an estimated 1,500,000 acres were defoliated in the New England 
area. Losses through mortality of defoliated trees have been 
great. From 1933 to 1952, they amounted to an estimated 2,279,- 
819 cords and 128,951,000 board-feet of merchantable timber, hav- 
ing a total estimated value of $4,223,556 (592). 
Gypsy moth damage is not confined to the killing of trees. 
Heavy losses in reduced growth of surviving trees are also in- 
curred (592). Continued defoliation also causes loss of tree vigor, 
leading to attacks by secondary insects and fungi. Surviving trees 
are often stunted, ill-formed, and unmerchantable. Further losses 
result from the reduction in quality of forest sites in stands 
suffering repeated defoliation.!* in increased fire damage, in the 
impairment of watersheds, and in reductions in esthetic, recrea- 
tional, and wildlife values. 
When the gypsy moth was introduced, the insect parasites, 
predators, and pathogens affecting it in its native habitats abroad 
were left behind, and it encountered none here that were capable 
of holding it in check. To remedy this situation, a program of 
importation of foreign parasites and predators was initiated 
in 1905 and continued intensively for about 25 years (128, 387). 
Collections representing 45 different species of the parasites and 
predators were imported, colonies of which were released in in- 
fested stands in this country. Nine species of the parasites and 
two of the predators became established. Two are hymenopterous 
egg parasites—Dencyrtus kuwanat (How.) and Anastatus dis- 
paris Ruschka; four are tachinid larval parasites—Compsilura 
concinnata (Meig), E'xorista larvarum (L.), Parasetigena agilis 
(R.-D.), and Blepharipa scutellata (R.-D.) ; three are hymenop- 
terous larval parasites—Phobocampe disparis (Vier.), Apanteles 
melanoscelus (Ratz.), and Monodontomerus aerus Wlkr.; and two 
are coleopterous predators—Calosoma sycophanta (L.) and Cara- 
bus auratus (L.). The current status of these enemies of the gypsy 
moth and effectiveness in its control are discussed by Dowden 
(205). 
One of the most important factors affecting heavy gypsy moth 
populations is the so-called ‘‘wilt’’ disease, caused by a nuclear- 
polyhedral virus, Borrelinavirus reprimens. This pathogen is also 
a native of Europe. It is believed to have entered this country in 
gypsy moth larvae imported for the recovery of parasites. Dur- 
ing moth epidemics it increases tremendously and _ practically 
wipes out populations over large areas. It occurs only rarely in 
light infestations; thus, is ineffective in preventing outbreaks. 
Other natural control factors include low winter temperatures— 
exposed eggs are unable to withstand temperatures lower than 
—?25° F (697). Late spring frosts kill newly hatched larvae, and 
rodents devour large larvae and pupae found on the forest floor. 
Many larvae also die of starvation in woodlands entirely stripped 
of foliage before the larvae reach maturity. Bess (63) and Camp- 
bell (133) discuss the population dynamics of the species. 
Silvicultural practices designed to promote the health and 
vigor of stands is helpful in increasing tree resistance to gypsy 
12 House, W. P. 1952. Appraisal of damage by the gypsy moth in New 
England, 1933-52. Unpublished report, U. S. Dep. Agr., Bur. of Entomol. 
and Plant Quar., Greenfield, Mass., 22 p. 
323 
