If the damage appears significant and you feel treatment is needed based on observed plant symptoms, drain the field and confine the application to those areas where larvae are present and plant growth is noticeably stunted. The later the paddy draining and treatment are delayed, the more difficult it will be for the plants to recover. Plants have recovered to provide adequate yields with treatments made as late as 8 weeks after planting, but expect a delay in grain maturity dates with late treatments. In fields that perennially show damaging populations of the rice water weevil, it may be advisable to make a preventative preplant insecticide treatment of carbofuran for the weevil before flooding the field. Limit this treatment to areas near the field margins or levees where the greatest weevil activity was observed and recorded in your monitoring program the previous year.
Warrior works by killing the adults, therefore reducing the number of eggs and larvae.
Rice plants are protected by the reduction of larval populations. Dimilin functions by sterilizing adult rice water weevil females, which causes them to lay nonviable eggs, thus reducing the larval populations. It also is toxic to newly laid eggs. Because there is only one generation a year, timing is critical with both of these products to optimize control efficacy. Confine the treatments to those parts of the field where the number of weevil scars is above the threshold or where injury is indicated by plant symptoms.