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Current pest management practices for the rice water weevil (Lissorhoptrus oryzophilus Kuschel) and the Mexican rice borer (Eoreuma loftini Dyar) in U.S. rice rely heavily on a small number of insecticides. Thus, additional products are needed to delay resistance development and replace products no longer available to farmers. Evaluation of novel and widely used insecticidal seed treatments was conducted in eight small plot field trials from 2015 to 2019 in Louisiana and Texas. Treatments evaluated included the insecticides cyantraniliprole, chlorantraniliprole, thiamethoxam, and clothianidin. Seed treated with chlorantraniliprole and seed treated with both cyantraniliprole and thiamethoxam together provided the best control of L. oryzophilus across trials. Thiamethoxam and clothianidin seed treatments did not provide satisfactory control of L. oryzophilus. Only chlorantraniliprole seed treatment controlled E. loftini. Improved yield was recorded from plots treated with chlorantraniliprole or cyantraniliprole + thiamethoxam across trials from 2017 to 2019 over fungicide only controls. Yield differences among treatments were not detected in 2015–2016 trials. Registration of cyantraniliprole seed treatment for use in U.S. rice provides a new tool for diversification of pest management practices and insecticide resistance management.

The rice water weevil, Lissorhoptrus oryzophilus Kuschel, is the most destructive insect pest of rice in the U.S. This insect poses a global threat to rice production, having invaded rice-producing regions of Asia and Europe. Tolerance is a type of plant resistance that allows crop plants to maintain yield in spite of injury by herbivores. This study was conducted to test the hypothesis that tolerance to L. oryzophilus infestations differs between hybrid and inbred rice cultivars. Field experiments were conducted in Louisiana in 2016–2017 and in multiple locations (Texas, Mississippi, and Louisiana) in 2018. Plant tolerance was assessed by evaluating L. oryzophilus infestations and yields from insecticide-protected and unprotected plots of hybrid and inbred rice cultivars. Infestations of L. oryzophilus negatively affected rice yields, with losses across cultivars ranging from 16.4 to 48.0% in 2016 and 4.2–29.2% in 2017. In the multiple location experiment in 2018, yield losses ranged from 4.1 to 29.7, 7.7–17.2, and 4.5–12.2% in Louisiana, Texas, and Mississippi, respectively. Comparisons of yields between insecticide-protected and unprotected plots indicated that hybrid cultivars exhibited higher tolerance to L. oryzophilus infestations than inbred cultivars in 2016 and 2017. Moreover, in the multiple location experiment in 2018, yield losses were lower in hybrid compared to inbred cultivars in Texas, but no differences in yield losses across cultivars were observed in Louisiana and Mississippi. Rice cultivars expressing tolerance to L. oryzophilus could be used to reduce pest damage in situations where use of insecticides is not practical, too expensive, or only partially effective.

The rice water weevil, Lissorhoptrus oryzophilus Kuschel (Coleoptera: Curculionidae), is the most injurious insect pest in US rice production. Yield losses in excess of 25% can occur from severe infestations. Management demonstrations were conducted in the 2008, 2009, 2010, and 2011 growing seasons to evaluate the use of commercially available insecticides to control L. oryzophilus in commercial rice fields. The demonstration tests, conducted on farms throughout Louisiana, compared the efficacies of recently registered seed treatment insecticides to untreated controls and to foliar applications of pyrethroids. Efficacy was assessed by collecting root/soil core samples three to four weeks after application of permanent flood and counting numbers of larvae and pupae in core samples. Tests were replicated across locations in multiple rice-producing Louisiana parishes. Densities of larvae and pupae in core samples exceeded the larval threshold (three larvae or pupae per core sample) in over 80% of untreated plots/cuts, confirming the ubiquity and severity of this insect as a pest of rice. Use of chlorantraniliprole (Dermacor® X-100, DuPont™ Crop Protection, Wilmington, DE), thiamethoxam (CruiserMaxx® Rice, Syngenta® Crop Protection, Greensboro, NC), and clothianidin (NipsIt Inside®, Valent® USA Corporation, Walnut Creek, CA) seed treatments significantly reduced L. oryzophilus infestation compared to untreated checks. Fewer larvae and pupae were observed in rice treated with chlorantraniliprole than in rice treated with other insecticides.

The rice water weevil (RWW), Lissorhoptrus oryzophilus (Kuschel) (Coleoptera: Curculionidae), is the most destructive insect pest of rice in the United States. Water-seeded rice, which is flooded at an earlier stage of crop development than drill-seeded rice, is at heightened risk of loss from root-feeding RWW larvae. Pyrethroids, the most widely used group of foliar insecticides for RWW control, have inherent limitations such as limited residual activity, narrow window of activity and extreme toxicity to non-target aquatic organisms. An array of field, lab and greenhouse experiments was conducted to compare the activity of two neonicotinoids with that of λ-cyhalothrin, a widely used pyrethroid, against the RWW. Small-plot efficacy trials were conducted during 2009, 2010 and 2011. Foliar clothianidin (Belay 2.13 SC) and a granular formulation (3%) of dinotefuran applied to plots were as effective as, and showed greater residual activity than, foliar applications of λ-cyhalothrin. Topical bioassays on adult weevils revealed that clothianidin possessed lower contact toxicity than λ-cyhalothrin. Residual assays using weevils placed on foliage of sprayed plots revealed that the toxic and sublethal behavioral effects of clothianidian on adult weevils were more persistent for clothianidin than for λ-cyhalothrin. Granular dinotefuran applied to greenhouse-grown plants previously infested with weevil larvae showed excellent larvicidal activity. Overall, these studies showed that neonicotinoids have potential as pyrethroid replacements against the RWW in water-seeded rice culture.

A three-year study was conducted to determine the effect of nitrogen fertilizer rates applied at the panicle initiation stage of rice, Oryza sativa L., and insecticide applications on yield loss caused by rice water weevil, Lissorhoptrus oryzophilus Kushel, damage. Our estimates of yield loss caused by L. oryzophilus injury were, at the recommended nitrogen rate of 191 kg N per ha, 1.7% in 1997, 11.8% in 1998, and 9.9% in 1999. In 1998, doubling the panicle differentiation nitrogen rate from 67 to 134 kg N per ha significantly increased yield by 591 kg per ha, averaged across insecticide treated and untreated plots. In both 1998 and 1999, reducing nitrogen rate below the recommended rate significantly (P 0.05) for yield in any year of our study, suggesting that increasing nitrogen at the panicle differentiation stage does not have a major impact on compensation of the rice plant for L. oryzophilus injury. Our results indicate that farmers should not increase nitrogen fertilizer at the panicle differentiation stage to compensate for L. oryzophilus damage.

The rice water weevil, Lissorhoptrus oryzophilus Kuschel, is the most destructive insect pest of rice in the United States. Two years of field experiments were conducted to quantify relationships between densities of immature rice water weevils and yields for two rice varieties under early and delayed flooding regimes. Larval densities during earlier stages of rice growth were more strongly correlated with yield losses than were larval densities later in the growing season. Slopes of regression models were more negative for early-flood than for delayed-flood plots, and more negative for ‘Bengal’ than for ‘Cocodrie’. The results of these experiments confirm that short delays in flooding reduce yield losses from the rice water weevil and that ‘Bengal’ is less tolerant of weevil feeding than ‘Cocodrie’. Estimates of yield loss caused by each weevil provide a key parameter for the calculation of economic injury levels under different management regimes. Data from this study suggest that it is possible to integrate the use of insecticides, cultural practices and host plant resistance in a management system for the rice water weevil.