Research Project: New Tools for Managing Key Pests of Pecan and Peach

Location: Fruit and Tree Nut Research

2019 Annual Report

Objectives
Objective 1: Develop alternative control strategies for the pecan weevil based on enhanced production, formulation delivery and efficacy of microbial control agents, and improved fundamental knowledge of natural enemies: Sub-objective 1a: determine the efficacy of biocontrol agents in suppressing the pecan weevil. Sub-objective1b: investigate the basic biology and ecology of biological control agents. Sub-objective1c: investigate improved methods of nematode production. Objective 2: Develop alternative control strategies for pecan aphids using banker plants, optimization of chlorosis-impeding plant bioregulators, and microbial control agents: Sub-objective 2a: assessment of banker plants for control of pecan aphid spp. in orchards. Sub-objective 2b: optimize orchard use of plant bioregulators to manage M. caryaefoliae injury. Sub-objective 2c: implement microbial control agents for pecan aphid management. Objective 3: Develop alternative control strategies for key peach pests (plum curculio, sesiid borers, and stink bugs) via reduced-risk insecticides, repellents, barriers, mating disruption, and application of entomopathogenic nematodes. Sub-objective 3a: control stink bugs with reduced-risk insecticides. Sub-objective 3b: assess repellants and barriers for management of peach pests. Sub-objective 3c: mating disruption to manage sesiids borers. Sub-objective 3d: develop entomopathogenic nematodes for control of key peach pests.

Approach
Pecan and peach are important horticultural crops that can suffer severe losses in yield due to insect damage. The overall goal of this project is to provide economically and environmentally sound pest management strategies for control of key insect pests of pecan and peach. Objectives include alternative control strategies for key pecan pests (pecan weevil and pecan aphids) and key peach pests (plum curculio, sesiid borers, and stink bugs). Suppression of pecan weevil will focus on developing microbial control tactics including integrated entomopathogen applications and enhanced entomopathogen persistence through the use of cover crops and improved delivery. Additionally, pertinent basic studies on entomopathogen infection dynamics and delivery will be addressed. Management strategies for pecan aphids will 1) optimize usage of chlorosis-impeding plant bioregulators against the black pecan aphid, 2) incorporate banker plants into orchards for pecan aphid management and 3) identify and implement efficacious microbial control tactics. Suppression of key peach pests via reduced-risk insecticides, repellents, barriers, mating disruption, and application of entomopathogenic nematodes will be examined. Anticipated products from this research include novel alternative pest management tactics involving biocontrol agents, plant bioregulators, or other innovative strategies, improved methods for production, formulation, and delivery of biocontrol agents, and the filling of key knowledge gaps in basic insect pest and natural enemy biology and ecology.

Progress Report
Novel strategies for controlling key pecan pests, such as pecan weevil and pecan aphids, using bio-insecticides were explored. New research was initiated to investigate the potential for endophytic insect-killing fungi (living inside the tree) to contribute to pecan pest control. The endophytic fungus suppressed pecan aphid populations in a greenhouse setting. Entomopathogenic (insect-killing) nematodes provide high levels of control to the peachtree borer (a major peach pest). Research was initiated to determine additional benefits of applying entomopathogenic nematodes in a peach system; specifically (in conjunction with grower trials) experiments were conducted to look at impact of entomopathogenic nematodes on plant parasitic nematodes and on root-feeding weevils. A novel mechanism to enhance biocontrol efficacy for control of pecan weevil and other insect pests was tested. Adding nematode pheromones to improve beneficial nematode movement and infectivity resulted in enhanced pecan weevil control in greenhouse tests. The research on nematode and fungal bio-pesticides contributes to the goal of developing alternative biological solutions for control of key pecan and peach pests. Research was continued that evaluates the efficacy of using gibberellic acid (GA3) applied to pecan foliage as part of a black pecan aphid management strategy. Replicated, large plot studies show that foliar application of GA3 mitigates the ability of the black pecan aphid to elicit chlorotic feeding injury on leaves. Results of this novel research are adapted and used by more commercial pecan growers each year. Continuing collaborative research on the southward-moving brown marmorated stink bug showed that predation and especially parasitism of brown marmorated stink bug eggs is much higher than reported in the northeastern U.S. Numerous native parasite species were documented to attack brown marmorated stink bug eggs. Research continues to show the efficacy of mating disruption against Sesiidae attacking peach. For the second year in a row, areawide mating disruption has been adopted by southeastern U.S. peach growers. During 2019, 3,500 acres of commercial peach are under mating disruption in the southeast as a result of this research.

Accomplishments
1. Improving natural insect pest control by using pheromones. Beneficial nematodes (small round worms) are environmentally-friendly bio-pesticides that attack and kill a wide variety of economically important insect pests such as pecan weevil and peachtree borer. The nematodes produce pheromones that impact their behavior. ARS researchers in Byron, Georgia, along with industry and university colleagues, discovered that these natural pheromones can be commercially produced and mixed with the nematodes to enhance the little worms’ dispersal and infection behavior. The novel mixture results in substantially higher levels of insect pest suppression.

2. Mating disruption is gaining traction with southeast peach growers. For the second consecutive year, peach growers continue to use areawide mating disruption to manage borers. Conventional control of the peachtree borer and lesser peachtree borer has been difficult due to changes in insecticide labelling and the very long season (up to nine months) over which these pests must be controlled. ARS researcher in Byron, Georgia, and a collaborator has demonstrated that an areawide mating disruption approach provides control of these pests. The success of the project has led to the adoption of mating disruption of these pests by southeastern peach growers. During 2018 and 2019, 3,500 acres of commercial peach are under mating disruption each year because of this research.

3. One tiny step for a nematode, one big step toward sustainable agriculture in space. An exciting collaboration has been funded between ARS researchers in Byron, Georgia, and industry partners to send beneficial nematodes (small round worms) into space to the International Space Station. The mission represents a look into the future where food crops will be grown in space. The goal is to develop environmentally friendly methods for space travel that are not harmful to humans. The experiment will test the movement and infection behavior of beneficial nematodes (also called entomopathogenic nematodes) that control a wide array of insect pests in agriculture. Nematodes are environmentally friendly alternatives to broad spectrum chemical insecticides and are also safe to humans and other nontarget organisms. The team will find out if the nematodes will be able to navigate through soil and infect insects. This will be the first biological control experiment in space.

Review Publications
Leite, L., Shapiro Ilan, D.I., Hazir, S. 2018. Survival of Steinernema feltiae in different formulation substrates: improved longevity in a mixture of gel and vermiculite. Biological Control. 126:192-197.
Cottrell, T.E., Shapiro Ilan, D.I., Horton, D.L. 2019. Laboratory assays against adult and larval sap beetles (Coleoptera: Nitidulidae) using entomopathogenic nematodes, microbial-based insecticides and synthetic insecticides. Journal of Entomological Science. 54:30-42.
Wu, S., Kaplan, F., Lewis, E., Alborn, H.T., Shapiro Ilan, D.I. 2018. Infected host macerate enhances entomopathogenic nematode dispersal and infectivity in a soil profile. Journal of Invertebrate Pathology. 159:141-144. https://doi.org/10.1016/j.jip.2018.10.007.
Hazir, S., Shapiro Ilan, D.I., Bock, C.H., Leite, L. 2018. Thermo-stability, dose effects and shelf-life of antifungal metabolite-containing supernatants produced by Xenorhabdus szentirmai. European Journal of Plant Pathology. 150(2):297-306. https://doi.org/10.1007/s10658-017-1277-7.
Mbata, G., Ivey, C., Shapiro Ilan, D.I. 2018. The potential for using entomopathogenic nematodes and fungi in the management of the maize weevil, Sitophilus zeamais (Motschulsky) (Coleoptera: Curculionidae). Biological Control. 125:39-43. https://doi.org/10.1016/j.biocontrol.2018.06.008.
Hofman, C.O., Kaplan, F., Stevens, G., Lewis, E., Wu, S., Alborn, H.T., Perret-Gentil, A., Shapiro Ilan, D.I. 2019. Pheromones act as boosters for entomopathogenic nematodes efficacy. Journal of Invertebrate Pathology. 164:38–42.
Willett, D.S., Alborn, H.T., Stelinski, L.L., Shapiro Ilan, D.I. 2018. Risk taking of educated nematodes. PLoS One. 13(10):e0205804. https://doi.org/10.1371/journal.pone.0205804.
Cottrell, T.E., Tillman, P.G. 2019. A physical barrier reduces capture of Euschistus servus (Hemiptera: Pentatomidae) in pheromone-baited traps near peach trees. Florida Entomologist. 102(1):281-283. https://doi.org/10.1653/024.102.0155.
Balusu, R., Cottrell, T.E., Talamas, E., Toews, M., Blaauw, B., Sial, A., Buntin, D., Vinson, E.L., Fadamiro, H., Tillman, P.G. 2019. New record of Trissolcus solocis (Hymenoptera: Scelionidae) parasitizing Halyomorpha halys (Hemiptera: Pentatomidae) in the United States of America. Biodiversity Data Journal. 7:e30124. https://doi.org/10.3897/BDJ.7.e30124.
Ni, X., Cottrell, T.E., Buntin, G., Li, X., Wang, W., Zhuang, H. 2019. Monitoring of brown stink bug (Hemiptera: Pentatomidae) population dynamics in corn to predict its abundance using weather data. Insect Science. 26:536-544.
Rodriguez-Saona, C., Nielsen, A., Shapiro Ilan, D.I., Tewari, S., Kyryczenko-Roth, V., Firbas, N., Leskey, T.C. 2019. Exploring an odor-baited “trap bush” approach to aggregate Plum curculio (Coleoptera: curculionidae) injury in blueberries. Insects. 10(4):113. https://doi.org/10.3390/insects10040113.
Tillman, P.G., Cottrell, T.E., Buntin, D. 2019. Potential of Melia azedarach L. as a host plant for Halyomorpha halys (Stal) (Hempitera: Pentatomidae). Florida Entomologist. 102(1):222-226. https://doi.org/10.1653/024.102.0136.
Tillman, P.G., Cottrell, T.E. 2019. Influence of pheromone-baited traps on stink bugs (Hemiptera: Pentatomidae) in cotton. Journal of Insect Science. 19(1):1-7. https://doi.org/10.1093/jisesa/iey140.
Cottrell, T.E., Reeves, B., Horton, D.L. 2019. Spinosyns cause Aedeagus eversion in Carpophilus spp. (Coleoptera: Nitidulidae). Journal of Economic Entomology. 112(4):1658-1664. https://doi.org/10.1093/jee/toz055.