THE SO-CALLED TOBACCO WIREWORM IN VIRGINIA. 6 



The principal species of the genus of economic importance in this 

 country are: Crambus caliginosellus Clemens, which attacks tobacco 

 and corn; C. vulgivagellus Clemens, an enemy of corn, wheat, rye, 

 and grasses; C. trisectus Walker, an enemy of grasses, oats, and corn; 

 C. laqueatellus Clemens, which attacks corn and oats; C. zeellus Fer- 

 nald, C. luteolellus Clemens, and C. mutabilis Clemens, enemies of 

 corn; and C. hortuellus Hiibner, which is injurious to the cranberry. 

 The wide distribution of several of these and their great capacity for 

 injury give them rank as species of considerable economic impor- 

 tance. Damage by them to cultivated crops is, in most cases, the 

 result of unusual conditions. Their range of food plants is not 

 large, and the larvae are inclined to remain in or near one place. 

 The moths frequent the weedy fields, pastures, or meadows which 

 contain the natural food plants of the larvae, and the greater num- 

 ber of eggs are deposited in such localities. When such land is 

 plowed up the larvae are forced to live on other than their natural 

 food plants. With crops such as corn and tobacco this means a 

 concentration of larvae from many of the wild or natural food plants 

 to the comparatively few cultivated plants. 



ECONOMIC IMPORTANCE OF THE TOBACCO CRAMBUS. 



The tobacco Crambus (Crambus caliginosellus Clem.) occurs in 

 most, if not all, of the tobacco-growing districts of the Eastern 

 States, but it seems to be most destructive in certain sections of 

 Maryland and Virginia. It is especially destructive in the famous 

 "dark-tobacco district" of the Piedmont section of middle Virginia, 

 although found in all sections of the State in which tobacco is 

 grown. In Virginia the damage to the tobacco crop alone from 

 the insect is estimated to average at least $800,000 annually. 



At the Virginia tobacco experiment, stations, at Appomattox, 

 Bowling Green, and Chatham, injury has been recorded for a num- 

 ber of years. The reduction in value of the crop has been great, 

 amounting to about 14 per cent annually, through failure to secure 

 an early stand of plants. At the Appomattox Station, in one of 

 the experimental fields, there was a loss in 1910 amounting to 

 about 27 per cent. In 1911 there was still greater loss in some 

 of the plats. In many fields in the county fully one-half of the 

 plants were attacked, making several replantings necessary. At 

 the Chatham Station in 1909 there was an estimated decrease in 

 the value of the crop amounting to about $15 per acre. 



In 1912 considerable damage occurred to tobacco in Montgomery 

 County, Tenn., and in Christian and Todd Counties, on the south- 

 ern border of Kentucky, growers in a number of instances report- 

 ing fully 40 per- cent of the plants destroyed. 



