Investigating the Inoculation of Peach with an Entomopathogenic Fungus as a Potential Biocontrol Tactic Against Tree Boring Pests

View the project final report

Commodities

• Fruits: peaches

Practices

• Pest Management: biological control, integrated pest management

The delicious peach is a foundational crop in the Southeastern United States, with deep cultural roots and major economic importance. In 2021, over 120,000 tons of peaches across South Carolina and Georgia were harvested, valued at more than $170 million. Despite this success, peach production is facing new challenges. The U.S. Environmental Protection Agency (EPA) recently restricted the use of chlorpyrifos, a broad-spectrum insecticide that growers have long relied on for the management of key insect pests. For many foliar pests, there are still alternative insecticides available. However, for borer pests like the lesser peachtree borer (LPTB), effective chemical options are lacking.

Adult moths seek out peach trees where the females will lay their eggs. The LPTB larvae bore into the wood of peach trees to feed, subsequently damaging vascular tissue, weakening branches and scaffolds, reducing tree vigor, and making trees more susceptible destructive pathogens. Over time, infestations can lead to significant yield losses by reducing fruit-bearing capacity and/or, in severe cases, killing entire trees. Because the larvae remain hidden inside the tree, LPTB is especially problematic because it is difficult to detect early, and once established, infestations are hard to control with conventional insecticides. With growing restrictions on insecticide use, LPTB poses a persistent and costly threat to southeastern peach production, challenging growers to find sustainable and effective management strategies.

One potential alternative management strategy is the use of fungi that naturally infect insects—known as entomopathogenic fungi—which have historically been explored for pest management in other systems. Unfortunately, these fungi can be difficult to use in the field because they are sensitive to environmental conditions, and their effectiveness is limited when pests live hidden inside the tree. However, new research is showing promise by using these fungi in a different way: as endophytes, or beneficial fungi that live inside the plant itself. This approach has already been tested in other crops like pecan, coffee, and cacao. Building on that progress, our study is working to establish the entomopathogenic fungus Beauveria bassiana as an endophyte in peach. If successful, this could provide growers with a safe, sustainable tool to help manage LPTB and protect their orchards for the long term.

This project investigated whether the beneficial entomopathogenic fungus B. bassiana can live inside peach seedlings as an endophyte and produce the insecticidal compound beauvericin (BEA) systemically within plant tissues. The goal was to determine if this endophytic relationship could improve sustainable options for insect pest management in peach fruit production.

We found that B. bassiana successfully colonized peach leaves, stems, and roots through both foliar spray and soil drench application methods, confirming that peach can host this fungus endophytically. However, BEA production within plant tissues was minimal and unlikely to provide direct systemic insect control. By contrast, foliar spray applications resulted in high levels of BEA on plant surfaces, especially leaves at two weeks post treatment with the fungus. Feeding bioassays with mealworms (Tenebrio molitor) confirmed that these surface residues can negatively impact insect survival, supporting the role of B. bassiana as a contact-based insect biocontrol agent in peach.

The ability of B. bassiana to establish inside peach plants still has important implications for integrated pest management (IPM). Endophytic B. bassiana in other crops has been shown to improve plant stress tolerance, growth, and disease resistance. While more research is required to test these possibilities in peaches, this work provides the foundation for exploring B. bassiana and other fungal entomopathogens as a sustainable, multifunctional tool in peach production.

1. Determine if B. bassiana can establish inside peach seedlings as an endophyte through foliar spray and soil drench applications with a fungal inoculum.
2. Quantify and compare production of the insecticidal compound beauvericin (BEA) on plant surfaces versus inside colonized tissues, using surface sterilization to distinguish external vs. internal presence.
3. Assess the functional potential of endophytic and epiphytic B. bassiana as a biocontrol strategy by conducting insect feeding bioassays with the model insect the yellow mealworm, Tenebrio molitor, to test whether fungal and mycotoxin presence impact insect survival.