Abstract
Insecticide applications for control of the alfalfa weevil, Hypera postica (Gyllenhal), were made in the spring and fall using various materials in spray and granular formulations. None of the fall treatments (October) provided satisfactory control and neither heptachlor nor dieldrin were so effective against the weevil as they had been 2 years previously. Malathion and azinphosmethyl spray treatments applied in the spring (April) at 1.0 and 0.75 Ib per acre, respectively, provided the best protection against alfalfa weevil larvae. Several unregistered insecticides showed some promise for weevil control; these were: SD 4072 [2-chlor-l-(2,4-dichlorophenyl) vinyl diethyl phosphate]; SD 7438 (benzylidene methyl phosphorodithioate); American Cyanamid 47470 [2-(dicthoxyphosphinylimino)-4-methyl-1,3-dithiolane]; American Cyanamid 47772 [2-(dimethoxyphosphinylimino)-4 methyl-],3-dithiolane]; Imidan® ( O, O -dimethyl S -phthalimidometbyl phosphordithioate); and dimetilan.
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