Location: Southern Insect Management Research
2021 Annual Report
Objectives
Objective 1: Determine key factors that naturally regulate tarnished plant bug (TPB) population increases and develop new tools for managing tarnished plant bug, including bio-control strategies.
Sub-objective 1.A. Quantify the impact of biological control on TPB seasonal abundance and distribution.
Sub-objective 1.B. Identify and develop new biological control options (including entomopathogens, entomophagous insects, host manipulation and behavioral modification) as possible regulators of TPB population growth.
Sub-objective 1.C. Identify sampling methods for TPB that are cost and time effective for landscape level monitoring, evaluate their use as tools in TPB population management, and link information about seasonal habitat changes to population dynamics.
Objective 2: Develop novel alternative ways to deploy tarnished plant bug control agents, and evaluate effectiveness of these deployment methods in large-scale field experiments.
Sub-objective 2. A. Determine if sprays of the NI8 strain of Beauverua (B.) bassiana applied alone and in combination with novaluron will suppress TPB populations colonizing adjacent cotton.
Sub-objective 2. B. Measure impacts of NI8 and new biological control agent identified in Sub-objective 1B on TPB populations infesting wild hosts and crops in the Mississippi Delta.
Approach
The key factors that naturally regulate tarnished plant bug (TPB) population will be determined by collecting feral population from wild host plants, and when available, in cultivated crops at different locations within the Mississippi Delta. TPB nymphs and adults will be collected at each location. Collected insects will be used for microbial and parasitoids identification, molecular identification studies, life table construction, and stable carbon isotope study. Potential entomopathogenic fungi will be bioassayed in replicated laboratory tests and compered with NI8. The most effective fungus will be tested in large-scale field experiments.
Progress Report
This report serves as a final report for this project, which was merged with the project 6066-22000-090-00D “Insect Control and Resistance Management in Corn, Cotton, Sorghum, Soybean, and Sweet Potato, and Alternative Approaches to Tarnished Plant Bug Control in the Southern United States”.
In cooperation with Crop. Defenders, Canada, we completed to screen twelve isolates of entomopathogenic fungi belonging to Metarhizium robertsii, M. pinghaense, M. brunneum, Beauveria bassiana and Isaria fumosorosea against adult tarnished plant bug (TPB). All isolates were pathogenic, causing mortality from 28.8 ± 3.4 to 96.3 ± 2.7%. The lethal time to 50% mortality (LT50) values ranged from 2.7 to 6.0-d while lethal time 90% mortality (LT90) values varied between 6.6-d and 15.0-d. M. robertsii isolate CPD6 was among the isolates that caused high mortality within shorter times and was selected for study on developmental stages and greenhouse trial. The 3rd, 4th and 5th instar nymphs, and adults were inoculated with 106, 107 and 108 conidia mL-1 of M. robertsii CPD6. All the stages were susceptible to fungal infection. However, 3rd and 4th instars were the most susceptible with no significant differences in mortality across the three concentrations. On the other hand, mortality was dose-dependent with 5th-instar nymph and adult stages. LT50 and LT90 values were also dose-dependent, with higher concentration having shorter lethal time values as compared to the lower concentrations. In the greenhouse, pepper plants were sprayed with CPD6 and chemical insecticide Flonicamid, before releasing adult TPB. Mortality of 37.3, 75.5 and 76.3% was recorded in the control, CPD6 and Flonicamid, respectively. The present study has identified M. robertsii CPD6 as potential mycoinsecticide candidate for the control of L. lineolaris. It has also demonstrated that younger stages are more susceptible to fungal infection than older stages, an important factor that should be considered when applying mycoinsecticide in the field.
We completed the first replication of two strains of Beauveria bassiana experiment to evaluate the effect of the native and commercial B. bassiana strains on the fecundity of the southern green stink bug, SGSB. The SGSB, Nezara viridula (L.) (Heteroptera: Pentatomidae), is one of the most important agricultural pests of soybean and cotton in North and South America. Two controls (water and Tween-80) and four concentrations (nx104, 105, 106, and 107) of two isolates of Beauveria bassiana Vuillemin (Hypocreales: Cordycipitaceae) including the commercial strain GHA and the Mississippi Delta native NI8 strain were evaluated in the laboratory to determine the effect on the fecundity of a laboratory colony of N. viridula. Both isolates of B. bassiana with the highest concentrations were pathogenic to the SGSB. However, females were much more susceptible to both strains than males. The measure lethal concentration (LC50) of the native strain NI8 was 1.4-fold lower (236 spores / mm2) than the commercial strain GHA (326 spores/mm2) for female scored 20-D after exposure. Much higher concentrations (11134963 spores/mm2, 5206971 spores/mm2) were required to kill males with both strains NI8 and GHA, respectively. High statistically significant differences were found in fecundity on couples sprayed with the highest concentration of GHA strain (nx107), while couples sprayed with the native NI8 (nx106 and 107) were significantly higher compared with both controls and the lower concentrations. Cumulative fecundity for controls and lower concentrations ranged from 1178 to 2082 eggs/10 couples/life reproduction, compared with 597 and 673 eggs/10 couples sprayed with NI8 nx106 and 107, respectively and 386 eggs/10 couples sprayed with GHA nx107. Further field testing is needed to evaluate the potential for in-field control.
A method for rearing the southern green stinkbug, Nezara viridula (L.) (Heteroptera: Pentatomidae), using the lygus semi-solid artificial diet was developed. Early nymphs (1st and 2nd instar) were reared in Petri-dishes (4 cm deep x 15 cm diam) in which were placed 15 egg masses (500 to 800 fertile eggs/ petri-dish). Later instar nymphs (3rd to 5th) and adults were reared in cages (43 x 28 x 9 cm), each holding about 500 nymphs or adults. Mating and oviposition occurred in oviposition cages (Popup Rearing Cages 30 x 30 cm), each holding 60-90 mixed sex adults of similar age. Adults emerged under these conditions 35.88 days after oviposition and survived for an average of 43.09 days. On average, adults laid 223.95 eggs in their lifetime, for a total production of 8,168 eggs / rearing cage. Egg fertility was 77.93%. Egg masses held in petri-dishes had a total hatchability of 79.38%. Mortality of early nymphs in petri-dishes was 0.64% for the first instar and 1.37% for second instar. Late nymphal mortality in rearing cages was 1.41, 3.47, and 4.72% for the 3rd, 4th, and 5th instars, respectively. Survivorship from nymphs to adults was 88.48%. Using artificial diet for rearing N. viridula reduced cost and increased reliability and simplicity of bug production, which should facilitate mass rearing of its biological control agents.
Codification and identification of the microbial agents from field samples collected in Mississippi Delta during 2016-2018 was completed. Spore powder of new microbial agents will be produced and used in bioassays to evaluate the pathogenicity on tarnished plant bugs and other pestiferous insects of southern crops and potential impact on beneficial insect populations.
Accomplishments
1. Efficacy of Beauveria bassiana and other biocontrol agents for control of the tarnished plant bug and other insect pests. Microbial insecticides are an important component of many insect pest management programs. ARS researchers in Stoneville, Mississippi, quantified the impact of the native strain NI8 on feral populations of tarnished plant bugs and its possible impact on beneficial arthropods. Continuation of laboratory and field experiments has determined mortalities and estimate lethal doses of potential microbial insecticides including the native Delta strain NI8 and the commercial strain GHA on feral tarnished plant bug populations and southern green stink bug on cotton and soybean were completed and prepared for publication. These studies will impact the development of non-chemical control methods used in cotton integrated pest management systems across the southern United States.
Review Publications
Achhami, B.B., Peterson, R.K., Sherman, J.D., Reddy, G.V., Weaver, D.K. 2020. Multiple decrement life tables of Cephus cinctus Norton (Hymenoptera: Cephidae) across a set of barley cultivars: The importance of plant defense versus cannibalism. PLoS ONE. 15(9):e0238527. https://doi.org/10.1371/journal.pone.0238527.
Rezaei, M., Talebi, A., Fathipour, Y., Karimzadeh, J., Mehrabadi, M., Reddy, G.V. 2020. Effects of cold storage on the life history traits of Aphidius matricariae. Entomologia Experimentalis et Applicata. 168(11):800-807. https://doi.org/10.1111/eea.12958.
Achhami, B.B., Reddy, G.V., Sherman, J.D., Peterson, R.K., Weaver, D.K. 2020. Antixenosis, antibiosis, and potential yield compensatory responses in barley cultivars exposed to wheat stem sawfly (Hymenoptera: Cephidae) under field conditions. Journal of Insect Science. 20(5):1-14. https://doi.org/10.1093/jisesa/ieaa091.
