Chermes abieti- 

 colens Thomas 1879 which makes cone-like galls on black and 

 red spruce is the same species as Chermes pinifoliae Fitch 

 1858,** which lays eggs on new growth white pine for progeny 

 that render the pine shoots weakened and unthrifty, gives the 

 landscape gardener his clue. If he treasures the beauty of a 

 group of white pines he would do well to exclude red and black 

 spruces from the vicinity, or conversely if he wishes to grow 

 black spruces with normal branches it is an indiscretion to place 

 them near white pines. Again, when once it was ascertained 

 that the common Alder Blight, Pemphigus tessellata Fitch 

 1851, was masquerading on the maple (Acer saccharium L. 

 dasycarpum Ehrh. and cultivated varieties) as Pemphigus 

 accrifolii Riley 1879,+ the owner of ornamental cut leaved 

 maples had a theretofore unsuspected means of protecting their 

 foliage by the control of the pest on its alternate food plant, the 

 alder, which in many circumstances is an easy point of control. 



The economic application of the case in hand is apparently 

 as direct and simple as the two just cited and since we are here 

 concerned with one of the most serious of the apple tree pests, 



* Papers from the Maine Agricultural Experiment Station : Entomol- 

 ogy No. 58. 



: * Bulletin 173 Maine Agricultural Experiment Station. 



t Entomological News, 1908, p. 484; Journal of Economic Entomology 

 1909, Vol. II, p. 35 ; Bulletin No. 195 Me. Agr. Exp. Sta., Feb. 13, 1912. 



