Evaluation of Dimilin in Water And Drill-Seeded Rice For Rice Water Weevil Control, 1996

Dimilin ap plied at different rates, formulations, and times was evaluated for control of adult RWW at the Rice Research Station, Crowley, LA. Plots, 5 X 20 ft, were arranged in a RB design with 4 blocks and 8 treatments with sub-sample nesting within the block X treatment effect. Fertilizer application in the water-seeded test was incorporated pre-plant and applied broadcast 6 wk post-flood at 90 lb (23-12-12) and 55 lb (21 -0-0) N-P-K/acre respectively. Fertilizer application in the drill-seeded test was broadcast at permanent flood and 6 wk post-flood at 90 lb (23-12-12) and 55 lb (21-0-0) N-P-K/acre respectively Plots were either water-seeded with pre-soaked ‘Cyprus’ rice at 130 lb or drill-seeded with ‘Cyprus’ rice at 100 lb of seed/acre to Crowley silt loam. The water-seeded test was planted on 22 May, drained 24 May, and permanently flooded 28 May. The drill-seeded test was planted 1 May and permanently flooded 21 May. Weed control was accomplished in the drill-seeded test by applying 0.5 and 4.0 lb (AI)/acre of Basagran and Stam on 20 May, respectively. Gramoxone was applied at 0.625 lb (AI)/acre to the water-seeded test on 20 May to control weeds. Foliar applications of Dimilin 2L and 25W were made at various rates and applied at 0 or 0 and 5 days post-flood. Furadan 3G was applied 19 and 7 days post-flood at 0.6 lbs (AI)/acre using a hand-held shaker for the water and drill-seeded tests respectively. All pesticide applications except Furadan 3G were made using a CO2 backpack sprayer delivering 15 gpa at 28 psi with 110015VS flat-fan nozzles on a 3 ft boom. Three randomly selected soil samples per plot were taken 10, 17 and 25 Jun for the water-seeded test and 5 and 12 Jun for the drill-seeded test using a 4 X 4 inch core sampler. Individual samples were washed through a funnel, fitted with wire screen, into a 35 mesh screen sieve. Collected rice water weevil (RWW) larvae and pupae were floated in a saturated NaCl solution, and counted. The center four rows of each plot were harvested on 11 Sep using a Kubota combine. Moisture content of harvested grain was determined and standardized to 12% moisture for determination of yield (lbs/acre). Rice water weevil larval data were log transformed to improve normality before being subjected to analysis of variance. The experimental and sampling error terms for the RWW larval data were tested for homogeneity of variances, and pooled error terms used to test the treatment effect when appropriate. Treatment means were separated using protected least significant difference at (LSD) 0.05. Non-transformed data are presented in the tables.