Insecticidal activity of some aromatic plants from Croatia against lesser grain borer (Rhyzopertha dominica F.) on stored wheat

摘要

Essential oils and plant dust of four Croatian aromatic plants (Lavandula officinalis Ch., Laurus nobilis L., Rosmarinus officinalis L., Thymus vulgarls L.), were tested for insecticidal activity against lesser grain borer Rhyzopertha dominica F. onmarket and seed wheat under laboratory and storage conditions. An insecticidal effect up to 100 percent mortality of adults was observed over the exposure period. The efficacy of the plant material was compared to a control with no treatment. Doses of essential oils and plant dust were recalculated on 5-kg wheat samples, as follows: 3.75 mL/sample of oils, and 37.5 g/sample of dust. In general, all essential oils exhibited strong insecticidal effect (100 percent mortality of adults after 24 h), with L.nobilis proving most effective in dust form (100 percent mortality of adults after 7-10 days of exposure) under storage conditions. In the control samples, no mortality of adults was recorded. Over the five-month period, damage on wheat was found to be30 percent, while insect population increased up to 190 percent. No changes in quality, colour or flavour of the commercial wheat flour were recorded during the treatment; however, each sample retained the scent of the plants tested. On seed wheat, no negative effect on germination or energy of germination was recorded. These aromatic plant products proved to be partial substitutes for synthetic insecticides if applied to smaller stocks of stored wheat in order to reduce contamination of food and the environment.