Insecticidal grain protectants can provide control of pest insects during grain storage, but studies which directly compare the efficacy of insecticides in rough rice are few. We examined methoprene, deltamethrin, commercial formulations of methoprene + deltamethrin, ß-cyfluthrin, and diatomaceous earth applied to rough rice over a 6-month period for control of lesser grain borers, Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae), and rice weevils, Sitophilus oryzae (L.) (Coleoptera: Curculionidae). We found that methoprene, deltamethrin, or a combination of the 2 were the most effective controls of both beetles in 22.7-liter metal containers. Damage mass and beetle mass in methoprene-treated rice were reduced by 38% and 55%, respectively, when compared to the nontreated control. Similarly, the mixture of deltamethrin and methoprene reduced damage mass by 32% and total beetle mass by 45% below that of the nontreated control. Deltamethrin reduced total beetle mass by 38% relative to the nontreated rice. In vial assays, only the combination of deltamethrin and methoprene provided control of R. dominica. Diatomaceous earth had the greatest impact upon S. oryzae, but it did not affect R. dominica. Based on these results, a commercial formulation of deltamethrin and methoprene is likely to provide the best overall control of stored grain beetles, though diatomaceous earth may be effective when use of chemical insecticides is undesirable or when S. oryzae is the sole pest present.
Coleoptera , Insecticides , Weevils , Animals , Insecticides/pharmacology , Diatomaceous Earth/pharmacology , Methoprene , Edible Grain
Cultivar resistance is an essential management strategy for the Mexican rice borer, Eoreuma loftini (Dyar), in sugarcane in the USA, but resistance mechanisms are poorly understood. Resistance was evaluated among Louisiana's (USA) commercial sugarcane cultivars and experimental clones through field screenings, greenhouse trials, and a diet incorporation assay. Cultivars L 01-299 and HoCP 85-845 had the lowest borer injury levels, while HoCP 00-950 and L 12-201 were among the most heavily injured in field and greenhouse trials. The variability of results between the two field trials suggests that a genotype × environment interaction might affect the expression of resistance. Oviposition did not differ among evaluated cultivars in the greenhouse choice study. Results from the no-choice experiment showed that neonatal establishment differed among cultivars by up to 3-fold. In a diet incorporation assay, all cultivars reduced larval weight up to 86.5% and increased days to pupation by 1.8-fold relative to the diet-only control. Collectively, these results suggest that Louisiana's sugarcane breeding germplasm contains various resistance levels to E. loftini, emphasizing the importance of screening cultivars before they are released to growers. Future studies should try to determine the influence of environmental factors on resistance expression.
Rice water weevil, Lissorhoptrus oryzophilus Kuschel (Coleoptera: Curculionidae), is a destructive insect pest of rice in the United States. The pruning of rice roots by L. oryzophilus larvae can cause up to 25% yield loss. Currently, insecticidal seed treatments are used in the Louisiana rice industry as a pre-emptive means of controlling this weevil species. Our objective was to gain a better understanding of the spatial distribution of L. oryzophilus in Louisiana rice fields. Thirteen untreated commercial rice fields in Louisiana were mapped using GPS software, and surveyed for L. oryzophilus larvae over two years (2017 and 2018). An ANOVA, spatial interpolation, hotspot analysis, and multiple linear regression were used to determine where populations of L. oryzophilus were concentrated and whether distributions of the pest were related to edge effects. The results showed that L. oryzophilus larvae are typically aggregated along the edges of rice fields, with populations decreasing toward the center of rice fields. Lissorhoptrus oryzophilus densities were 3.3- and 2.2- fold greater along field edges than in field centers in 2017 and 2018, respectively. Hotspot spatial analysis revealed 59% and 32% of low-density clusters occurred at or near field centers, respectively. Multiple linear regression revealed larval densities decline with increasing distance from overwintering sites and alternative habitats (such as tree lines and levees containing bunch grasses and other alternative noncrop plants). These results suggest potential for insecticidal seed treatments to be applied selectively within rice fields to control this pest.
Coleoptera , Insecticides , Oryza , Weevils , Animals , Larva
Louisiana rice is attacked by a complex of lepidopteran stem borers that injure the vegetative and reproductive stages of rice, reducing tillering and grain output. Currently, insecticidal seed treatments are used in Louisiana as a preemptive means to control stem borers in rice. Our objective was to better understand the spatial distribution of stem borers in Louisiana rice fields. Thirteen nontreated commercial rice fields in Louisiana were mapped using GPS software and surveyed for stem borer damage in 2017 and 2018. Damage was recorded by counting the number of blank panicles (whiteheads) within quadrats located at different areas in each field. An ANOVA, spatial interpolation, hotspot analysis, and negative binomial regression were used to determine where stem borer injury was concentrated and whether the distribution of these pests was influenced by rice stand count, field composition, and site location. The results show that stem borers are typically aggregated along field edges, with population density decreasing toward the center of rice fields. Stem borer damage was 4.2- and 3.9-fold greater along field edges than in field centers in 2017 and 2018, respectively. Hotspot spatial analysis revealed 41.7 and 52.1% of low-density clusters occurred at or near field centers, respectively. Negative binomial regression revealed stem borer injury declines with increasing distance from field edges, with regional differences in infestation levels. This suggests stem borer control efforts could be spatially targeted to improve the efficiency of pest management.
Insecticides , Moths , Oryza , Animals , Population Density , Seeds
Cultivar resistance is a key management strategy for the sugarcane borer, Diatraea saccharalis (F.), the primary pest in Louisiana sugarcane, but mechanisms of resistance are not well understood. This research evaluated the potential mechanisms of cultivar resistance to D. saccharalis among commercially produced sugarcane cultivars and experimental lines through three field screenings, two greenhouse experiments, and one diet incorporation assay. The resistant standards HoCP 85-845, HoCP 04-838, and L 01-299 were among the cultivars with the lowest D. saccharalis injury levels in both field and greenhouse trials. Cultivars HoCP 00-950 and L 12-201 were among the most heavily injured in both trials. Differences in oviposition among cultivars in the greenhouse choice study were not detected, suggesting adult preference is not a key factor in resistance. This was also supported by the no-choice greenhouse experiment in which up to 9-fold differences in neonate establishment among cultivars were detected. Larval injury among cultivars in greenhouse experiments was consistent with field studies suggesting traits that affect neonate establishment (e.g., rind hardness) help to confer resistance in the field. In the diet incorporation assay, lower larval weights and longer time to pupation were observed on resistant cultivar Ho 08-9003, but no differences were found among current commercial cultivars. Continuous evaluation of cultivar resistance to D. saccharalis is important in developing effective integrated pest management strategies for this pest. More research into plant characteristics (e.g., leaf sheath tightness and pubescence) associated with resistance is needed.
Moths , Saccharum , Animals , Female , Larva , Louisiana , Oviposition , Pest Control
The sugarcane aphid, Melanaphis sacchari (Zehntner), has emerged as a serious pest of sorghum in the United States. Field trials were conducted in Louisiana and South Carolina in 2016-2018 to investigate its population characteristics and distribution patterns in relation to four sample unit sizes (three circular and one leaf based). Sugarcane aphid populations usually progressed through a phase of rapid rise followed by a phase of rapid decline within a span of 5-6 wk, with peak density determined by sorghum cultivars and climatic conditions. Peak population densities for susceptible cultivars were 1.9-14.9× that for resistant cultivars on a per plant basis. Melanaphis sacchari tended to concentrate on the lower green leaf nodes early in the infestation, with the distribution shifting toward higher green leaf nodes as the infestation progressed. Aphid densities per cm2 at the basal and middle sections were about twice as high as at the distal section of leaves. The proportions of infested sample units were fitted to the Wilson-Room binomial model that incorporates the effect of density on clumping pattern. For a specific sample unit size, clumping patterns were similar across cultivars, years, and leaf positions, but varied across infestation stages. For a fixed aphid density per sample unit, the proportion of infested sample units decreased with increasing sample unit size. For a fixed aphid density per cm2, proportion infested increased with increasing sample unit size, indicating less clumping with a larger sample unit size. Field sampling time and efficiency between samplers were quantified.
Aphids , Sorghum , Animal Distribution , Animals , Louisiana , South Carolina
The sugarcane borer, Diatraea saccharalis (F.), is the primary pest of sugarcane, Saccharum spp., in Louisiana. Recent evidence suggests an integrated pest management (IPM) program has reduced the pest's impact, but the success of this program has not been assessed across the industry. The level of D. saccharalis injury present at harvest was recorded from 388 billet samples from five sugar mills from 2017 to 2019. These results were used to estimate direct and indirect revenue losses from D. saccharalis on the Louisiana sugarcane industry. Insecticide use records were used to estimate control costs and determine total economic impact. The mean percentage of bored internodes was 1.1, 0.3, and 1.7% for 2017, 2018, and 2019, respectively. Direct losses from reduced sugar yield averaged US$4.6 million across years. Indirect losses across years accounted for US$3.0 million and $463,000 for insecticidal control costs and reduced milling efficiency, respectively. The total economic impact of D. saccharalis averaged $8.0 million annually during the three-year study period. This study demonstrates the efficacy of pest management implementation in reducing D. saccharalis injury and highlights the value of IPM. Our findings provide new support for the emergence of D. saccharalis management in the Louisiana sugarcane industry as a modern IPM success story.
Insecticides , Lepidoptera , Moths , Saccharum , Animals , Larva , Louisiana , Pest Control
The rice stink bug, Oebalus pugnax (F.), is the most important pest of headed rice, Oryza sativa L., in the United States. Numerous studies have attempted to quantify the impact of O. pugnax feeding on rice yield and grain quality, but these studies have often produced conflicting results. Across mid-south U.S. rice, thresholds based on sweep net sampling are used to determine the need for insecticide applications, but few studies have related sweep net captures to rice quality parameters. Field trials were conducted in Louisiana in 2015 and 2016 that used different rates of insecticides to establish rice plots with mean O. pugnax infestations ranging from 0.8 to 24.6 insects per 10 sweeps. Insecticide applications improved panicle weight and head yields as well as decreased percentage peck. A series of linear regressions examined relationships between O. pugnax captures and rice yield and quality parameters, including panicle weight, head yield (% whole kernels), and peck (discolored grains). Mean O. pugnax sweep net captures across all sampling dates in both years were significantly and negatively correlated to panicle weight and head yield and positively correlated to percentage peck. Peck was negatively correlated with head yield. Results from sampling at different maturity stages indicate sweep net captures at grain fill and soft dough stages had the greatest influence on rice yield and quality parameters, respectively. Further research into impacts of milling quality reductions on farm revenue and the influence of cumulative infestations over grain development is needed to improve economic thresholds for O. pugnax in rice.
Heteroptera , Insecticides , Oryza , Animals , Edible Grain , Louisiana
BACKGROUND: For the past decade, insecticidal seed treatment has been the most widely used control tactic against insect pests of rice (Oryza sativa L.) in the USA. Seed treatments are used primarily to control the most economically important early-season pest of rice, the rice water weevil (Lissorhoptrus oryzophilus Kuschel). This study was conducted to evaluate the efficacy of reduced rates of chlorantraniliprole seed treatment against the rice water weevil, fall armyworm (Spodoptera frugiperda J.E. Smith), and sugarcane borer (Diatraea saccharalis F.) under field and laboratory conditions. Concentrations of chlorantraniliprole in plant tissues were determined at vegetative and reproductive developmental stages of rice plants. RESULTS: Chlorantraniliprole seed treatment reduced the densities of rice water weevil larvae relative to non-treated controls even at rates 75% lower than the label rate. Increased mortality of fall armyworm larvae was observed at reduced seed treatment rates relative to a non-treated control. Chlorantraniliprole seed treatment increased the mortality of sugarcane borer larvae at all rates relative to controls and the mortality was consistently higher in larvae that were fed stems from treated plants at the vegetative developmental stage than larvae that were fed stems from plants at the reproductive stage. Concentrations of chlorantraniliprole in plant tissues increased with seed treatment rate and decreased with plant age. CONCLUSION: This study has shown that reduced chlorantraniliprole seed treatment rates can provide adequate control against the rice water weevil, fall armyworm, and sugarcane borer, particularly at early developmental stages of rice plants. © 2019 Society of Chemical Industry.
Insect Control , Insecticides , Moths , Oryza/growth & development , Weevils , ortho-Aminobenzoates , Animals , Dose-Response Relationship, Drug , Larva/growth & development , Moths/growth & development , Seeds , Spodoptera/growth & development , Weevils/growth & development
Piercing-sucking herbivores (Insecta: Hemiptera) represent one of the greatest threats to agricultural production worldwide. Hemipteran pests directly injure plants as well as vector disease-causing plant pathogens. Production of sugarcane (Saccharum spp.) in North America is impacted by a complex of Hemiptera including the sugarcane aphid, Melanaphis sacchari Zehntner (Aphididae); yellow sugarcane aphid, Sipha flava (Forbes) (Aphididae); West Indian canefly, Saccharosydne saccharivora (Westwood) (Delphacidae); sugarcane delphacid, Perkinsiella saccharicida Kirkaldy (Delphacidae); and sugarcane lace bug, Leptodictya tabida (Herric-Schaeffer) (Tingidae). None of these pests is consistently damaging to large amounts of sugarcane acreage, but regional outbreaks are common. The biology, ecology, and pest management of these insects are discussed with emphasis on North America sugarcane production.
The Mexican rice borer, Eoreuma loftini (Dyar) (Lepidoptera: Crambidae), is an invasive pest that was first introduced into southern Texas in 1980 and has been expanding its range eastward along the United States Gulf Coast. The pest attacks rice (Oryza sativa L.), sugarcane (Saccharum spp.), corn (Zea mays L.), and other graminaceous crops, and its establishment in Louisiana is expected to have severe economic impacts on crop production. Range expansion and population distribution of E. loftini were monitored with a network of 77 pheromone traps throughout southwestern Louisiana from 2013 to 2015. Eoreuma loftini was ubiquitous throughout the study region, with male moths captured in every habitat sampled. Spatial analysis revealed the population is characterized by high and low density clusters, with the greatest trap captures occurring in southeastern Calcasieu Parish and southern Jefferson Davis Parish. Trap captures in more northern regions of the study were lower than in southern parishes. Trap captures in areas where the pest has been established for >3 yr were greatest in rice habitats. The weighted mean population center moved eastward at a rate of â¼11 km per year. Human-aided movement of E. loftini was probably not involved in the eastward expansion documented during this study. Seasonal population peaks were detected in March-April, July-August, and October-November. This study indicates this species is continuing its spread eastward along the United States Gulf Coast and will likely become established throughout Louisiana within the next 20 yr.
Animal Distribution , Introduced Species , Moths/physiology , Animals , Ecosystem , Louisiana , Male , Population Dynamics , Seasons
The tawny crazy ant, Nylanderia fulva (Mayr) (Hymenoptera: Formicidae), has invaded states of the U.S. including Texas, Louisiana, Mississippi, Alabama, Florida, and Georgia. Native to South America, N. fulva is considered a pest in the U.S. capable of annoying homeowners and farmers, as well as displacing native ant species. As it continues to expand its range, there is a growing need to develop novel management techniques to control the pest and prevent further spread. Current management efforts rely heavily on chemical control, but these methods have not been successful. A review of the biology, taxonomy, ecology, and distribution of N. fulva, including discussion of ecological and economic consequences of this invasive species, is presented. Options for future management are suggested focusing on biological control, including parasitoid flies in the genus Pseudacteon, the microsporidian parasite Myrmecomorba nylanderiae, and a novel polynucleotide virus as potential biological control agents. We suggest further investigation of natural enemies present in the adventive range, as well as foreign exploration undertaken in the native range including Paraguay, Brazil, and Argentina. We conclude that N. fulva may be a suitable candidate for biological control.
The Mexican rice borer, Eoreuma loftini (Dyar) (Lepidoptera: Crambidae), is an invasive pest of sugarcane, Saccharum spp., rice, Oryza sativa L., and other graminaceous crops in the United States. Traps baited with the synthetic female sex pheromone of E. loftini are used for monitoring and management of this invasive pest. However, the active space, or radius of attraction, of these traps is not known. Two field experiments examined the effect of intertrap distance on trap captures with hexagonal arrays of traps deployed in rice stubble habitat in Texas (2011) and Louisiana (2013). Trap capture increased with increasing intertrap distance. Trap interference occurred at intertrap distances ≤50 m in the 2011 experiment. Results from the experiment conducted in 2013 indicate that trap interference occurs at intertrap distances of 50 m, but not at distances ≥100 m. These results suggest that under field conditions, E. loftini pheromone traps attract males from distances of 50-100 m. The active space of pheromone traps also was examined under controlled wind conditions by direct observation of male response to detection of the female sex pheromone. Eoreuma loftini males responded to the pheromone blend by becoming active, fanning their wings, and rapidly walking in circles. The mean distance from the pheromone source at which males responded was 47.6 m. This work provides the first documentation of active space for traps baited with female sex pheromone for a crambid species, and these data will improve pheromone trap deployment strategies for E. loftini monitoring and management.
Insect Control/methods , Lepidoptera/physiology , Oryza/parasitology , Sex Attractants/metabolism , Animals , Behavior, Animal , Female , Male , Mexico , Saccharum/parasitology , Texas
The Mexican rice borer, Eoreuma loftini (Dyar), is a major pest of sugarcane (hybrids of Saccharum spp.) in Louisiana and Texas. Resistance to E. loftini was evaluated in 51 commercial and experimental cultivars of sugarcane, energycane (hybrids of Saccharum spp.), and sorghum [Sorghum bicolor (L.) Moench and hybrids of Sorghum spp.] in four replicated small plot field experiments from 2009 to 2012. A relative resistance ratio was developed to compare levels of susceptibility among cultivars based on the percentage of bored internodes and survival to adulthood. This index was able to separate cultivars into five resistance categories and provides a new method for comparing levels of resistance among cultivars. E. loftini pest pressure in 2009 was among the highest recorded with injury ranging from 55 to 88% bored internodes. Commercial sugarcane cultivar HoCP 85-845 was identified as resistant in three of four experiments, whereas HoCP 04-838 was identified as susceptible in all experiments. Of the five sugarcane cultivars in commercial production in the Rio Grande Valley of Texas, only TCP 87-3388 was categorized as resistant. Of the cultivars with potential for bioenergy production, all of the energycane cultivars demonstrated higher levels of resistance than high-biomass and sweet sorghum cultivars. Continued evaluation of cultivar resistance to E. loftini is important to development of effective integrated pest management strategies for this pest.
Herbivory , Insect Control/methods , Moths/physiology , Saccharum/physiology , Animals , Food Chain , Larva/growth & development , Larva/physiology , Moths/growth & development , Saccharum/genetics , Texas
The Mexican rice borer, Eoreuma loftini (Dyar) (Lepidoptera: Crambidae), is the key pest of sugarcane (Saccharum spp.) in Texas; it can attack several grassy crop and noncrop host plants and has spread into Louisiana. Through small-plot, commercial field, and pheromone trap experiments, this study demonstrates that the pest uses corn, Zea mays L., more than sugarcane and sorghum, Sorghum bicolor (L.) Moench, but when corn is harvested in late summer, injury to nearby sugarcane strongly increases during the next approximately equal to 2 mo to harvest. Corn was more infested than sugarcane and sorghum in commercial fields regardless of whether sampling occurred on field edges or farther into field interiors. Differences in numbers of infested stalks and in numbers of larval entry holes between field edges and interiors were not detected. We found that Mexican rice borer infestation of corn can cause loss of ears, and lodging, shattering, and complete destruction of maturing stalks. The larger quantities of adult Mexican rice borers captured in pheromone-based traps placed at corn field edges compared with sorghum and sugarcane field edges further indicates that corn is preferred to sugarcane and sorghum. The basis for the pest's attraction to corn and implications to potential range expansion to other U.S. sugarcane-growing regions are discussed.
Moths/physiology , Saccharum , Sorghum , Zea mays , Animals , Food Preferences , Larva , Moths/drug effects , Pheromones/pharmacology , Texas
