EFFICACY OF OIL TREATMENTS OF LEGUME SEEDS FOR CONTROL OF ASPERGILLUS AND ZABROTES

Five oils (i.e. an Ecuadorian vegetable oil, which is a mixture of soybean and corn oils; mineral oil; and three soybean oils differing in degree of saturation) were applied at the rate of 5 ml kg-1 of garden pea, Pisum sativum L., seeds to evaluate their effectiveness in decreasing physiological ageing and infection by the storage fungus, Aspergillus ruber (Konig, Spieckermann and Bremer) Thom and Church. Dry beans, Phaseolus vulgaris L., were treated with the same oils to determine the effect of the oils on oviposition and survival of the Mexican bean weevil, Zabrotes subfasciatus (Boheman). The oil treatments had no effect on seed viability, vigour, field emergence, or adsorption of moisture from humid air. Both mineral oil and the highly saturated soybean oil reduced by 50% the levels of seed infection by A. ruber. All oils reduced weevil oviposition and decreased embryo and/or larval survival in comparison with the untreated seeds. The highly saturated soybean oil was most detrimental to both oviposition and insect survival. The oils protected seeds even after storage: < 50% as many insects emerged from eggs oviposited on treated than from untreated seeds when exposed to insects 6 weeks after treatment.