Location: Southern Insect Management Research
2019 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
Participated in the 2018 sweet potato variety trials at the Alcorn State University Research Farm in Mound Bayou, Mississippi. This ongoing research effort compares the yield and quality of sweet potato varieties and their compatibility for production in the Mississippi Delta. Lines included varieties from Louisiana and North Carolina. This information is being used by local sweet potato producers and others in the southern U.S.
Knowledge related to the species composition and abundance of native bees in agricultural and non-agricultural portions of the Mississippi Delta is lacking. Collections of native bees were continued in commercial fields of corn, cotton, sorghum, sunflowers, and soybean located across the Mississippi Delta. Additionally, specimens were collected from selected non-agricultural areas including fallow fields, roadside ditches, and National Wildlife Refuges in the Mississippi Delta. Samples were collected with a combination of collection techniques including modified pan traps (bee bowls), malaise traps, and net sampling. Additional specimens were added from bycatch of other studies including moth pheromone traps. Over 30,000 specimens have been cleaned, pinned, and mounted, and entered into a database. Specimens of species new to the state or of particular significance have been deposited with regional and national entomological museums. This baseline information is being used to examine potential impacts of local agricultural production practices on these insects.
Potential synergistic toxicities of pesticide mixtures are increasingly a concern to the health of crop pollinators, especially honeybees. The toxicities of individual and mixtures of three different pesticides (chlorpyrifos, acephate, and tetraconazole) with nine pyrethroid insecticides were evaluated to examine potential toxicities to honeybees. There were some synergistic toxicities detected to honeybees when combinations of these pesticides were mixed with the various pyrethroid insecticides.
Insects have different intoxication and detoxification systems to activate or degrade toxic chemicals. Acetamiprid is a selective neonicotinoid insecticide with a relatively low toxicity to honeybees. A study was conducted to examine the impact of acetamiprid mixed with various pesticides on honeybee mortality. Among the 98 mixtures tested, it was found that some exhibited synergistic effects on honeybees. Although the toxicity of acetamiprid is low, mixtures with commonly used pesticides can aggravate toxicities to honeybees.
The susceptibilities of over 100 field populations of tarnished plant bugs to five different classes of insecticides commonly used in the Mississippi Delta were examined. Insecticides tested included: acephate, permethrin, imidacloprid, thiamethoxam, and sulfoxaflor. These laboratory tests are used to predict field control on cotton and to detect populations that may develop resistance to these insecticides.
Current insecticide susceptibilities of lepidopteran pests of the Mississippi Delta were continued. Insect populations were collected from wild and cultivated host plants throughout the growing season. Insecticides tested included lambda-cyhalothrin, chlorantraniliprole, and spinosad. Various instars of bollworm larvae were examined to determine how susceptibilities of these insects to diamide insecticides change over the life of larvae. The risk of development of insecticide resistance to diamide insecticides by bollworms and tobacco budworms under different usage scenarios is being explored through computer model simulations.
Accomplishments
1. Comparison of laboratory methods to estimate levels of tarnished plant bug resistance. The tarnished plant bug is a major pest of cotton in the southern U.S. and the target of multiple insecticide applications each season. Adequate field control using commonly used insecticides is uncertain due to populations having various degrees of susceptibility to these insecticides. Three different laboratory tests were compared by ARS scientists in Stoneville, Mississippi, to determine the susceptibility of tarnished plant bugs to commonly used insecticides. It was corroborated that these existing procedures are adequate for tracking tarnished plant bug resistance, but field studies are needed to relate laboratory tests to field control.
Review Publications
Sappington, T.W., Hesler, L.S., Allen, K.C., Luttrell, R.G., Papiernik, S.K. 2018. Prevalence of sporadic insect pests of seedling corn and factors affecting risk of infestation. Journal of Integrated Pest Management. 9(1):16. https://doi.org/10.1093/jipm/pmx020.
Hull, J.J., Perera, O.P., Wang, M. 2020. Molecular cloning and comparative analysis of transcripts encoding chemosensory proteins from two plant bugs, Lygus lineolaris and Lygus hesperus. Insect Science. 27:404-424. https://doi.org/10.1111/1744-7917.12656.
Blanco, C., Finkenbinder, C., Morris, A., Blenderman, D., Portilla, M. 2018. Simple methods to devitalize eggs and larvae of Heliothis virescens and Helicoverpa zea under laboratory conditions. Southwestern Entomologist. 43(3):563-569. https://doi.org/10.3958/059.043.0301.
Portilla, M., Luttrell, R.G., Parys, K.A., Little, N., Allen, K.C. 2018. Comparison of three bioassay methods to estimate levels of tarnished plant bug (Hemiptera: Miridae) susceptibility to acephate, imidacloprid, permethrin, sulfoxaflor, and thiamethoxam. Journal of Economic Entomology. 1-10. https://doi.org/10.1093/jee/toy244.
Zhu, Y., Yao, J., Adamczyk Jr, J.J. 2018. Long term risk assessment on noneffective and effective toxic doses of imidacloprid to honey bee worker. Journal of Applied Entomology. 143:118-128. https://doi.org/10.1111/jen.12572.
