Hymenopteran, parasitoid wasps have good potential for use in integrated pest management (IPM); for example, the
gregarious ectoparasitoid, Eulophus pennicornis, has been suggested as a biological control agent for larvae of the tomato
moth (Lacanobia oleracea L.). However, the processes by which such parasitic larvae are able to utilize the nutritional
resource provided by the host have been little studied. Protease activity was present in E. pennicornis larvae, and characterization
of the enzymes responsible for proteolysis was performed using a range of synthetic substrates and specific inhibitors.
Serine protease enzymes was both trypsin- and chymotrypsin-like activities were present. A range of plant-derived serine
protease inhibitors was tested for activity against these enzymes. Certain inhibitors, notably soybean Kunitz inhibitor
(SKTI), inhibited enyzme activity by >80% at <10−5M. When SKTI was fed to L. oleracea larvae in an artificial diet,
the inhibitor was subsequently detected within the larval haemolymph, showing that protease inhibitors in the host diet
can be delivered to a parasitoid via the host haemolymph. If transgenic plants expressing foreign protease inhibitors for
protection against insect pests are to form a component of IPM systems, possible adverse effects, whether direct or indirect,
of transgene expression on parasitoids like E. pennicornis should be considered.