Pest Control with Proteinase Inhibitors: Is It Compatible with IPM Strategies?

In recent years, several studies have demonstrated the potential of proteinase inhibitors (PIs) for the control of various pests and pathogens. Used as a component of an integrated pest management program, such an approach must, however, be carefully considered, given the possible risks of interference with other control methods. For example, we are analyzing the effect of oryzacystatins (OCI and OCII), two cysteine PIs naturally occurring in rice grains, against digestive proteinases of Amblyseius californicus (AC), a native predator of the two-spotted spider mite (SM; Tetranychus urticae). Electrophoretic analyses have shown the existence in SM extracts of a major cysteine proteinase form strongly inhibited by OCI, indicating the potential of this inhibitor for SM control. However, similar analyses revealed a strong affinity between proteinases from AC extracts and OCs. Thus, despite their potential for SM control, plant cystatins may represent growth-suppressing compounds for AC. Work is currently underway to determine the usefulness of OCI-expressing transgenic plants for SM control, and to assess the compatibility of this control with an AC-based biological control strategy.