4 U. S. DEPABTMENT OF ACKICULTURE BULLETIN NO. 484. 



when the larvae are in the very lust stages, but occasionally defolia- 

 tion is effected by caterpillars in earlier stages, in which case the 

 defoliated trees have a better chance to recover, because there re- 

 mains a longer period than usual in which they may grow and 

 recuperate. 



Repeated defoliation from year to year will ultimately kill any 

 tree or render it susceptible to the attacks of bark borers, which 

 produce the same result. In the gipsy-moth region repeated annual 

 defoliation may result from the combined activities of the gipsy 

 moth, brown-tail moth (Euproctis chrysorrhoea L.) , forest tent cater- 

 pillar (Malacosoma disstria Hubn.), and several other common 

 species. Thus, at times when gipsy moths are not abundant, trees 

 previously stripped of foliage by them would doubtless often recover 

 were it not for the activities of other defoliators. Brown-tail moth 

 larvae cease feeding not later than the middle of June, so that de- 

 foliated trees have the advantage of a part of the spring precipi- 

 tation, and more time to recuperate before the end of the growing 

 season. 



Oaks have suffered the highest mortality among defoliated forest 

 trees, probably because of the action of the two-lined chestnut borer 

 {Agrilus bilineatus Weber), whose work is usually p resent beneath 

 the bark of all dead specimens: Many defoliated oaks which have died 

 would doubtless have recovered had it not been for the additional 

 injury produced by this borer. Oaks, more than any other species, 

 are found growing in unfavorable situations in the infested region, 

 which, together with the fact that the infested region includes the 

 northern limit of the range of the white oak, is responsible for many 

 oaks of poor physical condition. Trees in poor condition are par- 

 ticularly liable to serious damage by defoliation, especially in con- 

 nection with attack by the two-lined chestnut borer, which infests 

 only weakened trees. The removal of dying oaks would not only 

 help to reduce a gipsy-moth infestation, but would reduce the num- 

 bers of Agrilus and create room for species of trees for which the 

 situation is more favorable. 



COMPOSITION AND CONDITION OF WOODS IN INFESTED 



TERRITORY. 



At present the gipsy-moth infestation is largely confined to what 

 Hawley and Hawes 1 have designated the White-pine Region. The 

 northern part of the infested region in Maine and New Hampshire 

 extends a little into the " Northern Hardwoods Region," and the 



1 TT.Twloy. It. C, and nawcs, A. F., Forestry in New England ; a Handbook of Eastern 

 Forest Management New York, 1912. 479 p. (P. 196.) 



