46 INSECTS OF ECONOMIC IMPORTANCE 



strengths (i to 8) for 3 or 4 successive seasons 

 usually holds this pest in check. Spray for young 

 as they hatch in May or June with nicotine sulphate, 

 ^ pint to 100 gallons water with 4 pounds of soap 

 added or with 10% kerosene emulsion. 



The woolly aphid ^^ {Eriosoma lanigcra) 

 Order — Hemiptera. Manual, p. 162 



It is probably of American origin and became 

 noticeable here about 1850; most serious on the 

 apple; individuals occur on two different parts of 

 the tree; (i) the branches, (2) the roots. The air- 

 living individuals cause scars on limbs but are not 

 considered to be seriously injurious; the root aphids 

 are very injurious to young apple trees when pres- 

 ent on the roots ; they cause swellings on roots and 

 the roots finally decay and trees die; both kinds of 

 individuals secrete a white cottony secretion, hence 

 the name, w^oolly aphid. This pest of the apple is 

 more serious farther south than in New York. 



The woolly aphid has a complicated life history. 

 Some of the winged forms on apple in autumn fly 

 to elm trees w^here the egg-laying females are pro- 

 duced, each of which lays an tgg in a crevice of the 

 bark where it passes the winter and hatches in the 

 spring. The aphids multiply on the elm and cause 

 the leaves to cud. Finally some of the winged 

 forms may fly back to the apple. In the meantime 

 the aphid has maintained its foothold on the apple 

 tree. 



Control — The trunk aphids may be controlled 

 with kerosene emulsion 15%. The root aphids may 

 be controlled with 15% kerosene emulsion. The 

 earth should be removed about each tree to the 

 depth of 3 or 4 inches over a circle with a diameter 

 of 4 feet ; then soak the soil with the emulsion and 



18 Marlatt— U. S. Bn. Ent., Circ. 20. 



