INSECTS AFFECTING FIELD CROPS 501 



"horn-blowers." During the summer the pupal stage lasts 

 about three weeks, and there may be two or even three genera- 

 tions in the south. 



The insect passes the winter in the pupal stage. Many of 

 the pupae can be destroyed by thorough plowing and harrowing. 

 As the larvae are usually easily detected on the plant, hand-pick- 

 ing is the common method of control where labor is cheap. 

 Paris green dusted or sprayed over the plants has long been a 

 favorite remedy, but as this sometimes burns the foliage, ar- 

 senate of lead is now more commonly used. From four to six 

 pounds of arsenate of lead to 100 gallons of water are 

 the proportions usually recommended. 



These same horn-worms are often important enemies of 

 tomatoes. 



The Tobacco Flea-beetle (Epitrix parvula). This small, 

 black flea-beetle looks much like flea-beetles more commonly 

 found on tomatoes, potatoes and other garden plants. Indeed, 

 this species does, not restrict itself to tobacco, but may often 

 be found on other plants in the field and garden. The beetles 

 feed on the foliage, and, when abundant, may do considerable 

 damage, particularly to young plants. The slender, whitish 

 larvae usually feed on the roots of weeds, but they sometimes 

 attack the roots of garden plants also. They pupate in the 

 soil when fully developed. There are probably several genera- 

 tions each year. 



If the field is kept free from weeds there will be less oppor- 

 tunity for the larvae to find food. Where the beetles appear in 

 destructive numbers the plants should be sprayed thoroughly 

 with arsenate of lead, five or six pounds of the poison to 100 

 gallons of water. The tops of the young plants may be dipped 

 into an even stronger solution of the poison just before they 

 are set out if there is danger of the flea-beetles attacking them 

 early. 



The Tobacco Leaf -miner (Phthorimaa operculella.} This 

 little larva, which is only about half an inch long, lives between 

 the upper and lower epidermis of the leaves causing them to 

 split. This has suggested the popular name of "split-worm" 

 for the pest. Sometimes the larvae come to the surface and 



