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In the southern US rice is often managed for production of a second, or "ratoon" crop, with minimal input costs. The impact of rice insect pests including the rice water weevil, Lissorhoptrus oryzophilus , and a complex of Lepidopteran stem borers during the main or ratoon crop on ratoon crop yields is unknown. A series of field trials was conducted from 2021 to 2023 to evaluate the influence of insecticidal protection on pest infestations and yields in both the main and ratoon crops. Insecticidal seed treatments reduced infestations of L. oryzophilus in the main crop by 20% (thiamethoxam-treated) and 65% (chlorantraniliprole-treated) relative to non-treated controls. Chlorantraniliprole seed treatments reduced stem borer injury by 80% relative to thiamethoxam-treated and non-treated plots. Main crop yields were 9.7% greater in plots protected with insecticides relative to non-treated plots. Neither insecticidal seed treatments nor foliar insecticides applied in the ratoon crop affect pest densities in the ratoon crop. Densities of L. oryzophilus across treatments were 2–5-fold greater in the main crop than ratoon crop. No benefits of insecticidal seed treatments or foliar insecticides were observed in ratoon rice yields. Collectively, results suggest management of insect pests in the ratoon crop is of reduced economic importance relative to the main crop. Protection from root and stem injury during the main crop has little to no benefit on ratoon crop production. Benefits of controlling insect pests in the ratoon crop remain unknown. • Insecticidal seed treatments reduced L. oryzophilus densities in the main crop. • Chlorantraniliprole seed treatments reduced densities of Lepidopteran stem borers in the main crop. • Insecticidal seed treatments improved main crop yield, but did not impact ratoon yield. • Neither foliar- or seed-applied insecticides affected insect pest desnities in the ratoon crop. • Management of insect pests in the ratoon crop is of minimal economic importance relative to the main crop. [ABSTRACT FROM AUTHOR]

The rice water weevil Lissorhoptrus oryzophilus Kuschel (Coleoptera: Curculionidae) is a worldwide agricultural pest that causes serious damage to rice. The olfactory and gustatory behaviors of L. oryzophilus in locating host plants and oviposition sites mostly rely on the detection of chemical stimuli in the environment. To reveal such olfactory and gustatory systems, we performed a systematic analysis of major chemosensory receptor genes. The antennal transcriptome of adult female L. oryzophilus was sequenced and assembled using the Illumina sequencing platform. A total of 60 candidate chemosensory receptor genes were ultimately identified, including 41 putative odorant receptors (ORs), 10 ionotropic receptors (IRs) and 9 gustatory receptors (GRs). Relatedness with other species was predicted based on phylogenetic results, and specific chemosensory receptor genes were analyzed, including Orco, carbon dioxide receptors and sugar receptors. Furthermore, qRT-PCR analyses of chemosensory receptor genes showed 59 genes to be antenna-biased genes, whereas only 1 gene was predominantly expressed in non-olfactory tissues. Our research provides insight for understanding olfactory and gustatory systems in the antennae of L. oryzophilus and facilitating the discovery of novel strategies for controlling this pest. Unlabelled Image [ABSTRACT FROM AUTHOR]

The rice water weevil (RWW), Lissorhoptrus oryzophilus Kuschel, is one of the most destructive pests causing heavy rice yield loss worldwide. In the present study, amplified fragment length polymorphism (AFLP) was used to analyze the genetic differentiation and transmission routes of 26 RWW geographical populations from Guizhou and 6 other provinces in China. The genetic distance between the 26 populations ranged from 0 to 0.693; the genetic distance between Guizhou and 6 other provinces populations varied from 0.043 to 0.693, with an average of 0.382. There was higher genetic variation among the populations from Guizhou and 6 other provinces compared with populations within Guizhou. The Mantel test showed no correlation between the genetic and geographical distances of the 26 populations. According to genetic distance, clustering, and time that RWW was found in these regions, we deduced that the pest entered Guizhou and spread in this province most likely via three routes: (1) from Hebei to Zunyi and southward to the south-central regions; (2) from Sichuan to Bijie and eastward to the central regions; and (3) from Yunnan through Anshun to the central regions and Qiandongnan prefecture. RWW spread in a natural manner, including flight, crawling, swimming, and by human-associated mechanisms, comprising dissemination through paddies and hay and hitchhiking on human transportations. [ABSTRACT FROM AUTHOR]

The use of multiple insecticidal seed treatments in combination to control a greater spectrum of pests has been increasing in rice production in the U.S. Mid-South. The economic benefits of individual seed treatments in rice are well documented, but returns on investment (ROI) on combinations are unknown. Efficacy and economic returns of insecticidal seed treatments alone and in combination were evaluated through a series of five field trials conducted in Louisiana from 2018 to 2020. In all trials, treatments containing chlorantraniliprole or cyantraniliprole provided the best control of rice water weevil, Lissorhoptrus oryzophilus Kuschel (Coleoptera: Curculionidae), and control was not significantly improved by the addition of a second insecticide. Insecticidal control of L. oryzophilus by all seed treatments was reduced in late-planted rice fields relative to rice planted within the recommended planting window. Control of the Mexican rice borer, Eoreuma loftini (Dyar) (Lepidoptera: Crambidae), did not improve rice yields. Fungicidal seed treatments generally protected rice yields over treatments without fungicides despite having no effect on early-season plant populations. All seed treatments provided returns on investment which ranged from $94.30 (fungicide only 2018) to $519.75/ha (chlorantraniliprole + thiamethoxam + fungicides in 2019–2020). Increased yields resulting from the use of multiple insecticides in combination appears to justify the added expense. Collectively, results demonstrate the immense value of insecticidal seed treatments to rice production in Louisiana and throughout the U.S. Mid-South. Future research efforts should aim to assess returns on seed treatments across a range of rice production conditions and to quantify the impacts of sporadic pests on rice yields. • The use of insecticidal and fungicidal seed treatments is economically justified in rice production in the southern U.S. • Economic returns on seed treatments result primarily from control of the rice water weevil, Lissorhoptrus oryzophilus. • The use of multiple seed treatments in combination may improve economic returns over the use of single treatments alone. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: The rice water weevil, Lissorhoptrus oryzophilus Kuschel, is the most important species among invasive insects in China. The parthenogenic weevil, first detected in Tanghai County of Hebei Province in 1988, has become one of the major rice pests in China with yield loss of 10–80%. Since then, the pest has expanded its range of infestation at a rate of 10–30km/year. This pest has been found in eleven provinces and two large municipal areas infesting over 400,000ha by late 2003. Quarantine measures did not effectively limit the spread of rice water weevil due to its parthenogenesis, flying, swimming and hitchhiking on human transportation. The weevil''s life history, population dynamics, host–plant relationships and mode of establishment have been studied at a number of locations. Currently, the pest is managed by integration of insecticides, water management, delayed transplanting, blacklight trapping, application of Beauveria bassiana and Metarhizium anisopliae spores and rice cultivars with tolerance to the rice water weevil. [Copyright &y& Elsevier]

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. [Copyright &y& Elsevier]

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. • Cyantraniliprole seed treatment effectively controlled Lissorhoptrus oryzophilus. • Improved control was achieved by cyantraniliprole together with thiamethoxam. • Cyantraniliprole was not effective against the stem borer, Eoreuma loftini. • Registration of cyantraniliprole provides U.S. rice farmers a new pest management tool. [ABSTRACT FROM AUTHOR]