Antifeedant effect of non-crucifer extracts on adults of Microtheca ochroloma Stål (Coleoptera: Chrysomelidae)

Microtheca ochroloma causes economic loss to farmers cultivating crucifer vegetables on organic farms. Various cultural, biological, and chemical control methods have been tested against this beetle, but the isolated use of each tactic appears to be insufficient to manage this pest. Trap cropping has shown promising results, but the use of another strategy to make the crop unattractive or unsuitable to the insect is needed to push the insect away from the main crop and concentrate it on the trap crop. Therefore, the objective of this study was to evaluate the effect of 10 non-crucifer plant extracts on leaf consumption by adults of M. ochroloma. Adult beetles were allowed to feed for 48 h on pieces of bok choi leaves sprayed with one of 10 non-crucifer extracts or 0.1% Tween 20 only (control), after which the leaf area consumed was measured. In a second experiment, a commercial product containing azadirachtin was tested. Leaf consumption during 48 h was compared between the treatment and the control (deionized water). Adults consumed 41- 44% less leaf area treated with neem, hyssop and thyme oil compared to leaves treated with oils of garlic, marjoram, lavender, eucalyptus, pepper, sage, and the control. Similarly, adults consumed 45% less leaf area sprayed with azadirachtin compared to leaves treated with water only. The use of a product containing azadirachtin can potentially reduce the impact of this pest on the crop and could be used as part of an IPM program against this pest.