351 "^ 



N 



691. Nemec, S. J. 1970. Topical applications and caged-plant evaluations of 

 insecticide toxicities to bollworms, tobacco budworms and boll weevils. 

 Tex. Agric. Exp. Stn. Consol. Prog. Rep. PR 2840-2845, pp. 14-18. 

 Laboratory tests were conducted to deternine the toxicities of certain insecti- 

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

 virescens (F.) and boll weevil, Anthonomus grandis Boheman. Increased resis- 

 tance in 1969 to methyl parathion and Azodrin was detected in tobacco budworms 

 from Weslaco and College Station, Texas. The LD^q value for methyl parathion 

 in 1969 increased 1 1/2-fold over 1968 and 3-fold over the 1967 LD^^ value 

 for tobacco budworms from the Brazos River Valley near College Station. The 

 LDcQ value of methyl parathion for tobacco budworms from Weslaco in 1969 was 

 2-fold greater than in 1968 and 5 1/2-fold greater than the LD50 value esta- 



y 



blished for College Station larvae in 1967. Similar increases in resistance '~/' 



to Azodrin® by tobacco budworms from both areas of the state were also observed. 



The LDcQ values obtained for the bollworm in 1969 did not change significantly 



from the LDrQ values established during the previous 4 years. Therefore, the 



bollworm has developed no apparent resistance to methyl parathion or Azodrin. 



Most of the insecticides tested in caged plant tests produced effective control 



of bollworm larvae. These included the organophosphates methyl parathion, 



Azodrin and Monitor; the carbamate, Sevin, and certain mixtures of insecticides. 



The chlorinated hydrocarbon insecticides tested without the addition of organo- 



phosphorus insecticides were Ineffective. Extremely high dosages of methyl 



parathion and Azodrin were required to kill significant percentages of 



tobacco budworms on sprayed cotton plants. The organophosphorus insecti- \ 



cides and a carbamate were the most toxic materials to boll weevils. \ 



/ 



