Minimum Effective Level of Methiocarb for Protecting Sprouting Rice in Louisiana from Blackbird Damage

Blackbirds cause locally serious losses to rice. The Denver Wildlife Research Center, U. S. Fish and Wildlife Service, and the Rice Research Station, Louisiana State University Agricultural Center have been cooperating in tests to determine the efficacy of methiocarb seed treatments for protecting sprouting rice in Louisiana from blackbird damage. Results from four field tests (1980, 1982, 1983, and 1984) have shown that methiocarb provides good protection when applied to rice seed at the rate of 2.4 g and 1.25 g active ingredient (a.i.)/kg of rice seed (0.25 and 0.125%). Seed treated at 0.6 g a.i./kg appeared to be susceptible to damage; but, results were inconclusive due to low bird pressure on untreated fields. Fields planted with seed treated at 0.4 g a.i./kg were heavily damaged. Laboratory testing substantiated that >1 g of methiocarb/kg was required to achieve acceptable repellency. We recommend that future field testing be restricted to treatments of >1.0 g a.i./kg rice seed, and that >1.0 g a.i./kg be accepted as the minimum seed treatment level for formulations under consideration for registration or use in conjunction with emergency (Section 18) exemptions to FIFRA by the Environmental Protection Agency.