Diflubenzuron for Rice Water Weevil Larval Control, 1987

The experiment was conducted at the California Rice Experiment Station, Biggs, in 1987 to compare RWW larval control among 3 different rates of diflubenzuron (25% WP). A RCBD was used with 4 replications of 3 rates of diflubenzuron and an untreated control. Treatment plots (6.1 × 11.3 m) were bordered on the north and south by soil levees and on the east and west by 0.7-m tall aluminum sheeting pushed 4-5 cm into the soil. Plots were flooded on 2 May and water-seeded with presoaked seed at a rate of 140 kg/ha on 4 May. Water inlet furrows were closed on 15 May, when plots received application of diflubenzuron using a CO2- pressurized sprayer equipped with a 6.1-m boom. Plants had emerged about 3 cm above the water surface at application time. Water levels receded and remained shallow (1-5 cm) until inlets were re-opened 4 wk later. At other times during the experiment, water depth was maintained at 10 cm. On 22- 23 Jun ten 10-cm diam soil cores per plot (1 plant per core) were removed. Soil was washed from the roots and the number of immature RWW (larvae plus pupae) per core was recorded. Plants removed from the cores were placed in plastic bags, frozen, and later measured and weighed. Plots were harvested by a small field combine on 29 Sep. Grain was air-dried, and yield data were corrected to a seed moisture of 21%.