Comparison of hydrogels to enhance the environmental tolerance of the entomopathogenic nematode, Steinernema carpocapsae (Weiser)

Authors: ELGAR, V - University Of Georgia; Shapiro Ilan, David; MOTA-SANCHES, DAVID - Michigan State University; WISE, JOHN - Michigan State University; BLAAUW,, BRETT - University Of Georgia

Submitted to: Journal of Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/12/2025
Publication Date: 7/14/2025
Citation: Elgar, V., Shapiro Ilan, D.I., Mota-Sanches, D., Wise, J., Blaauw,, B. 2025. Comparison of hydrogels to enhance the environmental tolerance of the entomopathogenic nematode, Steinernema carpocapsae (Weiser). Journal of Biological Control. 208. https://doi.org/10.1016/j.biocontrol.2025.105850.
DOI: https://doi.org/10.1016/j.biocontrol.2025.105850

Interpretive Summary: The lesser peachtree borer is a major wood-boring pest of peach trees and other stone fruit crops (such as cherries, plums nectarines). The insect bores into the trunk and scaffold limbs of stone fruit trees. Current management relies on broad-spectrum insecticides, which pose health and environmental risks, and have limited efficacy. Thus, alternatives are needed. Beneficial nematodes (also called entomopathogenic nematodes) are small round worms that are natural and environmentally safe bio-insecticides. Beneficial nematodes kill lesser peachtree borer but their efficacy is reduced by ultraviolet (UV) radiation and desiccation when applied aboveground. A protective gel formulation called "Barricade" enhances nematode efficacy and facilitates high levels of lesser peachtree borer control. However, lower cost formulations are desirable. A variety of alternative gel formulations were tested. i tool. Results indicate that sodium alginate and locust bean gum provide protection comparable to Barricade®. Therefore these new formulations can be tested on a wider scale for the ability to facilitate high levels of lesser peachtree borer control. The results may be applicable to other wood boring insect pests as well.

Technical Abstract: The lesser peachtree borer (LPTB; Synanthedon pictipes [Grote & Robinson]) is a major wood-boring pest of peach trees in the Southeastern U.S., requiring intensive management programs. The insect bores into the trunk and scaffold limbs of stone fruit trees. Current management relies on broad-spectrum insecticides like chlorpyrifos, which pose health and environmental risks, have limited efficacy, and are not organic-compliant. The entomopathogenic nematode (EPN) Steinernema carpocapsae (Weiser) shows promise as an alternative, but its effectiveness is reduced by ultraviolet (UV) radiation and desiccation when applied above ground. Prior research found that suspending EPNs in the fire-retardant gel Barricade® improves survival under UV exposure in lab and outdoor conditions. However, Barricade® is not organic-compliant, and is costly, limiting its practical use and posing barriers to adoption as a management tool. Several organic, food-safe, natural polymer-based gels have the potential to replicate Barricade’s® properties. This study evaluates whether sprayable natural hydrogels—sodium alginate, xanthan gum, carboxymethyl cellulose, and locust bean gum—can enhance EPN survival under UV and desiccation in lab and outdoor settings. Results indicate that sodium alginate and locust bean gum provide protection comparable to Barricade® in maintaining EPN viability and virulence after desiccation exposure. These findings support the use of natural hydrogels to improve EPN resilience to limiting factors in above-ground environments, promoting their use in sustainable pest management for peach pests. Future research should investigate field applications, including optimal treatment timing and gel degradation dynamics, to optimize natural gels for protecting EPNs in above-ground treatments targeting LPTB larvae or other wood boring insects.