Location: Southern Insect Management Research
2025 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
Under Objective 1, a five-year examination of the susceptibilities of corn earworm (Helicoverpa zea) populations to a diamide insecticide, chlorantraniliprole, was completed. Diamide insecticides are currently the most widely used class of insecticide to control damaging populations of caterpillar pests in the Southern U.S. No visible shifts in resistance frequency were detected using measurements from diet-incorporated bioassays. We have begun to track other variables in these caterpillars to find more sensitive techniques for earlier detection of resistant individuals.
Spray bioassays were used to examine resistance levels of tarnished plant bugs (TPB) (Lygus lineolaris) to three classes of insecticides (neonicotinoids, organophosphates, and pyrethroids) collected during different times of the year in the Mississippi Delta. The most significant increase in tolerance from spring to fall collections was observed with pyrethroid and neonicotinoid insecticides. A subsequent study demonstrated that piperonyl butoxide, which inhibits P450 enzymes that detoxify insecticides, significantly increased the toxicity of pyrethroids and neonicotinoids against resistant TPB.
A field population of TPB that exhibited elevated levels of resistance to pyrethroids and neonicotinoids was reared in the laboratory without further exposure to these insecticides. After 36 generations, the resistance levels decreased, and enzyme activities associated with the detoxification of insecticides decreased to levels comparable to those in a laboratory-susceptible population. This suggests that resistance development was likely, at least in part, conferred by increased gene expression of these enzymes, and that the fading of the resistance may be caused by reversing the overexpression of these enzymes.
Under Objective 2,ARS researchers at Stoneville, Mississippi investigated the effects of applying water with extremely tiny, oxygenated bubbles (nanobubble water) and arbuscular mycorrhizal fungus (AMF) at different concentrations and combinations on cotton plants. This study revealed that nanobubbles and AMF have a positive impact on the plant's overall health in isolation and collectively. We also found that the survival rate of herbivorous insect pests was higher when they were reared on treated plants compared to control plants. Based on these findings, we conclude that the combination of nanobubbles and AMF can accelerate plant growth, indicating its potential use in sustainable crop production.
The effect of fungal endophytes on plant growth parameters and cotton yield was evaluated at various stages of plant development. The potential of these endophytes to cause disease in tarnished plant bug (TPB) (Lygus lineolaris) adults was studied in bioassays. The behavior of adult males and females toward cotton squares from these plants was analyzed using olfactometer (odor) assays. Experiments demonstrated that fungal endophytes colonized the structures of cotton plants, resulting in increased numbers of cotton squares, plant height, and weight compared to control plants. Beauveria bassiana strains showed significant mortality in TPB adults compared to controls. Also, male and female TPB adults exhibited repellent behavior towards cotton squares containing the JG-1 isolate of B. bassiana.
Under Objective 3, nematodes, also known as roundworms, have been used for insect control in specific systems. They enter the insect and release bacteria, and their life cycle is within the host. Five nematode strains that can cause insect mortality were selected for field trials targeting corn earworm (Helicoverpa zea) in corn silk and soybean looper (Chrysodeixis includens) on soybean plants. The Steinernema carpocapsae species was the most effective in above-ground applications 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.
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. Results indicated that sorghum host plant resistance to aphids had no adverse effects on natural enemies. The integration of insecticides and host plant resistance for aphids impacted the population dynamics of headworms and their natural enemies.
The annual National Sweetpotato Collaborator Group Trial was conducted at the Alcorn State University Farm in Mound Bayou, Mississippi. Entries in the trial included new and older varieties from Louisiana, the USDA, and North Carolina State University. All plots were evaluated for yield, and weekly insect collection data were analyzed to assess potential insect damage. Beauregard emerged as the top performer, yielding 560 bushels per acre. These results provide valuable insight into varietal performance, helping inform future cultivation and breeding efforts.
Under Objective 4, the red-banded stink bug (Piezodorus guidinii) and soybean looper (Chrysodeixis includens) are two of the most economically important pests of soybean in the Southern U.S. The tarnished plant bug (Lygus lineolaris) is a pest of several economically important crops grown in North America. High-quality genomes were sequenced and assembled for each of these three crop pests. This data will help advance the development of new control and monitoring methods for each insect.
Under Objective 5, two isolates of the fungus Beauveria bassiana were evaluated in the laboratory to determine the effect on the egg production of a laboratory colony of the southern green stink bug (SGSB) (Nezara viridula). Both isolates of B. bassiana at the highest concentrations were pathogenic to the SGSB. However, females were much more susceptible to both strains than males.
The same isolates of B. bassiana were used to evaluate survival, mortality, and molting percentage. Mortality and sporulation were positively correlated with concentration, while molting was highly variable. Adults of SGSB were highly resistant compared to the other life stages tested when exposed to contact or direct spray.
Under Objective 6, reliable pheromone-based traps are not currently available for use in monitoring populations of the tarnished plant bug (TPB) (Lygus lineolaris). Several experiments were conducted with visual and olfactory cues to determine their effectiveness in attracting TPB. It was found that the Byers blend, coupled with red sticky cards, significantly increased the capture of TPB in the field. This device, or a future iteration based on these findings, may contribute to sustainable and early-season monitoring and management of TPB in the field.
The pheromone blend-red sticky card trap was further tested in combination with trap crops to attract the TPB to the less expensive mustard trap crop before killing them with insecticides. Our two years of field data showed that a combination of pheromones with trap crops attracted significantly more TPB to the trap crops and reduced the plant bug damage in nearby cotton rows. Additionally, yields were similar between cotton plots receiving recommended insecticide applications and plots with trap crops, pheromones, and minimal insecticidal applications.
Adult populations of the corn earworm (Helicoverpa zea) and tobacco budworm (Chloridea virescens) have been monitored weekly in five counties in Mississippi from May to September since 2008 using sex pheromone traps. Average trap captures are reported weekly to help farmers manage their crops for these pests. Efforts are underway to understand the impact of the local and regional crop landscape, as well as other landscape factors, on the quantity and timing of corn earworm and tobacco budworm moth catches, using data collected over 10 years.
Accomplishments
1. Detection of a novel mutation that contributes to pyrethroid resistance in the tarnished plant bug. The tarnished plant bug (TPB) is one of the most serious pests threatening cotton crops in the Southern United States. Over time, heavy use of a common type of insecticide for their control, called pyrethroids, has caused many TPB populations to develop resistance, making these chemicals less effective. This resistance is linked to changes in the bug’s nervous system, the voltage-gated sodium channel, which helps send signals particularly through nerve cells. Pyrethroids work by targeting this channel, but through genetic testing, researchers discovered a specific mutation (called L1014S) in some TPB collected from cotton fields, which alters the sodium channel and makes the insect less susceptible to the pesticide. The findings show that TPB’s resistance comes not only from this mutation, but also from its ability to break down chemicals more efficiently. Notably, this is the first study to report the L1014S mutation in TPBs, adding an essential piece to the puzzle of how resistance develops.
2. Development of an improved method to rear a parasitoid of the southern green stink bug. The southern green stink bug (SGSB) is a significant pest of multiple crops, especially soybeans in the Southern U.S. It feeds on developing soybean seeds, impacting seed weight and quality. A parasitoid of eggs of the SGSB, Trissolcus basalis, is essential for the biological control of various stink bug species throughout the world. Scientists at Stoneville, MS, developed an improved method for rearing T. basalis by enhancing the production and storage of SGSB egg masses. This method will facilitate the mass release of this parasitoid for the control of the SGSB on soybeans and other essential field crops.
Review Publications
Phan, N.T., Biddinger, D.J., Rajotte, E.G., Smagghe, G., Reddy, G.V., Ren, Z., Joshi, N.K. 2024. Pesticide use in integrated pest and pollinator management framework to protect pollinator health. Pest Management Science. 80:1-6. https://doi.org/10.1002/ps.8582.
Fujii, T., Reddy, G.V., Kuriwada, T. 2024. Interspecific competition leads to more long-winged morphs in two sympatric cricket species. Ecological Entomology. 47:1-12. https://doi.org/10.1111/een.13391.
Debnath, R., George, J., Gautam, M., Shafi, I., Kariyat, R., Reddy, G.V. 2024. Ecological interactions, host plant defenses, and control strategies in managing soybean looper, Chrysodeixis includens (Lepidoptera: Noctuidae). Frontiers in Insect Science. 4:1-16. https://doi.org/10.3389/finsc.2024.1480940.
Pham, T.H., N.T. Phan, D.D.Trinh, H.N.Duong, P.T. Tran, K.D. Nguyen, G.V.P.Reddy, C.Jung,and N.K.Joshi. 2024. Comparative toxicities of commonly used agricultural insecticides to four honey bee species (Hymenoptera: Apidae) in Vietnam. Environmental Toxicology and Pharmacology. 113. https://doi.org/10.1016/j.etap.2024.104605.
Ayala, J., Gautam, M., Piessel, A., George, J., Kariyat, R. 2025. Pulsating drought and insect herbivory cause differential effects on Soybean (Glycine max) genotypes that vary in canopy wilting speed.. Plant-Environment Interactions. https://doi.org/10.1002/pei3.70028.
Allen, K.C., Elkins, B.H., Little, N. 2025. Environmental factors impacting leg coloration in Chrysodeixis includens. Environmental Entomology. 54(3):565-573. https://doi.org/10.1093/ee/nvaf031.
Hiroyoshi, S., Mitsunaga, T., Reddy, G.V. 2025. Effects of successful or unsuccessful parasitism by the solitary endoparasitoid wasp Cotesia vestalis (Haliday) (Hymenoptera: Braconidae) on the testis development in several host moth species. Journal of Insect Physiology. 163(06):1-8. https://doi.org/10.1016/j.jinsphys.2025.104808.
Portilla, M., Little, N., Allen, K.C., Zhu, Y. 2024. Effectiveness and residual activity of four common insecticides used in the Mississippi Delta to Control Tarnished Plant Bugs in Cotton. PLOS ONE. 19(6)01-20. https://doi.org/10.1371/journal.pone.0290858.
Okosun, O., George, J., Portilla, M., Glover, J.P., Parys, K.A., Reddy, G.V. 2024. Biology, Ecology, and Management of Redbanded Stink Bug, Piezodorus guildinii. Journal of Integrated Pest Management. 15(1):27. https://doi.org/10.1093/jipm/pmae019.
Gandham, K., Gautam, M., George, J., Reddy, G.V., Kariyat, R. 2024. Muffled olfactory and sensory cues from the reproductive stage soybean selectively reduce oviposition of a major polyphagous herbivore, fall armyworm (Spodoptera frugiperda). Pest Management Science. 81:01-11. https://doi.org/10.1002/ps.8600.
Ayala, J., Vasquez, A., Balakrishnan, D., Madrigal, E., George, J., Kariyat, R. 2024. Effects of fast and slow wilting soybean genotypes on fall armyworm (Spodoptera frugiperda) growth and development. Communicative and Integrative Biology. 17. https://doi.org/10.1080/19420889.2024.2354421.
Portilla, M., Tertuliano, M., Parys, K.A., Reddy, G.V., Glover, J.P. 2024. Effects of Beauveria bassiana on the growth and reproductive rates of Nezara viridula. BioControl. https://doi.org/10.1007/s10526-024-10258-1.
Anderson, S.E., Phan, N.T., Mcarthur, J.M., Reddy, G.V., Joshi, N.K. 2024. Arthropod Diversity Varies with Distance from On-Farm Floral Enhancements at Small Spatial Scales. Journal of Entomological Science. 59(3):1-6. https://doi.org/10.18474/JES24-39.
Erumal, V., Kannan, S., Alford, L., Pittarate, S., Mekchay, S., Reddy, G.V., Elangovan, D., Marimuthu, R., Krutmuang, K. 2023. Biocontrol effect of entomopathogenic fungi Metarhizium anisopliae ethyl acetate-derived chemical molecules: an eco-friendly anti-malarial drug and insecticide. Archives of Insect Biochemistry and Physiology. https://doi.org/10.1002/arch.22037.
Glover, J.P., Parys, K.A., George, J., Little, N., Portilla, M. 2024. Evaluation and Efficacy of Oral Biomarkers for Lygus Lineolaris1. Southwestern Entomologist. 49(2):713-732. https://doi.org/10.3958/059.049.0216.
Du, Y., Zhu, Y., Portilla, M. 2023. Assessment of the toxicity of four formulated pyrethroid-containing binary insecticides in susceptible and resistant adult tarnished plant bug, Lygus Lineolaris. Insects. https://doi.org/10.3390/insects14090761.