Location: Fruit and Tree Nut Research2022 Annual Report
Objective 1: Develop alternative control strategies for the pecan weevil based on enhanced production, formulation delivery, and efficacy of microbial control agents, as well as improved fundamental knowledge of entomopathogens: Subobjective 1a. Determine the efficacy of biocontrol agents in suppressing the pecan weevil. Subobjective 1b. Investigate the basic biology and ecology of biological control agents. Subobjective 1c. Investigate improved methods of nematode pheromone production. Objective 2: Develop control strategies for pecan aphids using banker plants, optimization of chlorosis-impeding plant bioregulators, and the use of microbial control agents: Subobjective 2a. Assessment of banker plants for control of pecan aphid spp. in orchards. Subobjective 2b. Optimize use of plant bioregulators to manage M. caryaefoliae injury. Subobjective 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, barriers, mating disruption and application of entomopathogenic nematodes: Subobjective 3a. Determine efficacy of reduced-risk insecticides against stink bugs. Subobjective 3b. Determine efficacy of physical and insecticidal barriers against peach pests. Subobjective 3c. Use mating disruption to manage sesiid borers. Subobjective 3d. Develop entomopathogenic nematodes for control of key peach pests.
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 efficacy through improved delivery and formulation. Additionally, pertinent basic studies on entomopathogen foraging dynamics and production technology 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) implement efficacious microbial control tactics. Suppression of key peach pests via reduced-risk insecticides, physical and insecticidal barriers, mating disruption, and application of entomopathogenic nematodes will be examined. Anticipated products from this research include novel alternative pest management tactics involving microbial biocontrol agents, mating disruption, 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.
This report serves to document progress of research conducted under the project, 6042-22000-024-00D. Novel strategies for controlling key pecan pests, such as pecan weevil, pecan aphids, etc. 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 contribute to pecan aphid control; moreover lower rates of Grandevo were recently found to be effective in controlling pecan weevil while conserving beneficial natural enemies, and thus growers have started to adopt the technology. Additionally, new research was initiated to determine the efficacy of beneficial insect-killing nematodes in controlling flatheaded borers and ambrosia beetles; initial laboratory virulence assays indicated that both important insect pests are highly susceptible to certain species of beneficial nematodes. The beneficial insect-killing nematodes also controlled key peach pests, plum curculio and peachtree borer, at high levels. Basic research on the behavior of beneficial insect-killing nematodes was also implemented by ARS scientists at Byron, Georgia. In behavioral studies, the nematodes were found to display “follow the leader” trail-following behavior. Understanding nematode behavior will assist in developing methods to improve biological pest control. Addition of nematode specialized pheromones to biocontrol applications increased pest control efficacy by enhancing nematode movement and infectivity against pecan weevil in a field trial. The pheromones were also found to enhance other microbiome components resulting in increased disease-suppressing organisms in the soil. An industry partner is now developing this patent-pending technology. The first field tests to confirm the pheromone technology were initiated. Additionally, new formulations are being developed to protect insect-killing nematodes and fungi from UV radiation and desiccation. 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. Crape myrtle banker plants interplanted with pecan are capable of providing an alternative aphid food source that attracts, arrests and allows reproduction of pecan aphid natural enemies in the orchard. Research shows that timing the presence of the alternative food source can be controlled by flaring it using pyrethroid insecticides. The plant bioregulator gibberellic acid is now used for black pecan aphid management but further research is assessing ways to optimize its efficacy against the target pest. The nearly season-long occurrence of pest stink bugs in orchards requires materials for control that reduces the risk to natural enemies. Early results show that numerous products can impact stink bugs and that the neonicotinoid thiamethoxam increases stink bug activity of most products. Another tactic to combat stink bugs involves using barriers to prevent the low-flying pests from entering crops. Mating disruption of sesiid borers attacking peach continues to be used by peach growers. Investigations are now focused on evaluating weak links in this control process. Trapping at different heights in orchards and trapping in orchards with missing trees will allow us to detect faults in current mating disruption strategies and enact corrective procedures.
1. Nanoparticle formulations enhance biopesticide efficacy. Environmentally friendly biopesticides, such as entomopathogenic (insect-killing) nematodes and fungi can control various economically important insect pests such as pecan weevil and peachtree borer. The efficacy of these biopesticides, however, can be limited due to sensitivity to ultraviolet radiation. Thus, it is critical to develop new formulations that protect the biopesticide organisms from environmental stress. ARS researchers at Byron Georgia and Israeli partners discovered that nanoparticle-based formulations protect biopesticides from ultraviolet radiation and thereby increase pest control efficacy. This technology can lead to improved sustainability in pest management practices. A patent application is being submitted based on the discovery.
2. A bacteria-based biopesticide controls pecan weevil at reduced rates. The pecan weevil is a major pest of pecans. The insect is usually controlled with chemical insecticides, but these insecticides may be harmful to humans and the environment, kill beneficial natural enemies such as lady beetles, and cause flaring of pecan aphids (another group of important pecan pests). ARS researchers at Byron Georgia discovered that low application rates of an environmentally safe biopesticide “Grandevo”, which is based on a naturally-occurring bacterium, caused equal levels of pecan weevil control compared with recommended chemical insecticides. Moreover, in field experiments, the biopesticide contributed to pecan aphid control and conserved beneficial natural enemies. Thus, the bacteria-based biopesticide is a viable eco-friendly tool for control of pecan weevil. Grower adoption has been initiated based on the findings of ARS (Byron, Georgia).
3. Monitoring the whereabouts of a new stink bug pest across orchard and non-crop habitats. The invasive brown marmorated stink bug is a key pest of various crops and thus it is important to understand the insect’s distribution and movement patterns. ARS researchers at Byron Georgia monitored the pest using a grid system of traps across a 400-acre area including pecan and peach orchards in addition to non-crop habitats. Nymphs and adults aggregated primarily in peach and adjacent woodlands followed by pecan. Aggregation levels were highest in July and August. Non-crop host plants play an important role maintaining brown marmorated stink bug populations and growers need to be aware of these sources of brown marmorated stink bugs.
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