Gypsy Moth •* ^ 



This Old World species, brought into Massachusetts in 1868, did not infest 

 the Cape cranberry region seriously till 1913. During 1913 and 1914 it increased 

 vastly there, becoming the important cranberry pest it still continues to be. It 

 usually is most harmful on the outer Cape. 



Distribution and Food Plants 

 This pest ranges widely through Eurasia and North Africa. In our country 

 it still is confined to New England and areas in New York and Pennsylvania. 

 It has hundreds of food plants. 



Character of Injury 



The young worms commonly attack the terminal buds first, eating all but the 

 outer scales (fig. 3?) and often causing great loss before the grower knows his 

 bog is infested. As the new growth develops, the caterpillars greedily devour 

 the leaves, flower buds, and blossoms (fig. 36) and often sever the new part of 

 the stem (fig. 37). They attack the old foliage severely when they are very 

 abundant and have destroyed the more attractive new growth, and sometimes even 

 gnaw bark from the vines. 



The work of this insect on cranberry vines is much like that of the false 

 armyworm in all stages. This is true of no other pest. 



An infestation of two first-stage worms to the square foot often develops 

 so as to destroy nearly all the new growth, and one larva to the square foot 

 usually reduces the crop materially. 



Bogs usually do not yield well till the second year after severe injury by this pest, 

 but vigorous vines often do so the next year. 



Descriptioyi and Seasonal History 



THE EGG 



The eggs are smooth, globular, about a twentieth of an inch in diameter and 

 pale pinTcish brown when first laid. They grow darker within three weeks 

 when fertile, owing to the development of the worms. They are laid soon 

 after the moths emerge, mostly in oval or rounded masses of four hundred to 

 sometimes over a thousand (Plate Four, fig. 12). These are half an inch to 

 an inch and a half long and a third of an inch to an inch wide. They are 

 covered with yellowish hairs from the abdomens of the moths and look like 

 pieces of sponge. They are laid in every conceivable place, but the trunks and 

 branches of trees probably arc the most natural locations. They usually are 

 placed within a few inches of the pupal case from which the female moth emerged. 



The young worms become fully formed within three weeks after the eggs 

 are laid. They cannot endure a temperature lower than -25 °F. and often are 

 winterkilled extensively in northern New England. Some hatch in September 

 in rare instances, but they normally appear from the last of April to mid- 

 June, according to the weather and their position, those in warm sunny places 

 coming out earliest while those in cool shady locations emerge much later, 

 most of them usually hatching between the 12th and the 25th of May. 



The winter flowage of bogs does not harm the eggs much as long as it is 

 cold, for they hatch readily afterward if it is let off early in April. If it is 

 held till after May 20, the hatching is negligible. 



THE WORM 



The caterpillars in their first stage are very dark and, being clothed with 

 long hair and provided with aerostatic hairs, are borne easily by the wind. It 

 sometimes carries them twenty miles or more. 



^ Porthetria dispar (L.). See U. S. Dept. Agr. Dept. Bui. 1093, 1922. 



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