The Effects of Adjuvants on Steinernema Carpocapsae Efficacy Against Chrysodeixis Includens and Suspension Stability

Zhang, Minling; Spaulding, Nathan R.; Reddy, Gadi V. P.; Shapiro-Ilan, David I.

doi:10.2478/jofnem-2025-0063

Abstract

Chrysodeixis includens is a major soybean pest in the southern United States and has developed resistance to many insecticides. Entomopathogenic nematodes (EPNs) are potential alternative control tools. Above ground EPN applications are limited by environmental stresses; thus, we evaluated adjuvants to improve the performance of Steinernema carpocapsae. Laboratory assays showed that Xanthan & Tween enhanced EPN efficacy at 24 hr post application across all four exposure durations, whereas Barricade did not improve efficacy at the 1 hr exposure compared with EPNs without adjuvants. At 72 hr post application, adjuvant treatments achieved >90% mortality beginning at the 4 hr exposure duration, whereas EPNs without adjuvants reached >90% only at 24 hr. Greenhouse trials indicated efficacy improvements with Xanthan & Tween under some conditions, whereas Barricade did not. Optimization tests demonstrated that adding Tween to Barricade significantly improved EPN performance. Both Xanthan & Tween and Barricade & Tween reduced nematode sedimentation. Overall, adjuvant enhanced formulations increased EPN efficacy and stability, supporting their potential as a biological management tool for C. includens.

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The Effects of Adjuvants on Steinernema Carpocapsae Efficacy Against Chrysodeixis Includens and Suspension Stability

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