Ovipositional Habits of the Rice Water Weevil in California as Related to a Greenhouse Evaluation of Seed Treatments

Abstract

Adults of the rice water weevil, Lissorhoptrus oryzophilus Kuschel, a relatively new pest in California, were collected during May, June, and July for seed-treatment tests in the greenhouse. The parthenogenetic females readily oviposited in the submerged portion of the leaf sheath of the rice seedlings. Plant phytotoxicity was determined and control was evaluated by recording adult mortality, presence of larvae, and plant damage. Aldrin, lindane, Kepone® (decachlorooctahydro-1,3,4-metheno-2H-cyclobuta[cd]pentalen-2-one), NIA 10242 (2,3-dihydro-2,2-dimethyl-7-benzofuranyl methylcarbamate), and GS 13005 (O,O-dimethyl phosphorodithioate S-ester with 4-(mercaptomethyl)-2-methoyx-δ2-1,3,4-thiadiazolin-5-one) controlled larvae or adults or both at 8 oz of active ingredients/100 lb of seed. The 3 last-mentioned insecticides were also tested at one-half this rate, but only NIA 10242 was equally effective at the lower rate. It was not determined if control was the result of contact or systemic action of the insecticides. The 1st-instar larvae would be most susceptible to contact action when they moved from the leaf sheath past the seed to the roots to complete their development.