246 APPLIED ENTOMOLOGY 



stem but later almost anywhere on it. About 200 eggs (Fig. 241c) 

 are laid singly, and these hatch in from 1 to 2 weeks. The larvae 

 now bore into the stem and feed, generally working toward the base of 

 the plant, making holes through it to the outside here and there, through 

 which some of the excrement is expelled. They become full-grown (Fig. 

 24 Id) in about 4 weeks and then go a few inches into the ground to 

 pupate, making dark-colored silken cocoons (Fig. 241/) mixed with dirt. 

 Some soon pupate (Fig. 24 le) while others remain as larvae in their 

 cocoons until the following spring. After the pupal stage has been 

 completed the pupa works through the cocoon and to the surface of the 

 ground and the moth then emerges from its pupal skin. 



In the South there are two generations a year of this insect: far- 

 ther north there is a partial second generation, and in the northern 

 part of its range there is only one, winter in any case being passed in the 

 ground. 



The injury caused by these insects when they are abundant is serious. 

 The burrows become wet and slimy, hastening decay and thus separating 

 much of the plant from its roots. The feeding also interferes with the 

 circulation of the sap to some extent. A sudden wilting of the leaves is 

 generally an indication of the presence of the borers, and coarse yellowish 

 excrement beneath the stems is also evidence of their activity. In some 

 cases entire fields of the plants have been killed by the work of this 

 pest. 



Control. — Sprays tried thus far have proved ineffective. As the 

 winter is spent in the ground of the field where the insects fed, it is evi- 

 dent that their food plants should not be planted 2 years in succession 

 on the same land. Light harrowing of infested fields in the fall to bring 

 up the cocoons and expose them to winter surface conditions, followed 

 by spring plowing to a depth of at least six inches has given good results. 

 Planting a few plants of very early varieties of summer squash as a trap 

 crop on which the insects may lay their eggs before the real crop is 

 available for them, followed by the destruction of the trap plants before 

 the larvae are full-grown is helpful. Covering the stems with earth to 

 induce the production of roots from the nodes along the stem will often 

 enable an attacked plant to continue to grow even after its connection 

 with its original roots has been destroyed. Finally, when borers are 

 found in the stems they may be cut out, using a sharp knife and splitting 

 the stem lengthwise where the borer is and removing it, then covering 

 the stem thus treated with moist earth to aid it in healing the wound. 



Many other injurious insects belong in this family, among which the 

 Imported Currant Borer boring in currant stems and killing them; the 

 Blackberry Crown Borer which bores in the roots and crown of the black- 

 berry and raspberry and has a 2-year life history; and the Maple Sesian 

 which bores in the trunks of maples, may be mentioned. 



