How effective are entomopathogenic nematodes for vine weevil (Coleoptera: Curculionidae) biological control? A...

Vine weevil (Otiorhynchus sulcatus) is a globally important pest of soft fruit and ornamental crops with larvae causing significant root damage. Entomopathogenic nematodes (EPNs) have emerged as a key biological control option for larvae following restrictions on synthetic chemical insecticides, but their reported efficacy varies considerably across studies. This variability has created uncertainty about EPN effectiveness and optimal deployment strategies, limiting evidence-based recommendations for growers.

Across 162 comparisons from 23 studies, EPN applications significantly reduced vine weevil larval survival compared to untreated controls (Hedges' g = -1.60, 95% CI -1.85 to -1.36), equivalent to ≈63% fewer live larvae. All five EPN species tested (Steinernema carpocapsae, S. feltiae, S. kraussei, Heterorhabditis bacteriophora, H. megidis) were effective, with no significant differences among species. However, between-study heterogeneity was high (I² ≈ 97%), indicating variability in outcomes despite strong average benefits. Univariate analyses identified soil temperature as the strongest moderator, with warmer temperatures (18-30 °C) associated with greater EPN efficacy. Protected cropping environments (glasshouses) also enhanced performance compared to outdoor applications. Application method (drench versus drip irrigation) and growing medium type showed no significant effects. However, when accounting for clustering of effects within studies using multilevel models with cluster-robust inference, these moderator effects were reduced and no longer statistically robust. Sensitivity analyses confirmed the overall efficacy estimate was robust to study quality concerns and potential publication bias.

EPNs provide reliable biological control of vine weevil larvae under field and semi-field conditions, with effectiveness enhanced by warmer soil temperatures and protected growing environments. Although average effects are large and consistent, practitioners should expect considerable variability in outcomes and prioritise applications during warm conditions in protected environments where feasible. A lack of robust differences among species suggests that selection can be based on practical considerations such as cost and availability. © 2025 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.