'■UTir* I ti-mnMMawMm-rB*w«— fci' .■ ■ wbm.i.ii ii.i—in ■ i ■, i ■! .m, l» -ii nil irir iiiir III I niii nil I -iir - II Mif- -ri]M-|iT"T^"~ ' ■ ■■^— ,-. 



352 



692. . .1971. Laboratory investigations of insecticide effectiveness 



againiJt bollworms, tobacco budworms and boll weevils. Tex, Agric. Exp. 

 Stn. I'2p. Entomol. Tech. Rep. 19, pp. 33-37. 

 Laboratory studies were conducted to evaluate the toxicities of certain 

 insecticides to the bollworm, Heliothis zea (Boddie), tobacco budworm, 

 Heliothis virescens (F.) and boll weevil, Anthonomus grandis Boheman. 

 Resistance to methyl parathion and monocrotophos by tobacco budworms from 

 two areas of Texas was substantially greater in 1970 than in 1969. The 

 LDcQ value for methyl parathion for tobacco budworms from the Brazos Valley 

 near College Station was twofold greater in 1970 than in 1969 and 14-fold 

 greater than in 1964. The LDcq value established for methyl parathion for 

 tobacco budworms from Weslaco in 1970 was 0.46 milligrams per gram. This 

 value is almost fourfold greater than that established in 1969 and 46-fold 

 greater than the LD-f, established for tobacco budworms in 1964 from College 

 Station. Similar increases in resistance to monocrotophos by tobacco bud- 

 worms from both areas of the state were also observed. The LDcq values 

 obtained for the bollworm in 1970 did not change significantly from the LD3Q 

 values established during the previous 7 yea'-s. This indicated that boll- 

 worms have not developed any detectable resistance to methyl parathion or 

 monocrotophos. The organophosphorus and carbamate insecticides gave high 

 mortalities oF bollworms at moderate test dosages in caged plant tests. The 

 chlorinated hydrocarbon compounds were generally ineffective against the 

 bollworm when used singly, but when used in combination with methyl parathion 

 their effectiveness was enhanced. Extremely large dosages of most insecti- 

 cides did not provide adequate mortality of tobacco budworms on treated plants. 

 The organophosphorus and carbamate insecticides were the most toxic 

 materials to boll weevils. 



\ 



- \. 

 \ 



