Rice Water Weevil Larval Distribution & Damage
Potential - 2010



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Project Leader and Principal  Investigators

Luis Espino, UC Cooperative Extension farm advisor, Colusa, Glenn and Yolo counties




This is the second year of a project evaluating rice water weevil (RWW) larval distribution within rice fields, and assessing potential impact to grain yield. The main goal of this research is to improve management guidelines for RWW control.

Experiments were conducted in commercial rice fields near Colusa and Maxwell in the Sacramento Valley. Rice variety M-206 was grown at both locations. The Colusa site was planted in a no till, stale seedbed, water seeded system. The Maxwell site was water seeded.

Border guidelines adequate

In both locations RWW larval populations were higher in plots near field borders than in plots 100 or 200 feet from the field’s edge. Insecticide applications reduced the number of larvae in treated plots effectively—significantly in plots closer to the edge of the field (where populations were higher). In the plots farther in, differences between treated and untreated plots showed little difference because RWW populations were very low.

Results from experiments conducted in 2009 are consistent with 2010 results. These experiments confirm that edge and levee treatments in California rice are adequate when insecticide applications are needed.

No effect on grain yield

RWW did not affect rice grain yield under the conditions of these experiments. Grain yield wasn’t affected by insecticide treatments. Fertilizer may have influenced yields in some plots where overlapping aqueous ammonia applications were made.


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