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

Location: Fruit and Tree Nut Research

2020 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
This final report serves to document progress of research conducted under the project, 6042-22000-023-00D. Novel strategies for controlling key pecan pests, such as pecan weevil and pecan aphids, using bio-insecticides were explored. An environmentally-friendly bio-insecticide “Grandevo” was found to control pecan weevil at levels equal to standard chemical insecticides and growers have started to adopt the technology. In new research, an endophytic insect-killing fungus (living inside the tree) was introduced into pecan trees for the first time. The endophytic fungus suppressed pecan aphid populations in a greenhouse setting and will be explored for control of aphid populations and other pests under field conditions. Basic research on the behavior of beneficial insect-killing nematodes and their mass-production technology was implemented. Improved diet media for mass production of beneficial nematodes using fermentation technology was developed. In behavioral studies, the nematodes were found to continuously travel in groups like a pack of wolves seeking their insect prey. Addition of nematode specialized pheromones to biocontrol applications increased pest control efficacy by enhancing nematode movement and infectivity; an industry partner is now developing this patented technology. Entomopathogenic (insect-killing) nematodes were discovered to provide high levels of control to the peachtree borer (a major peach pest). In prophylactic and curative applications the beneficial nematodes provided equal levels of control compared with chlorpyrifos. 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 and has led to adoption by growers and industry. Pecan aphid research has developed the plant growth hormone gibberellic acid (GA3) as a non-insecticidal management strategy for controlling the black pecan aphid that is being used by pecan growers. Pretreatment of pecan foliage with GA3 mitigates the ability of the black pecan aphid to elicit enzymatic breakdown of chlorophyll when feeding. Orchard trials have determined effective rates, frequency of application and residual activity. Research using crape myrtle as banker plants in pecan orchards for aphid management has worked out how to manipulate crape myrtle aphids populations on the banker plant. This manipulation allows us to increase natural enemy populations that will move to pecan to feed on pecan aphids. Research has determined efficacy of insecticides labelled for use on pecan at controlling stink bugs. Additionally, the concept of using a physical barrier to deter stink bug movement to a crop has been proven. Knowing the efficacy of various insecticides to stink bugs is important and the ability to use a physical barrier to manipulate stink bug movement will be further explored. Mating disruption for management of sesiid borers attacking peach has led to the adoption of this management practice by southeastern peach growers. Replicated studies never used plots that were large enough to exceed the flight ability of this pest and thus always failed. A demonstration trial incorporating approximately 1,000 acres of peaches in a 20 square mile area did surpass the flight ability of these pests and brought these orchard-killing pests under control.

Accomplishments
1. Pecan growers turning to gibberellic acid for black pecan aphid management. The black pecan aphid breaks down leaf chlorophyll for needed nutrients. This leaf injury negatively impacts accumulation of energy reserves by the pecan tree for the next crop and leads to premature leaf drop. ARS researchers at Byron, Georgia, have discovered that pretreatment of pecan foliage with gibberellic acid mitigates the enzymatic degradation of leaf chlorophyll by the black pecan aphid. During 2019, enough gibberellic acid was sold in Georgia to cover approximately 10,000 acres of pecan.

2. A friendly fungus living in the tree provides protection to pecan trees. Certain beneficial insect-killing fungi are used as natural bio-insecticides. These fungi are produced commercially and can kill a wide variety of important insect pests including pecan weevil and pecan aphids. However, the fungus can be costly to apply. ARS researchers at Byron, Georgia, discovered that the fungus can be introduced into the pecan tree as an endophyte (living inside the tree). As an endophyte the fungus provides built-in protection to the tree. Initial studies indicate the endophytic pecan trees have potential to suppress aphid populations and other pests. This technology could be used as an efficient and environmentally-friendly approach to control pecan pests.

3. Beneficial nematodes complete their first trip to space. In an exciting collaboration between ARS researchers at Byron, Georgia, and industry partners beneficial insect-killing nematodes (small round worms) were sent into space to the International Space Station. The goal was to develop environmentally friendly methods for space travel. Beneficial nematodes (also called entomopathogenic nematodes) are alternatives to broad spectrum chemical insecticides and are also safe to humans and other non-target organisms; they are used to control a wide variety of insect pests on Earth. The nematodes sent into space were capable of navigating through soil and killing insect pests. This was the first biological control experiment in space. The mission represents a look into the future where food crops will be grown in space.

Review Publications
Shapiro Ilan, D.I., Hazir, S., Glazer, I. 2019. Advances in use of entomopathogenic nematodes in IPM, In: Integrated management of insect pests: Current and future developments. Book Chapter. 649 – 678.
Ramakuwela, T., Hatting, J., Bock, C.H., Vega, F.E., Wells, L., Mbata, G.N., Shapiro Ilan, D.I. 2019. Establishment of Beauveria bassiana as a fungal endophyte in pecan (Carya illinoinensis) seedlings and its virulence against pecan insect pests. Biological Control. https://doi.org/10.1016/j.biocontrol.2019.104102.
Perret-Gentil, A., Shapiro Ilan, D.I., Sun, J., Mirti, A., Sampson, E.M., Schiller, K.C., Lewis, E., Kaplan, F. 2020. Conspecific and heterospecific pheromones stimulate dispersal of entomopathogenic nematodes during quiescence. Scientific Reports. https://doi.org/10.1038/s41598-020-62817-y.
Shapiro Ilan, D.I., Kaplan, F., Hofman, C.O., Schliekelman, P., Alborn, H.T., Lewis, E. 2019. Conspecific pheromone extracts enhance entomopathogenic infectivity. Journal of Nematology. (51)1-5. https://doi.org/10.21307/jofnem-2019-082.
Sandhi, R.K., Shapiro Ilan, D.I., Sharma, A., Reddy, G.V. 2020. Efficacy of entomopathogenic nematodes against the sugarbeet wireworm, Limonius californicus (Mannerheim) (Coleoptera: Elateridae). Biological Control. 143. https://doi.org/10.1016/j.biocontrol.2020.104190.
Sun, B., Li, F., He, X., Cao, F., Bandason, E., Shapiro Ilan, D.I., Ruan, W., Wu, S. 2020. First report of Ovomermis sinensis (Nematoda: Mermithidae) parasitizing fall armyworm Spodoptera frugiperda (Lepidoptera: Noctuidae) in China. Journal of Nematology. (52):1-7. https://doi.org/10.21307/jofnem-2020-050.
Koppenhofer, A.M., Shapiro Ilan, D.I., Hiltpold, I. 2020. Advances in the use of entomopathogenic nematodes (EPNs) as biopesticides in suppressing crop insect pests. Biopesticides for Sustainable Agriculture. (10)1-38. https://doi.org/10.19103/AS.2020.0073.10.
Pinero, J.C., Shapiro Ilan, D.I., Cooley, D.R., Tuttle, A., Eaton, A., Drohan, P., Leahy, K., Zhang, A., Hancock, T., Wallingford, A.K., Leskey, T.C. 2020. Toward the integration of an attract-and-kill approach with entomopathogenic nematodes to control multiple life stages of plum curculio (Coleoptera: Curculionidae). Insects. https://doi.org/10.3390/insects11060375.
Chen, C., Ma, H., Zheng, S., Ma, M., Li, J., Wu, F., Zhou, T., Gu, Xinhui, Gao, Yubao, Shapiro Ilan, D.I., Ruan, Weibin 2020. An innovative strategy for control of fungus gnats using entomopathogenic nematodes alone or in combination with waterlogging. Journal of Nematology. 52:1-9. https://doi.org/10.21307/jofnem-2020-052.
Acebes-Doria, A.L., Agnello, A.M., Alston, D.G., Andrews, H., Beers, E.H., Bergh, J., Bessin, R., Blaauw, B.R., Buntin, G., Burkness, E.C., Chen, S., Cottrell, T.E., Daane, K.M., Fann, L.E., Fleischer, S.J., Guedot, C., Gut, L.J., Hamilton, G.C., Hilton, R., Hoelmer, K.A., Hutchison, W.D., Jentsch, P., Krawczyk, G., Kuhar, T.P., Lee, J.C., Milnes, J.M., Nielsen, A.L., Patel, D.K., Short, B.D., Sial, A.A., Spears, L.R., Tatman, K.M., Toews, M.D., Walgenbach, J.D., Welty, C., Wiman, N.G., Van Zoeren, J., Leskey, T.C. 2019. Season-long monitoring of the brown marmorated stink bug (Hemiptera: Pentatomidae) throughout the United States using commercially available traps and lures. Journal of Economic Entomology. 113(1):159-171. https://doi.org/10.1093/jee/toz240.
Tillman, P.G., Toews, M., Blaauw, B., Sial, A., Cottrell, T.E., Talamas, E., Buntin, D., Joseph, S., Balusu, R., Fadamiro, H., Lahiri, S., Patel, D. 2020. Parasitism and predation of sentinel eggs of the invasive brown marmorated stink bug, Halyomorpha halys (Hemiptera: Pentatomidae) in the southeastern US. Biological Control. 145(2020)104247. https://doi.org/10.1016/j.biocontrol.2020.104247.
Balusu, R., Talamas, E., Cottrell, T.E., Toews, M., Blaauw, B., Sial, A., Buntin, D., Fadamiro, H., Tillman, P.G. 2019. First record of Trissolcus basalis (Hymenoptera: Scelionidae) parasitizing Halyomorpha halys (Hemiptera: Pentatomidae) in the United States. Biodiversity Data Journal. https://doi.org/10.3897/BDJ.7.e39247.
Tillman, P.G., Cottrell, T.E. 2019. Comparison of two insect-collecting devices for trapping stink bugs (Hemiptera: Pentatomidae). Journal of Entomological Science. 54(4):409-416. https://doi.org/10.18474/JES18-131.
Penca, C., Hodges, A.C., Leppla, N.C., Cottrell, T.E. 2020. Trap-based economic injury levels and thresholds for euschistus servus (Hemiptera: Pentatomidae) in Florida peach orchards. Journal of Economic Entomology. 133 (3):1347-1355. https://doi.org/10.1093/jee/toaa044.
Cottrell, T.E., Aiken, M.J., Thoms, E.M., Phillips, T. 2020. Efficacy of sulfuryl fluoride against fourth-instar pecan weevil (Coleoptera: Curculionidae) in pecans for quarantine security. Journal of Economic Entomology. 113(3):1152-1157. https://doi.org/10.1093/jee/toaa021.