Location: Southern Insect Management Research
2016 Annual Report
Objectives
Objective 1: Develop new approaches for the control of noctuid and hemipteran pests of southern row crops, integrating multiple control tactics into integrated pest management systems.
Sub-objective 1.A: Develop new strategies that reduce numbers of insecticide applications on soybean and cotton that are not economically justified.
Sub-objective 1.B: Develop new approaches for the control of insect pests of sweet potato.
Objective 2: Minimize negative effects of integrated pest management systems on pollinators and other beneficial arthropods.
Sub-objective 2.A. Determine the impact of current insect management strategies in corn, cotton, sweet potatoes, and soybean on populations of pollinators and beneficial insects.
Sub-objective 2.B. Examine the acute toxicity, synergistic/antagonistic interactions, and sub-lethal impacts of commonly used pesticides on honey bees using bioassay, biochemical, and molecular approaches.
Objective 3: Improve pest risk assessment by determining environmental influences that affect populations of important insect pests of southern row crops with emphasis on bollworms, tobacco budworms, tarnished plant bugs, stink bugs, and soybean loopers.
Objective 4: Develop methods to measure and manage insecticide resistance of pest populations of southern row crops with emphasis on bollworm, tobacco budworm, tarnished plant bug, and stink bugs.
Sub-objective 4.A. Measure levels of insecticide susceptibilities of tarnished plant bugs, bollworms and other important insect pests of southern row crops through laboratory bioassays.
Sub-objective 4.B. Develop within-field bioassays to determine insecticide susceptibilities of key pests of southern row crops.
Sub-objective 4.C. Examine the impact and sensitivity of resistance management options for major insect pests of southern row crops through simulated modeling.
Approach
Insect management guidelines are generally static from year to year regardless of crop prices, costs of insecticides and yield potential of the crop. We plan to summarize published information for bollworm, tarnished plant bug, and stink bugs and develop economic injury level probability distributions using Monte Carlo simulations. On-farm field evaluations across the Mississippi Delta will evaluate economic returns and environmental sustainability of different insecticidal control strategies in soybean and cotton. Commercially available and experimental sweet potato varieties will be planted annually and the economic impact of insect and nematode control in sweet potato will be examined. The impact of current insect management strategies in southern row crops on populations of pollinators and beneficial insects will be examined in production fields. The surrounding habitats of each field will be documented for plant community composition, focusing on blooming plants that may be of interest to pollinators. Each of these fields will be sampled using a combination of sampling techniques. Community structure will be compared between cropping systems, and related to insecticide applications. We plan to evaluate acute and sub-lethal toxicities and synergistic/antagonistic interactions of honey bees to commonly used pesticides. An examination of gene regulation in honey bees associated with immunity, adaptation, detoxification, digestion/metabolism, and stress-related genes will be conducted after exposure to pesticides with techniques such as real-time PCR , RNAseq or microarrays. Hemipteran and lepidopteran phytophagous pest populations are highly mobile within the landscape and use a variety of weeds and crops as host plants. To examine landscape influences on these insects, the landscape composition surrounding historic and current collection locations will be quantified using Cropland Data Layers (CDLs). Using these CDL layers, buffer zones will be generated around locations. Output data will be tabulated to produce total area of habitat type included within each buffer area and will be related to data collected on insect populations using appropriate statistical analyses. SIMRU will continue to examine susceptibilities of hemipteran and lepidopteran insect pests collected from locations across the Mississippi Delta with a variety of assay methods which may include topically treated diet, residual contact bioassays, glass vial bioassays and a feeding contact assays using floral foam. Insects from original collections will be preserved for molecular analysis using genetic markers. When colonies of any of the pest groups have reduced susceptibility to the tested insecticides, efforts will be made to preserve the colony under a selected and non-selected sequence of exposures to the insecticides of interest We propose to develop rapid bioassays to predict the effectiveness of an insecticide application on a real field population of insects. To examine predictive values of laboratory assays on actual field populations, a plot sprayer will be used to deliver a range of formulated product rates on targeted insects.
Progress Report
Published literature has been examined to develop databases of economic injury levels of bollworms on Bt and non-Bt cotton. The number of peer-reviewed manuscripts detailing this information was much less than anticipated. Literature addressing economic injury levels of bollworms in soybean is currently being synthesized.
Research was conducted to support the 2015 National Sweetpotato variety trials at the Alcorn State University Research Farm in Mound Bayou, MS. The yield and quality of seven sweetpoato varieties grown in the Mississippi Delta were compared. An insecticide efficacy trial to control fall armyworm on sweetpotato was completed. Six recommended insecticides were evaluated. All insecticides caused mortality and resulting damage ranged from 0 to 23 percent.
Collections of native pollinators were made in a variety of agricultural produced commodities including commercial fields of corn, cotton and soybeans as well as small plots of rice and sorghum. Samples were collected utilizing bee bowl units, sweeping, netting, malaise traps, vane traps and by catch from moth pheromone traps. Identification of specimens is ongoing. Some specimens from pheromone trap by catch were determined to be Megachile scultpturalis Smith, an introduced species commonly known as the giant resin bee.
A risk assessment of spray toxicity for 42 commonly used row crop pesticides to adult honey bees was conducted. To assess acute toxicities against honey bees, a modified spray tower was used to simulate field spray conditions that include direct whole-body exposure, inhalation, and continuing tarsal contact and oral licking after a pesticides application. Acute spray toxicities of these 42 pesticides were examined for 4-6 day old worker honey bees. The ratios of field use concentration to lethal concentrations that incur 1% bee toxicity and lethal concentrations that incur 99% mortality were adopted as a way to assess practical and real risk to honey bees for the pesticides examined. The development of toxicity baselines for the pesticides examined will facilitate further studies on pesticide toxicology in honey bees. Additionally eight of these pesticides were examined for acute toxicity, sub-lethal toxicity, and potential synergistic toxicity to honey bees using spray and feeding treatments. One insecticide from five different insecticide classes, a fungicide, and an herbicide were tested individually and in combination with imidacloprid. Survivors were subjected to analyses of esterase, glutathione, S-transferase, phenoloxidase, and invertase activities. Results indicate that imidacloprid mainly acts as a nerve toxin, and incurs no significant adverse physiological impact on bees below ppm levels. Most other pesticides at residual levels did not synergize imidacloprid activity against honey bees, but synergistic toxicity was detected after the concentrations of each pesticide was increased.
Historical data from tarnished plant bug susceptibility to commonly used insecticides have been digitized and are being analyzed for trends over time. Additional data from these studies are being analyzed for landscape interactions of tarnished plant bug susceptibility to the insecticide, novaluron and cotton acreage in the surrounding area of insect collection sites.
Current insecticide susceptibilities of tarnished plant bugs and bollworms are being evaluated through laboratory bioassays. Feral tarnished plant bug adults were collected weekly across the MS Delta. Insects were bioassayed comparing several different methods including diet incorporation (a new method for this insect species) versus a traditional contact assay method (glass vial bioassays). Insecticides used were permethrin, imidacloprid, acephate, thiamethoxam, and sulfoxaflur. Using the contact assay methods in 2015 to compare to historical data since 2008, tarnished plant bugs were assayed to the major insecticide classes. Average LC50s expressed as ug of insecticide for acephate, imidacloprid, permethrin and thiamethoxam per vial were 7.4, 1.7, 1.6, and 2.2, respectively for the 2015 field growing season. Early season populations of bollworm were collected from crimson clover at seven locations in Arkansas, Louisiana, and Mississippi and examined for susceptibilities to lambda-cyhalothrin, chlorantraniliprole, and acephate through diet incorporation bioassays. Assays are currently in progress and data is being summarized.
Residual activities of two microbial insecticides (Dipel and Gemstar) and two chemical insecticides (Karate and Prevathon) were measured by bioassay of field treated cotton. Both microbial insecticides showed reduced residual activity after one-day of exposure to field conditions. Prevathon showed no decline in residual activity over the 16 days of observation.
Accomplishments
1. Toxicity of pesticides to honeybees. The development of toxicity baselines of 42 pesticides to honey bees was established. This will facilitate further studies on pesticide toxicology in honey bees.
None.
Review Publications
Portilla, M., Snodgrass, G.L., Street, D., Luttrell, R.G. 2015. Demographic parameters of Nezara viridula (L.) (Heteroptera: Pentatomidae) reared on two diets developed for Lygus spp. Journal of Insect Science. 15(1):165. doi: 10.1093/jisesa/iev144.
Perera, O.P., Allen, K.C., Jain, D., Purcell, M., Little, N., Luttrell, R.G. 2015. Rapid identification of Helicoverpa armigera and Helicoverpa zea (Lepidoptera: Noctuidae) using ribosomal RNA internal transcribed spacer 1. Journal of Insect Science. 15(1):155. doi:1093/jisesa/iev137.
Luttrell, R.G., Teague, T.G., Brewer, M.J. 2015. Cotton insect pest management. In: D. D. Fang and R. G. Percy (Eds.) Cotton. Agronomy Monograph 57, American Society of Agronomy, Crop Science Society of America, Soil Science Society of America, Madison, WI. Book Chapter. Pp. 509-546.
Portilla, M., Jones, W.A., Perera, O.P., Seiter, N., Greene, J., Luttrell, R.G. 2016. Estimation of median lethal concentration of three isolates of Beauveria bassiana for control of Megacopta cribraria (Heteroptera: Plataspidae) bioassayed on solid Lugys Spp. Diet². Insects. 7(3):31. doi: 10.3390/insects7030031.
Perera, O.P., Walsh, T.K., Luttrell, R.G. 2016. Complete mitochondrial genome of Helicoverpa zea (Boddie) and expression profiles of mitochondrial-encoded genes in early and late embryos. Journal of Insect Science. 16(1):40. 1–10. doi: 10.1093/jisesa/iew023.
Seymour, M., Perera, O.P., Fescemyer, H.W., Jackson, R.E., Fleischer, S.J., Abel, C.A. 2016. Peripheral genetic structure of Helicoverpa zea indicates asymmetrical panmixia. Ecology and Evolution. 6(10):3198-3207. doi: 10.1002/ece3.2106.
Parys, K.A., Tripodi, A.D., Sampson, B.J. 2015. The giant resin bee, Megachile sculpturalis Smith: new distributional records for the mid- and gulf-south USA. Biodiversity Data Journal. 3:e6733.
