2 4 
. —_— i 
‘ A ow > 
ae. 
A. 
Tell By 
Dw agian er piak 
ry 
hb Oo 
U.S. D. A., B. E. Bul. 68, Part IT. ‘ D. F. I. L, July 6, 1907. 
PAPERS ON DECIDUOUS FRUIT INSECTS AND INSECTICIDES. 
THE SPRING CANKER-WORM. 
(Paleacrita vernata Peck.) 
By A. L. QUAINTANCE, 
In Charge of Deciduous Fruit Insect Investigations. 
INTRODUCTION. 
Two species of canker-worms in the United States, the spring 
eanker-worm (Paleacrita vernata Peck) and the fall canker-worm 
(Alsophila pometaria Harr.), are often very troublesome pests in 
apple orchards, infesting also the elm, cherry, and, to a less degree, a 
few other trees. These insects, though widely distributed, usually 
occur in injurious numbers quite locally, infesting often but one or 
two orchards in a neighborhood where conditions have been favorable 
for their development. The females of both species are wingless, 
hence their dissemination is very slow. The insects are doubtless 
distributed mostly on nursery stock in the egg stage, or locally the 
larve and moths may cling to clothing of persons, or may be dis- 
tributed by teams visiting the infested orchards. 
Old orchards which hae been in sod or have not been cultivated 
for many years and which are not sprayed with arsenicals furnish 
‘ideal conditions for the multiplication of canker-worms when the 
latter are once established. Frequently such orchards are defoliated 
each spring, with the result that the injury to the trees prevents the 
formation of fruit buds, and after a few years of such injury the 
trees will begin to die. While certain weather conditions and the 
natural enemies of canker-worms may often greatly reduce the num- 
ber of these insects, energetic steps on the part of the orchardist are 
usually necessary to insure the complete destruction of the pests and 
to permit the trees to resume their normal fruit production. In the 
great majority of cases, if not in all, canker-worms are practically 
limited to orchards which are neglected as to spraying and cultiva- 
tion, either practice usually serving to keep them so reduced in num- 
bers that their injuries are inconsequential. 
17 
