Evaluation of Dimilin for Rice Water Weevil Control, 1995

Abstract

Abstract Dimilin was evaluated for control of adult rice water weevil at the Rice Research Station, Crowley, LA. Collectively levied plots, 5 X 20 ft, were arranged in a RBD with 4 blocks and 5 treatments with sub-sample nesting within the block X treatment effect. Fertilizer was incorporated pre-plant and applied broadcast 3 wk post-flood at 90 lb (13-13-13) and 50 lb (21-0-0) N-P-K/acre respectively. Plots were water seeded 29 May with pre-soaked ‘Cyprus’ rice at 138 lb seed/acre to Crowley silt loam and permanently flooded 8 Jun. Foliar applications of Dimilin 25 W were made at 0.25 or 0.125 lb (AI)/acre. Furadan 3 G was applied at RWW threshold (5 larvae/sample) at 0.6 lb (AI)/acre using a hand-held shaker. Dimilin 25 W applications were made using a CO2 backpack sprayer delivering 15 gpa at 16 psi with 80015VS flat-fan spray nozzles on a 3 ft boom. Rice water weevil eggs were counted from 5 randomly selected plants per plot beginning 2 d after flood then weekly until RWW threshold. Three randomly selected soil samples per plot were taken 26 Jun, 3 and 11 Jul using a 4 X 4 in core sampler. Individual samples were washed through a funnel, fitted with wire screen, into a 35-mesh screen sieve. Collected RWW larvae and pupae were floated in a saturated NaCl solution, and counted. Rough rice yield (lb/acre) was determined by hand-harvesting one random 3-ft2 sample per plot on 19 Sep. Moisture content of harvested grain was determined and standardized to 12% for determination of rough rice yield. RWW larval data were log transformed to improve normality. All data were subjected to ANOVA. Experimental and sampling error terms for the RWW larval data were tested for homogeneity of variances, and pooled error terms were used to test the treatment effect when appropriate. Protected least significant difference (LSD) was used for treatment mean separation.