GIPSY MOTH AND BROWN-TAIL MOTH AND THEIR CONTROL. 5 



FOOD PLANTS 



The most favored food plants of the gipsy moth are the apple, the 

 different species of oak, gray birch, alder, and willow. In cases of 

 had infestation nearly all of our deciduous trees are injured to a 

 greater or less extent, with the exception of ash. Hickory is not a 

 favored food plant, although the foliage occasionally shows severe 

 feeding. Chestnut will not support the gipsy moth when the cater- 

 pillars are in the first stage, and pine will not support the first two 

 .Mages: but if other food plants are present severe injury may result 

 from feeding by the larger caterpillars. Beech is sometimes fed upon 

 freely, and occasionally the trees are defoliated; and the same is true 

 of poplar. 



INJURY CAUSED BY THE GIPSY MOTH. 



Unless reduced in numbers by natural enemies, or by the applica- 

 tion of control measures, the gipsy moth is capable of causing enor- 

 mous injury to tree growth. In the area in New England which has 

 suffered most from this insect thousands of trees are dead as a result 

 of defoliation. (See fig. 3.) Apple and oak have been injured most, 

 but pine and other coniferous trees mixed with deciduous growth have 

 suffered severely. 



It is undoubtedly true that many oak trees which have been se- 

 verely weakened as a result of defoliation by the gipsy moth and the 

 brown-tail moth have failed to recover because of the attacks of cer- 

 tain wood-boring insects. The species which has caused the most 

 damage in this way is Agrilus bilineatus Web., a beetle the larva of 

 which feeds beneath the bark of injured trees. 



NATURAL ENEMIES. 



There are few insect enemies of the gipsy moth native to New 

 England that cause any noticeable benefit in reducing its numbers. 

 This is shown by the fact that between the years 1900 and 1905, when 

 no systematic effort was made to suppress the insect, alarming injury 

 resulted, and native insect enemies did not increase to any marked 

 degree. The same is true of the work of native insectivorous birds. 

 While they undoubtedly feed to some extent on gipsy-moth cater- 

 pillars, there is no case on record where they have been able to control 

 the species. The wilt disease, which possibly may have occurred in 

 this country for many years, has only recently become sufficiently 

 abundant to be a prominent factor in natural control. 



INTRODUCED PARASITES AND ENEMIES. 



In 1905 an effort was made by the State of Massachusetts, in co- 



I operation with the Bureau of Entomology, United States Department 



of Agriculture, to introduce the parasites and natural enemies of the 



