Biocontrol with Benefits: Enhancing Sustainability by Adding Value

Implementation of a targeted biocontrol strategy that positively impacts other aspects of the orchard system (such as overall plant health and suppression of plant diseases/plant-parasitic nematodes) could be a powerful approach in establishing sustainable orchard practices. The  project built and expanded upon a previously funded Southern SARE grant focused on peach orchard systems. Peachtree borer, Synanthedon exitiosa, is a major pest of peaches and other stone fruit trees in the Southeast and throughout the USA. Currently, methods of control for peachtree borer focus on the use of broad spectrum chemical insecticides, primarily chlorpyrifos. Due to severe environmental and regulatory concerns alternative methods of control must be developed and their impact on cropping system assessed. In our previous research we discovered that the entomopathogenic nematode (aka beneficial nematode), Steinernema carpocapsae, can provide the same level of peachtree borer control as chemical insecticide standards such as chlorpyrifos. The nematodes can be applied effectively as preventative agents in the late summer or fall and in a curative approach during the spring, whereas chlorpyrifos is only effective in a preventative application. Despite this success, grower adoption in using nematodes for peachtree borer control has been limited due to a cost differential; entomopathogenic nematodes cost approximately $15 per acre ($37 per hectare), whereas chemicals like chlorpyrifos may cost as low as $5 to $10 per acre ($12 to $25 per hectare).

The use of entomopathogenic nematodes would be more attractive if the approach provided other benefits to the growers. Preliminary and prior research indicates that entomopathogenic nematodes targeting peachtree borer may also affect root-feeding weevils, plant-parasitic nematodes, and the devastating plant pathogenic fungus, Armillaria tabescens; thus, the goal of this project is to investigate additional benefits that entomopathogenic nematodes can provide against these important pest and disease challenges. If significant benefits are realized in controlling any or all of these targets (plant- parasitic nematodes, root-feeding weevils and pathogenic fungi) this will add substantially to the efficacy and attractiveness of biocontrol approach. Research was conducted using a multidisciplinary systems approach encompassing fields of entomology, plant pathology, nematology, horticulture and economics. The studies were in cooperation with large conventional peach farmers as well as an organic peach grower. We have strong grower support for the project, one of the largest peach growers in Georgia wrote, "I'd be happy to cooperate, collaborate, or even collude with you on this grant. I think you are on the right track exploring other possible benefits and look forward to working with you." 

Overall our results indicated clearly that applications of beneficial entomopathogenic nematodes consistently reduce peachtree borer populations as well or better than chemical insecticides. We observed that lower rates of nematodes could be used to control peachtree borer (as low as 300,000 nematodes per tree). Moreover, we observed additional benefits of beneficial nematode application including the control of root-feeding weevils in peach orchards. 

The purpose of this project is to facilitate the implementation of biocontrol in Southeastern peach insect pest management systems. Specifically, we will expedite the implementation of a biocontrol approach by leveraging additional benefits that may be garnered within the peach system. It is important to recognize that agricultural inputs do not act in isolation; interrelationships among biotic and abiotic agents abound. We will utilize these interrelationships to enhance sustainability.