Control of Sunflower Moth Larvae and Their Damage to Sunflower Seeds1

Abstract

Investigations on the control of the sunflower moth, Homoeosoma electellum (Hulst), conducted during several seasons have shown that certain insecticides satisfactorily reduced sunflower-head and seed damage when multiple applications were timed properly. Endosulfan and diazinon afforded the most efficient control among the commercially available materials tested. These treatments must begin at onset of bloom and 3 applications at intervals of 5-7 days are optimum. Two applications were a minimum requirement. but 3 were generally needed because of the fast head growth, quick flowering, and concentrated egg deposition during this period. A biological agent was found to be unsatisfactory for control, and only one of several code-named chemicals tested. GS 13005 ( O,O -dimethyl phosphorodithioate S-ester with 4-(mercaptomethyl)-2-methoxy-∆2-1,3,4-thiadiazolin-5-one was outstanding. A new inbred selection of sunflower plants had many advantages for this test work, especially because of its shorter stalks and large heads and seeds. It bloomed early and uniformly for a shorter period; this feature appeared to retard the buildup of infestations and made chemical control easier. One larva severely damaged 9 or more seeds; moderate to severe infestations of 12-24 larvae per head caused serious seed loss. Pesticide control was generally needed for growing the crop, but the actual amount of damage varied from season to season.