Location: Southern Insect Management Research
2023 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 examination of the susceptibilities of corn earworm, Helicoverpa zea, populations to a diamide insecticide was continued. 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 insecticide resistance were detected. We continue to monitor this insect to the diamide insecticide class to provide early detection of potential resistance issues.
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. Five counties in the Delta of Mississippi and four counties in the Hill region 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. Although fluctuations occur, no recent changes in yearly trends have been documented.
Sprayed bioassays were used to examine resistance levels of tarnished plant bug to three classes of insecticide during different times of the year in the Mississippi Delta. The greatest increase in tolerance from spring to fall was observed with pyrethroid and neonicotinoid insecticides, suggesting its extensive use to control tarnished plant bugs during the year. A synergist study demonstrated that the P450 inhibitor, piperonyl butoxide (PBO), significantly increased the toxicity of pyrethroids and neonicotinoids against resistant tarnished plant bugs.
A field population of tarnished plant bugs that exhibited elevated levels of resistance to pyrethroid and neonicotinoid insecticides was reared in the laboratory without further exposure to the insecticides. After 36 generations, the resistance levels decreased and enzyme activities associated with detoxification of insecticides decreased similar to levels in a laboratory susceptible population. This indicates that resistance development was likely conferred by increased gene expression of these enzymes and that the fadeaway of the resistance may be caused by reversing the overexpression of these enzymes.
In a greenhouse experiment, we studied the interaction of oxygenated water (15 ppm and 30 ppm) and arbuscular mycorrhizal fungus (AMF) on the growth and yield parameters of cotton and the development of tarnished plant bug on these treated plants. Preliminary results showed that the oxygenated water and AMF can influence germination, stem length, root length, and plant growth characteristics. No differences were observed in the development of Lygus nymphs on these different oxygenated water and AMF treatments compared to control plants.
Applying oxygenated and ozonated water to improve plant nutrition, root health, crop production, and yield, and how it affects the pest biology and above and below ground tri-trophic interactions of major pests of cotton and soybean through greenhouse and field studies are being performed.
Arbuscular mycorrhizal fungus, Rhizophagus intraradices, and fungal endophytes were purchased and sub-cultured, and spores were produced in the lab for mortality bioassays and behavioral assays. Endophytes used were SPE-120 (Beauveria bassiana), TAMU-4 (Purpureocelium lilacinum), NI-8, JG-1 and Botanigard (B. bassiana). Mortality assays showed little mortality of tarnished plant bug using the endophytic fungus. This summer, these AMF and fungal endophytes will be studied in a greenhouse and field study to understand their host plant resistance characteristics, plant growth and yield parameters. Electrical penetration graph (EPG) recordings will be performed later in the fall using these plants with AMFs and endophytes.
Field experiments investigated the practical application of using female- produced sex pheromone blends of tarnished plant bug in combination with red or white sticky cards to monitor the overwintering populations in early spring. Field experiments demonstrated that the red sticky cards combined with Byers pheromone blend containing hexyl butyrate, (E)-2-hexenyl butyrate, and (E)-4-oxo-2-hexenal in 4:10:7 ratio are highly effective in trapping tarnished plant bug adults in early spring before row crops are planted. This is the first study that reports using red sticky card-based pheromone traps for early season monitoring of tarnished plant bugs on wild hosts and tracking their movement between field edges and cotton.
Ten strains of entomopathogenic nematodes (EPNs) were used to test against eggs, larvae, and pupae of corn earworms and soybean loopers in Petri dishes in the laboratory. Based on the laboratory results and availability of EPNs, Steinernema carpocapsae (All strain), and S. riobrave (7-12 strains) were used in the glasshouse and field with three different adjuvants, 0.125% dish soap, 0.125% dish soap combined with 0.25% vegetable oil, and 0.066% SAg Surfactant. In the glasshouse experiment conducted under sunny conditions and RH ranging from16%-72%, only the treatment involving Sr7-12 with dish soap combined with vegetable oil, along with a second round of water spraying, significantly increased the mortality of 5th instar of soybean looper, Chrysodeixis includens, compared to the Sr7-12 without adjuvants. However, under cloudy conditions and relative humidity (RH) ranging from 74% to 90%, no significant differences were observed when comparing ScAll with three adjuvant treatments with the ScAll suspension-only treatment. When examining the 1st instar of C. includens under mostly cloudy conditions with an RH ranging from 69% to 95%, there were no significant differences in mortalities and EPN infections compared to the control group. Furthermore, in the field experiments, three adjuvant treatments significantly increased the mortalities and EPN infections of Sr7-12 and ScAll on 1st instar H. zea in corn plant whorls. Additionally, both adjuvant treatments, dish soap combined with vegetable oil and SAg Surfactant, significantly increased the mortality and EPN infections of ScAll on the 5th instar of C. includens on soybean plants. Moreover, ScAll was found to be more effective on soybean plants than Sr7-12.
The pathogenic fungus Cordyceps militaris ((L.) Fr.) Vuill. (Hypocreales) a historically medicinal strain of Beauveria spp. has significant insecticidal efficacy on all larval stages of the Mid-South corn earworm and other key row crops pests, including the stink bug complex. This study identified detrimental effects on embryonic development with high rates of underdeveloped and non-developed embryos associated with stink bug fecundity after exposure to fungal agents.
Commercially available corn hybrids were screened for potential endophytic fungi. Non-transgenic cultivars yielded three morphologically distinct species of naturally occurring endophytic fungi that have been isolated, purified, and cultured. Preliminary lab data suggest two candidate endophytes having entomopathogenic properties on cotton bollworm larvae and other key cotton insect pests, such as tarnished plant bug nymphs, leading to markedly high rates of larval mortality for BT resistant populations. Field evaluation in transgenic and non-transgenic cotton is currently in progress.
A suite of over 15 Heliothine specific viruses has been identified, and an initial bioassay has been completed screening the efficacy of each against corn earworm, soybean looper, fall army worm, Spodoptera frugiperda, and the redbanded stink bug, Piezodorus guildinii. Initial lab data showed greater than 70% mortality at 7 days post treatment for many Heliothine species. Field evaluation of multiple formulations is currently in progress.
Nine populations of the southern green stink bug, Nezara viridula L. (Heteroptera: Pentatomidae) were used to evaluate the effect of two strains of Beauveria bassiana (Balsamo-Crivelli) Vuillemin (Hypocreales: Cordycipitaceae) on fecundity and female and male susceptibility using four concentrations (106, 107, 108, and 109 spores/g) of a native (NI8) and commercial (GHA) entomopathogenic fungi alongside a water-control. The cumulative oviposition and survival of the populations were used to calculate the demographic parameters of this insect. Net reproductive rates (Ro) on populations sprayed with NI8 calculated based on total offspring showed a dose-dependent effect (72.55, 85.50, 58.15, and 37,60 females/newborn female) compared with water-control (87.65). In populations sprayed with GHA, only the highest concentration (109) was lower than control (27.15). The calculated Ro values based on fertile eggs were much lower as it was expected, with 60.75, 61.45, 45.45, and 32.05 females/newborn females from lowest to highest concentrations of NI8 and 21.50 for GHA highest concentration compared with water-control (78.45). These results demonstrated that both native and commercial strains affected embryo development, decreasing the growth and reproductive rates of N. viridula populations.
We continue to grow varieties of sweet potatoes at the Alcorn State Experiment Station in Mound Bayou, Mississippi, for the national sweet potato variety trial. This summer, a field study is being conducted to investigate the effects of using AMFs and fungal endophytes in sweeetpotato host plant resistance towards foliage and tuber feeding insects. Data will be collected on the effect of arbuscular mycorrhizal fungus and endophytes on sweetpotato growth, yield, plant physiology, and pest resistance characteristics. This study will use two varieties of wireworm susceptible and semi-resistant sweetpotato cultivars to understand the interactions of AMFs and endophytes with these cultivars.
Accomplishments
1. Chromosome scale assembly of the tarnished plant bug. Chromosome scale assembly of the tarnished plant bug. The tarnished plant bug is an insect pest damaging many cultivated crops in North America. The availability of a high-quality chromosome-length genome of tarnished plant bug would provide a foundation for advancing research on this species by ARS researchers in Stoneville, Mississippi. Despite being a pest of several economically important crops grown in North America, there is a general paucity of research on the genetics of tarnished plant bug. The initial genome of tarnished plant bug assembled with paired-end nucleotide sequences generated with Illumina technology was scaffolded with Illumina HiseqX reads generated from a proximity ligated (HiC) library to obtain a high-quality genome assembly. The final assembly contained 3968 scaffolds longer than 1 kilobase pair (kbp) to yield a genome of 599.97 megabase pair (Mbp). The N50 of the tarnished plant bug genome assembly was 35.64 Mbp and 98.68% of the genome was assembled into 17 scaffolds larger than 1 Mbp. This high-quality genome with chromosome size scaffolds will facilitate the development of universal markers for mapping genomic loci associated with host selection, insecticidal resistance, and population genomic studies.
Review Publications
Hiroyoshi, S., Takayuki, M., Kohama, T., Reddy, G.V. 2023. Effects of ejaculate size on remating, attractiveness and oviposition in females of the sweetpotato weevil, Cylas formicarius. Entomologia Experimentalis et Applicata. 00:1–9. https://doi.org/10.1111/eea.13275.
Glover, J.P., Reddy, G.V., Portilla, M. 2023. Fitness and survival of Helicoverpa zea (Lepidoptera: Noctuidae) on five weedy host plants commonly found across the Mid-South. Florida Entomologist. 106(1):45-50. https://doi.org/10.1653/024.106.0107.
Geedi, R., Reddy, G.V. 2022. Recent advances and challenges in implementing IPM programs in the Indian subcontinent. Indian Journal of Entomology. 84:1-15. https://doi.org/10.55446/IJE.2022.807.
George, J., Reddy, G.V., Little, N., Arnold, S.E., Hall, D.R. 2023. Combining visual cues and pheromone blends for monitoring and management of the tarnished plant bug, Lygus lineolaris (Hemiptera: Miridae). Pest Management Science. 79:2163-2171. https://doi.org/10.1002/ps.7395.
Allen, K.C., Little, N., Perera, O.P. 2022. Susceptibilities of Helicoverpa zea (Lepidoptera: Noctuidae) populations from the Mississippi Delta to a diamide insecticide. Journal of Economic Entomology. 116(1):160–167. https://doi.org/10.1093/jee/toac180.
George, J., Kanissery, R., Bashyal, M., Tamayo, B., Stelinski, L.L. 2022. Survival and feeding behavior of Diaphorina citri (Hemiptera: Liviidae) adults on common cover crops in citrus. Agriculture. 12:2175. https://doi.org/10.3390/agriculture12122175.
Catchot, B., Gore, J., Krishnan, N., Jackson, R., Musser, F. 2022. Insecticide resistance monitoring of tarnished plant bug (Hemiptera: Miridae) populations in the Mid-Southern United States. Journal of Cotton Science. 26(1):31-39. https://doi.org/10.56454/HTUA7872.
Mann, R., Crow, W., Catchot, A., Gore, J., Cook, D., Towles, T. 2022. A dynamic threshold approach for tarnished plant bug (Hemiptera: miridae) management in the midsouthern U.S. cotton. Journal of Economic Entomology. 115(4):1164-1169. https://doi.org/10.1093/jee/toac062.
Smith, J., Crow, W., Catchot, A., Cook, D., Gore, J. 2023. Determination of cresidual control and concentration of chlorantraniliprole in soybean. Journal of Economic Entomology. 116(42):472-477. https://doi.org/10.1093/jee/toad021.
Portilla, M., Zhang, M., Glover, J.P., Johnson, C.P., Reddy, G.V. 2022. Lethal concentration and sporulation by contact and direct spray of the entomopathogenic fungus Beauveria bassiana on different stages of Nezara viridula (Heteroptera: Pentatomidae). The Journal of Fungi. https://doi.org/10.3390/jof8111164.
Portilla, M., Reddy, G.V., Terluliano, M. 2022. Effect of two strains of Beauveria bassiana on the Fecundity of Nezara viridula L. (Heteroptera: Pentatomidae). Microbiology Research. 13(3):514-522. https://doi.org/10.3390/microbiolres13030035.
Perera, O.P., Saha, S., Glover, J.P., Parys, K.A., Allen, K.C., Snejana, G., Kurtz, R., Reddy, G.V., Johnston, S.J., Daly, M., Swale, T. 2023. A Chromosome scale assembly of the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), genome. BMC Research Notes. https://doi.org/10.1186/s13104-023-06408-w.
Glover, J.P., Portilla, M., Allen, K.C., George, J., Parys, K.A., Reddy, G.V. 2022. Susceptibility of different life stages of kudzu bug Megacopta cribraria (F.) (Hemiptera: Plataspidae) to two different strains of Beauveria bassiana. Pathogens. 11:1-10. https://doi.org/10.3390/pathogens11091028.
Du, Y., Zhu, Y., Portilla, M., Zhang, M., Reddy, G.V. 2023. The mechanism of metabolic resistance to pyrethroids and neonicotinoids fade away without selection pressure in the tarnished plant bug Lygus Lineolaris. Pest Management Science. https://doi.org/10.1002/ps.7570.
Glover, J.P., Nufer, M., Perera, O.P., Portilla, M., George, J. 2023. Entomopathogenicity of ascmycete fungus Cordyceps militaris on the cotton bollworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae). The Journal of Fungi. https://doi.org/ 10.3390/jof9060614.
Huahua, S., Yoshiko, N., Du, Y., Zewen, L., Boris, Z.S., Ke, D. 2022. Characterization of two kdr mutations at predicted pyrethroid receptor site 2 in the sodium channel of Aedes aegypti and Nilaparvata lugens. Insect Biochemistry and Molecular Biology. https://doi.org/10.1016/j.ibmb.2022.103814.
