Towards an attract-and-reward strategy: evaluating nectar resources and HIPVs under laboratory conditions to enhance Aphelinus mali parasitism activity, a key parasitoid of Eriosoma lanigerum.

BACKGROUND: The attract-and-reward strategy involves attracting natural enemies using volatile compounds or insectary plants and rewarding them with refuge and food sources. Plants with accessible nectar and early bloom together with herbivore-induced plant volatiles, such as phenylacetaldehyde (Pal) and methyl salicylate (MeSA), could enhance populations of Aphelinus mali Haldeman (Hymenoptera: Aphelinidae), a main parasitoid of Eriosoma lanigerum (Hausmann) (Hemiptera: Aphididae).

RESULTS: The extrafloral nectary plant species Euphorbia segetalis was attractive to A. mali, whereas the floral-nectary plants Calendula officinalis, Eruca vesicaria, and Moricandia arvensis, as well as the extrafloral nectary plant Vicia faba, Pal, and MeSA showed no attraction. The most promising nectar resources were V. faba and Vicia sativa. In the first survival experiment, V. faba significantly increased the survival of A. mali (10.5 ± 1.4 days) compared with unfed females (4.4 ± 0.8 days), whereas in the second survival experiment, both V. faba (9.3 ± 1.6 days) and V. sativa (6.1 ± 0.8 days) significantly improved survival compared with unfed females (2.5 ± 0.7 days). However, no differences in egg load were observed when A. mali females fed on different nectar resources.

CONCLUSION: These findings suggest that Euphorbia segetalis is a promising attractant plant for A. mali. Meanwhile, V. faba and V. sativa are promising nectar resources to sustain the parasitoid in early spring when the population of Eriosoma lanigerum is low, and honeydew is scarce. These first results should be complemented with field assays for a better understanding of the effects of these plant species on A. mali. © 2026 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.