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Research Project: Biological Control and Integrated Management of Invasive Arthropod Pests from Europe, Asia, and Africa

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Title: Evaluation of three European populations of Diadegma semiclausum as potential biological control agents for Plutella xylostella in the USA

Author
item DESURMONT, GAYLORD - European Biological Control Laboratory (EBCL)
item GOLS, RIETA - University Of Wageningen
item BON, MARIE-CLAUDE - European Biological Control Laboratory (EBCL)
item KASHEFI, JAVID - European Biological Control Laboratory (EBCL)
item BLANCHET, ARNAUD - European Biological Control Laboratory (EBCL)
item COELHO, BENJAMIN - Universite De Tours
item GUERMACHE, FATIHA - European Biological Control Laboratory (EBCL)
item KERDELLANT, ELVEN - European Biological Control Laboratory (EBCL)
item MENOUILLARD, MILLA - Université Jean-Monnet
item LARA, RICKY - California Department Of Food And Agriculture

Submitted to: Journal of Pest Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/10/2025
Publication Date: 9/24/2025
Citation: Desurmont, G.A., Gols, R., Bon, M., Kashefi, J., Blanchet, A., Coelho, B., Guermache, F., Kerdellant, E., Menouillard, M., Lara, R. 2025. Evaluation of three European populations of Diadegma semiclausum as potential biological control agents for Plutella xylostella in the USA. Journal of Pest Science. 98:2567-2580. https://doi.org/10.1007/s10340-025-01957-4.
DOI: https://doi.org/10.1007/s10340-025-01957-4

Interpretive Summary: Agricultural insect pests are particularly problematic when they develop resistance to insecticides. Such is the case of diamondback moth (DBM), a devastating pest of cole crops (cabbage, kale, cauliflower...). Biological control (the use of beneficial organisms to control pests) is a sustainable and environmentally-friendly alternative to chemical control that align with global goals for agriculture. Here we evaluated a beneficial insect native to Europe that attack caterpillars, the specialist parasitoid Diadegma semiclausum, for control of DBM in the USA. We compared three European populations, including two that are adapted to warm climates. Results showed that this parasitoid is effective against DBM, both under laboratory and semi-field conditions, and that its presence does not negatively affect a parasitoid that is already present in the USA, Diadegma insulare. However, D. semiclausum was less successful at attacking caterpillars that had already developed insecticide resistance, suggesting that it would be more likely to establish and be effective in pesticide-limited environments such as organic farms than in conventionally-managed fields.

Technical Abstract: The diamondback moth Plutella xylostella is a devastating pest of cruciferous crops known to develop high levels of insecticide resistance. Here, we examined the possibility of classical biological control against this pest in the USA via the introduction of a specialist larval parasitoid, the ichneumonid Diadegma semiclausum. Using three populations of D. semiclausum from France, Greece, and the Netherlands, we compared body mass, longevity, sex ratio, and egg load of the parasitoid populations as well as their performance on their original host population and two novel host populations from the USA (one resistant to insecticides and one susceptible). In addition, the performance of D. semiclausum was evaluated under semi-field conditions with four commercial varieties of cruciferous crops, and a competition experiment was conducted with Diadegma insulare, the main parasitoid of diamondback moth in North America. Results revealed significant differences in mass, sex ratio, and egg load among the parasitoid populations. All parasitoid populations were able to successfully develop in the two USA host populations, but parasitism success was lower on the insecticide-resistant host population. Parasitism success and parasitism rates were higher on the original than on the USA host populations. In semi-field cages, parasitism rate was similar on the four crop varieties and was positively correlated with ambient temperature. Finally, D. semiclausum parasitism rate was 6.7 times higher than that of D. insulare, and parasitism rates of the two parasitoids were additive when they were foraging together. These findings provide a strong basis to select a D. semiclausum population likely to succeed if introduced in the USA and improve control of diamondback moth alongside D. insulare.