INSECTICIDAL ACTIVITY OF FLORAL, FOLIAR, AND ROOT EXTRACTS OF TAGETESMINUTA (ASTERALES, ASTERACEAE) AGAINST ADULT MEXICAN BEAN WEEVILS (COLEOPTERA, BRUCHIDAE)

Experiments were conducted to determine speed of action and toxicities of extracts of Tagetes minuta L., a source of naturally occurring ins ecticidal compounds. LC(50) values for male and female Mexican bean we evils, Zabrotes subfasciatus (Boheman), were determined for floral, fo liar, and root extracts of T. minuta. The 24-h LC(50) values ranged fr om 138 mu g/cm(2) for males exposed to the root extract (most suscepti ble) to 803 mu g/cm(2) for females exposed to the foliar extract (leas t susceptible). Increasing the duration of exposure to 48 h decreased all LC(50) values 20-30 mu g/cm(2). Males were more susceptible than f emales. The time to incapacitation for 50% of the test insects (IT50) for floral and foliar extracts indicated fast-acting, volatile compone nts, whereas the root extract data indicated slower-acting components, likely a result of the interaction of photophase with time-dependent efficacy. Floral and foliar extracts of T. minuta may be useful as ins ecticides for controlling stored-product pests.