Location: Southern Insect Management Research
2024 Annual Report
Objectives
1. Determine current insecticide susceptibilities of major insect pests of row crops in the Southern United States and develop methods to manage insecticide resistance.
1.A. Determine current insecticide susceptibilities of tarnished plant bugs, bollworms, and other major insect pests of row crops in the Southern U.S. through laboratory bioassays.
1.B. Examine insecticide resistance management strategies for insecticides with varying decay rates.
1.C. Identify and characterize resistance mechanisms involved in organophosphates, carbamates, pyrethroids and neonicotinoids resistance.
2. Evaluate the impact of agronomic practices (water management, plant nutrition and cultural practices) on tri-trophic interactions to optimize insect pest management in Southern row crops
2.A. Evaluate the impact of water management practices (oxygenated water or nanobubbles) on plant nutrition, root health, crop production and yield, pest management and other above and belowground tri-trophic interactions in Southern row crops.
2.B. Investigate the effect of arbuscular mycorrhizal fungus (AMFs) and fungal endophytes on improving plant nutrition, host plant resistance and pest management in Southern row crops.
3. Develop and evaluate novel methods of insect control that can be integrated for optimum effectiveness and determine the sustainability of using multiple insect control tactics together.
3.A. Evaluate methods of insect control as substitutes to synthetic insecticides in row crops of the MS Delta.
3.B. Develop new approaches for the control of insect pests of sweet potato.
3.C: Develop new approaches for the control of insect pests of row crops of the MS Delta.
4. Determine population genetic characteristics of crop pests and beneficial insects including pollinators.
5. Develop and evaluate new bio-control strategies to control sucking insects in cotton crops by focusing on the use of entomopathogenic fungi and nematodes, viruses, and parasitoids.
5.A. Quantify the impact of natural control on mirid and pentatomid insect pests’ seasonal abundance and distribution.
5.B. Identify and develop new biological control options including entomopathogens and TPB egg parasitoids, as possible regulators of sucking insect pest populations.
6. Develop and implement semiochemical-based trapping methods to monitor populations of insect pests and their natural enemies in cotton cropping systems.
Approach
Studies will be carried out on the impact of agronomic practices (water management, plant nutrition, and cultural practices) on tri-trophic interactions to optimize insect pest management in Southern row crops.
Progress Report
An eight-year examination of the susceptibilities of corn earworm (Helicoverpa zea) populations to a diamide insecticide, chlorantraniliprole, was completed. The diamide insecticides are currently the most commonly used class of insecticide to control damaging populations of caterpillar pests in the Southern United States. No visible shifts in the resistance frequency were detected using measurements via diet-incorporated bioassays. We have begun to track other measurements of fitness on these caterpillars to find more sensitive techniques for earlier detection of resistant individuals.
The population dynamics of corn earworm and tobacco budworm (Chloridea virescens) moths have been monitored weekly from May to September since 2008 using sex pheromone traps. Nine counties Five counties in Mississippi are monitored, and county averages are reported weekly to assist farmers in managing their crops for these pests. Increasing weekly populations alert farmers and consultants of the need to monitor fields closely. Efforts are underway to understand the impact of the local and regional crop landscape and other landscape factors on the quantity and timing of corn earworm and tobacco budworm moth catches using data collected over 10 years.
Nematodes are roundworms that have been used for insect control in some systems. They enter the insect and, release bacteria, and can complete the life cycle within their host. Five entomopathogenic (causing disease in insects) nematode strains were selected for field tests against corn earworm in corn silk and the soybean looper on soybean plants. The results indicated that all strains of one species, Steinernema carpocapsae, were the most effective in aboveground application for both corn earworm and soybean looper. Additionally, adjuvants (enhancers) were shown to increase the mortality and infection of these nematodes in newly hatched corn earworms in corn whorls. These experiments will be repeated and carried out again in the summer of 2024.
Although the use of nematodes in agriculture has gained significant traction in recent years as a pest management tool, little is known about its effects on beneficial insects and other tropic interactions. Lab bioassays of the ten most prevalent nematode isolates showed minimal to no mortality on the beneficial sculpted damsel bug (Nabis roseipennis), a common generalist predator. Greenhouse and lab studies indicated no cross-infectivity from predation events, and predators generally avoided infected prey. These findings demonstrate the environmental friendliness, target specificity, and efficacy of nematodes in sustainable pest management.
Rearing feral populations of insects in the laboratory is essential to conducting research related to the biology and ecology of these populations. Some of these colonies of insects are reared throughout the year, and the availability of a suitable food source that provides ample nutrition for these insects is challenging. Different combinations of host plants and food sources were examined to improve the rearing conditions of three important sucking insect pests: the tarnished plant bug (Lygus lineolaris), the southern green stink bug (Nezara viridula), and the brown stink bug (Euschistus servus). Improved combinations of food sources and inclusion of food sources that had longer feeding acceptability, such as potatoes, improved the health of these insects.
In Mississippi, the stink bug complex infesting soybean primarily includes the brown stink bug, southern green stink bug, green stink bug (Chinavia hilaris), and red banded stink bug (Piezodorus guildinii). We employed sprayed bioassays to evaluate the susceptibilities of these stink bugs to seven commonly used formulated insecticides. Enzyme activity analysis revealed no significant differences between the southern green and green stink bugs. However, some populations of brown stink bug and red banded stink bug exhibited elevated enzyme activities, indicating potential variations in resistance mechanisms. These findings provide a baseline for monitoring insecticide resistance in Pentatomidae and can guide insecticide resistance management strategies for Mississippi soybean.
The tarnished plant bug and redbanded stink bug pose significant economic threats to cotton and soybean crops in the mid-southern USA. Despite the low efficacy of insecticide spraying, adjuvants play a crucial role in optimizing insecticide performance. We evaluated the impact of two adjuvants on enhancing the efficacy of the insecticides bifenthrin and imidacloprid, through laboratory spray bioassays. Both adjuvants exhibited synergistic effects with technical-grade insecticides. High concentrations of polyacrylamide increased the efficacy of bifenthrin by 1.50- and 1.70-fold for tarnished plant bug and redbanded stink bug, respectively. Both adjuvants enhanced the effectiveness of imidacloprid in redbanded stink bug by up to 2.68- and 2.73-fold, respectively. This study highlights the synergistic impact of these adjuvants on the efficacy of technical grade and formulated bifenthrin and imidacloprid insecticides, providing valuable insights into optimizing pest control strategies in agriculture.
Combining visual cues (red color) with olfactory cues (pheromone blends) significantly increased the capture of tarnished plant bug in the field. Field experiments investigated the practical applications of using female-produced sex pheromone blends in combination with red or white sticky cards to monitor the overwintering tarnished plant bug populations in early spring. This is the first study that reports the use of red sticky card-based pheromone traps for early season monitoring of tarnished plant bug on wild hosts, and for tracking their movement between field edges and cotton. The results were published in the Insects journal.
Attract-and-kill strategy using pheromones and trap crops: An attract-and-kill strategy using pheromone traps in combination with or without trap crops (mustard) and different insecticide treatments were tested under field conditions. Preliminary field experiments showed that significantly higher number of tarnished plant bugs were attracted to trap crops containing pheromones than trap crops alone. A combination of red sticky card-pheromone blends with minimal insecticidal spray controlled plant bugs, and increased cotton yield. Y-tube olfactometer studies have identified s-linalool as an attractant for female tarnished plant bugs. Also, multiple potential repellants were screened in olfactometer (odor measuring device) assays for testing under field conditions.
Numerous insect pests attack sorghum in the southern United States. Key economic pests of sorghum include a recent invasive aphid and a complex of moths known collectively as headworms. Studies were conducted to assess the effectiveness of integrating multiple aphid pest management strategies and their combined impact on headworms and natural enemies in sorghum. Natural enemies are capable of suppressing both aphid and headworm densities and are essential for limiting the amount of insecticides applied to manage insect pests. Results indicated no negative effects of sorghum host plant resistance for aphids on natural enemies. The integration of insecticides and host plant resistance for aphids impacted the population dynamics of headworms and their natural enemies. Research is still ongoing to evaluate the impact of different combinations of management strategies for aphids and headworms on sorghum yield and economics.
Tarnished plant bugs are a key pest of cotton in the Midsouth region and some areas of the eastern United States. Its control methods have been solely based on chemical insecticides, which has contributed to insecticidal resistance and shortened residual periods for control of this insect pest. Additionally, the stink bug complex in soybean is controlled mainly with the use of synthetic insecticides. Naturally occurring populations of tarnished plant bug and the stink bugs on non-cultivated host plants are exposed to a range of natural control agents that include a combination of bacterial, fungal, parasitoids, and viral agents. Previously isolated agents from tarnished plant bug and the stink bugs collected from wild non-crop hosts have been characterized both by morphological and molecular methods to identify additional potential control agents. Fungal isolates have been tested at a diagnostic concentration on established laboratory colonies of tarnished plant bugs and stink bugs and compared to current research and commercially available strains. Spore powder of the most promising fungi will be produced in the laboratory using a biphasic culture system on a small-scale similar to other fungal spore production systems and evaluate their pathogenicity on field trials.
Endophytes are organisms that live between plant cells. Endophyte isolates from corn have shown insecticidal and larvicidal efficacy against corn earworm larvae and other key cotton insect pests, such as tarnished plant bug nymphs. Field evaluation in cotton has shown no adverse effects on seedling germination and growth when colonized by endophytic fungi. While minor differences in insect injury were detected across colonized cotton plants, no differences in yield were observed. We are exploring alternative seedling inoculation methods to enhance the practicality of this biological control strategy.
Accomplishments
1. Evaluation of biological and synthetic insecticides for sustainable insect control in cotton. The effects of synthetic and biological insecticides for control of two major insect pests of cotton in the Southern United States, tarnished plant bug and bollworm, were evaluated by ARS researchers in Stoneville, Mississippi. Biological insecticides successfully reduced pest insect densities in cotton. However, they were not as economically effective as control with conventional insecticides, which had the most significant positive impact on yield and net return above treatment costs for growers. This research demonstrated why conventional insecticides are featured heavily in current cotton pest management strategies, but environmentally beneficial alternatives are still needed to ensure sustainability.
Review Publications
Blanco, C., Hernandez, G., Conover, K., Portilla, M., Valentini, G., Alvarado, A., Fosado, A., Abel, C.A., Dively, G., Guzman, H., Israel, L., Occelli, L., Knolhoff, L., Corona, M., Vega, P., Macias, P., Ward, T., Urbano, N. 2024. Functional transgenes in Mexican maize: benefit and risks for insect pest management in Mexico and the United States. Annals of the Entomological Society of America. https://doi.org/10.1093/aesa/saae007.
Kiju, P., Wanner, K.W., Ivie, M., Mcphee, K., Reddy, G.V. 2024. Pea leaf weevil, Sitona lineatus (L.)(Coleoptera: Curculionidae), adult feeding preference and larval development on pulse crop varieties in Montana. Pest Management Science. 80:1-13. https://doi.org/10.1002/ps.7970.
George, J., Reddy, G.V., Wadl, P.A., Rutter, W.B., Culbreath, J.R., Lau, P.W., Rashid, T., Allan, M.C., Johanningsmeier, S.D., Nelson, A.M., Wang, M.L., Gubba, A., Ling, K., Meng, Y., Collins, D.J., Ponniah, S.K., Gowda, P.H. 2024. Sustainable Sweetpotato Production in the United States: Current Status, Challenges, and Opportunities. Agronomy Journal. 116(2):630-660. https://doi.org/10.1002/agj2.21539.
George, J., Glover, J.P., Reddy, G.V., Johnson, C.P., Hall, D.R. 2023. Early season monitoring of tarnished plant bug, Lygus lineolaris, in wild hosts using pheromone traps. Insects. https://www.mdpi.com/2075-4450/14/10/805.
Du, Y., Scheibener, S.A., Zhu, Y., Portilla, M., Zhang, M(2023)Resistance risk assessment of six pyrethroids and acephate toward the resistant adult tarnished plant bug, Lygus lineolaris (Palisot de Beauvois). Insect Science. https://doi.org/10.1111/1744-7917.13280.
Du, Y., Scheibener, S.A., Zhu, Y., Portilla, M., Reddy, G.V. 2023. Biochemical and molecular characterization of neonicotinoid resistance in the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois). Comparative Biochemistry and Physiology. https://doi.org/10.1016/j.cbpc.2023.109765.
Chen, X., George, J., Diepenbrock, L., Gossett, H., Liu, G., Quereshi, J., Stelinski, L. 2023. Feeding behavior and hormoligosis associated with imidacloprid resistance in Asian citrus psyllid, Diaphorina citri. Insect Science. https://doi.org/10.1111/1744-7917.13293.
Little, N., Elkins, B.H., Portilla, M., Allen, K.C., Read, Q.D., Paulk, R.T. 2024. Field evaluation of biological and conventional insecticides for managing multiple insect pests in cotton. Journal of Entomological Science. https://doi.org/10.18474/JES23-37.
Blanco, C., Conover, K., Dively, G., Hernandez, G., Portilla, M., Nava-Camberos, U., Abel, C.A., Williams, P., Hutchison, W. 2023. Severe Defoliation of Vegetative Maize Plants Does Not Reduce Grain Yield: Further Implications with Action Threshold. Southwestern Entomologist. https://doi.org/10.3958/059.048.0404.
Guerrero, A., Reddy, G.V. 2023. Chemical Communication in Insects: New Advances in Integrated Pest Management Strategies. Insects. 14:01-05. https://doi.org/10.3390/insects14100799.
Du, Y., Scheibener, S.A., George, J., Kannan, N., Portilla, M. 2024. Assessing the Efficacy of Sodium Alginate and Polyacrylamide as Spray Adjuvants Combined with Bifenthrin and Imidacloprid against Lygus lineolaris and Piezodorus guildinii. Agriculture. 14(4):535. https://doi.org/10.3390/agriculture14040535.
Du, Y., Scheibener, S.A., Zhu, Y., Allen, K.C., Reddy, G.V. 2024. Insecticide Susceptibilities and Enzyme Activities of Four Stink Bug Populations in Mississippi, USA. Insects. 15:265. https://doi.org/10.3390/insects15040265.
Elkins, B.H., Little, N., Johnson, C.P., Allen, K.C. 2024. Dynamics of Melanaphis sorghi1 and Its Natural Enemies in Johnsongrass and Grain Sorghum with Variable Levels of Host Plant Resistance. Southwestern Entomologist. 49(2):1-19. https://doi.org/10.3958/059.049.0209.
Zhang, M., Spaulding, N.R., Reddy, G.V., Shapiro Ilan, D.I. 2024. The efficacy of entomopathogenic nematodes plus an adjuvant against Helicoverpa zea and Chrysodeixis includens in aboveground applications. Journal of Nematology. 56(1):14. https://doi.org/10.2478/jofnem-2024-0018.