INSECT PESTS 229 



increases in yield. Miller (104) reported similar results. In none of these 

 reports was there a clear differentiation between increases from leafhopper 

 and disease control, although leafspot is given as a factor. The same 

 authority ( 106) has reported the potato leafhopper as the most injurious 

 insect of peanuts in Virginia, and stated that sulfur applied for leaf-spot 

 control repelled and controlled leafhopper, even on undusted areas in 

 small-plot experiments. Poos (116) found that 2 percent DDT reduced 

 the infestation of the insect on peanuts and Poos, Grayson, and Batten 

 (120) reported some increase in yield of peanuts and hay from control 

 of leafhopper, but none of the differences was significant. Non-significant 

 increases were also recorded (5) in yield of sound, shelled peanuts in 

 Alabama in 1947 from the use of DDT sprays and dusts on runners. In 

 1948b, however, the dusting of Spanish peanuts 4 times for leafhopper 

 control in Alabama resulted in decreased infestation and in average gains 

 in yield as follows: 2 percent DDT, 302 pounds dry peanuts per acre 

 gain; 2 percent DDT in 90-10 sulfur-copper, 468 pounds per acre; 20 

 percent toxaphene, 470 pounds (7). Two percent gamma BHC and 5 

 percent chlordane were less effective. Four applications of dust to runner 

 peanuts for leafspot and leafhopper control resulted in average gains in 

 yield as follows: Sulfur-copper, 90-10, 264 pounds of dry peanuts per 

 acre; 2 percent DDT, 339 pounds per acre; sulfur-copper plus 2 percent 

 DDT, 444 pounds. Where 10 dustings were made with DDT throughout 

 the season, no significant gains were recorded. In a non-replicated, pre- 

 liminary test, 9 dustings with 20 percent toxaphene for thrips and leaf- 

 hopper control resulted in excellent control of both insects and a 67 per- 

 cent increase in yield over the check. 



Thus it appears that control of potato leafhopper on peanuts is profit- 

 able. It also appears feasible to control leafspot and leafhopper in one 

 operation with a combination insecticide-fungicide. Little is known, how- 

 ever, regarding the relative value of controlling the insect on Spanish, 

 runner and Jumbo peanuts. Little is known regarding the value of con- 

 trol on different soils, although observations indicate that damage is more 

 severe on poor than on more fertile soils ; presumably more profits might 

 be derived from control on the less fertile soils. 



A combination insecticidal-fungicidal dust has been recommended 

 ( 160) for control of leafhopper and leafspot in one operation. The dust 

 rtiixture recommended contains 2.5 percent DDT, 3.4 percent copper, and 

 at least 65 percent sulfur. Four to 5 applications of the dust are applied 

 at approximately 10-day intervals. The last dusting should be 4 weeks 

 before harvest, if the peanut vines are to be used as hay. The DDT-sulfur- 



