DRIED LEAVES FROM ROCKY-MOUNTAIN PLANTS DECREASE INFESTATION BY STORED-PRODUCT BEETLES

Leaves of two highly aromatic plants, Arte,misia tridentata (Nutt.) and Monarda fistulosa L., prepared according to a patented process, inhibited oviposition by the Mexican bean weevil, Zabrotes subfasciatus (Boheman), in beans at concentrations less than 1% w/w. Both plant species were less effective against the rice weevil, Sitophilus oryzae L., in wheat, with only M. fistulosa exhibiting any concentration-dependent activity. The maximal control achieved against this species was less than 50% at 3% w/w. Two less aromatic plant species, Balsamorhiza sagittata (Pursh.) Nutt, and Geranium viscosissimum Fisch. and Mey., caused only low levels of inhibition against both insect species. Volatiles probably caused the response to A. tridentata and M. fistulosa, while the asymptotic concentration dependence for the less volatile plant material was likely caused by behavioral factors related to the physical presence of foreign particulate matter in the foodstuff. Chemical analysis indicated that most of the volatile components from the dried leaf material from all species were terpenoids, with camphor (9.7 mg/g) and 1,8-cineole (4.0 mg/g) being most abundant in A. tridentata and carvacrol (26.3 mg/g) being most abundant in M. fistulosa.