Evaluation of Vantacor insecticide against the rice water weevil (Lissorhoptrus oryzophilus) (Coleoptera: Curculionidae) in drill-seeded and water-seeded rice, 2023

The rice water weevil (Lissorhoptrus oryzophilus) continues to be the most economically significant pest in mid-southern rice production. Larvae prune rice roots which significantly reduces nutrient uptake, tiller production, and yield. Neonicotinoid and anthranilic diamide seed treatments are the most common and effective way to control L. oryzophilus larvae. Continued evaluations of chemical efficacy, for both insecticidal seed treatments (ISTs) and foliar-applied insecticides, are ongoing to support L. oryzophilus management in rice. Two experiments were planted with cultivar ‘PVL03’ to evaluate Vantacor insecticide (chlorantraniliprole, FMC Corp., Philadelphia, PA) as a foliar treatment in drill-seeded, delayed-flood rice (planted 31 Mar) in addition to impregnation on urea fertilizer in water-seeded rice (planted 12 May). Each test was arranged in a randomized complete block design with 4 replications. Field plots were 4.67 ft × 16 ft and seeded at a rate of 60 and 100 lbs/a in drill-seeded and water-seeded tests, respectively. Plots in the drill-seeded test were planted with 7 rows on 8 in centers. Rice was hand-sewn into flooded field plots for the water-seeded test. For all foliar treatments, insecticide was applied with a CO₂-pressurized backpack sprayer calibrated to deliver 15 gal/a using 3 TeeJet 11001VS spray nozzles at 30 psi. Insecticidal seed treatments were prepared as a slurry and mixed with seed in large mason jars placed on motorized rollers. The seed/slurry mixture was allowed to tumble for 10 min until the seed was fully coated. Experimental treatments in the delayed-flood test were Dermacor X-100 seed treatment (1.75 fl oz/a) (chlorantraniliprole, Corteva Agriscience, Indianapolis, IN), Cruiser 5FS seed treatment (2.2 fl oz/a) (thiamethoxam, Syngenta, Wilmington, DE), foliar-applied Warrior II at pre-flood (2.56 fl oz/a) (lambda-cyhalothrin, Syngenta, Wilmington, DE), Cruiser 5FS seed treatment (2.2 fl oz/a) + foliar-applied Vantacor at planting (1.7 fl oz/a), Cruiser 5FS seed treatment (2.2 fl oz/a) + foliar-applied Vantacor pre-flood (1.7 fl oz/a), foliar-applied Vantacor alone at planting (1.7 fl oz/a), foliar-applied Vantacor alone pre-flood (1.7 fl oz/a), and an untreated check. Experimental treatments in the water-seeded test were Dermacor X-100 seed treatment (1.75 fl oz/a), Cruiser 5FS seed treatment (2.2 fl oz/a) + Vantacor (1.7 fl oz/a) impregnated on urea fertilizer (250 lbs/a), Vantacor alone (1.7 fl oz/a) impregnated on urea fertilizer (250 lbs/a), foliar-applied Vantacor alone pre-flood (1.7 fl oz/a), and an untreated check. In both tests, L. oryzophilus larvae densities were quantified using a 4 in diameter × 3 in deep soil core (average of 3 cores/plot at 2 core dates). Roots of cored plants were washed through a 40-mesh sieve to facilitate L. oryzophilus larvae collection. Data were subjected to a generalized linear mixed model to test the effect of insecticide treatment on L. oryzophilus larvae densities for each experiment, separately. Rep was treated as a random effect and means were separated using Tukey’s HSD (α = 0.05).

The mean number of L. oryzophilus larvae/soil core in the delayed-flood and water-seeded tests was 13.9 and 15.9, respectively. Differences among treatments were detected in the delayed-flood test, however, foliar treatments regardless of application timing did not achieve greater control than treatments containing an insecticidal seed treatment (Table 1). No significant differences were detected in the water-seeded test (Table 2).¹

Footnotes