Management of the Mexican bean weevil by adding aromatic plant derivatives in two dry formulations

Abstract

Background. Zabrotes subfasciatus (Boh., 1833) (Coleoptera: Chrysomelidae: Bruchinae), is considered one of the most important pest of stored beans. Objective. This study reports the possible toxicity and repellence of powders prepared from eight plant species against the Mexican bean weevil in two formulations (dry powder and sachets). Methodology. A 10 * 2 factorial design (10 species * 2 formulations) with 8 repetitions in a completely randomized design was employed. Pots with no powder were used as a negative control, and a pyrethroid insecticide [K-Obiol® 2 DP (deltamethrin, 0.5 g a.i. ton-1)] was applied as a positive control. Results. A mixture of powdered Chenopodium ambrosioides L., Ruta graveolens L. and Mentha pulegium L. added to bean grains was confirmed to be toxic to Z. subfasciatus adults with promising grain protector properties. C. ambrosioides powder had the same effect when in a sachet. A mixture of powdered R. graveolens, M. pulegium and C. ambrosioides with the beans inhibited weevil oviposition. The same effect was achieved for M. pulegium and C. ambrosioides in sachets. A mixture of powdered C. ambrosioides, M. pulegium, R. officinalis and R. graveolens repelled Z. subfasciatus adults from bean grains. Implications. This is the first report of using botanical derivatives by means of sachets or dry formulations, a pre-commercial purpose for aromatic plants with insecticidal/repellent activities. Conclusions. Sachets containing powdered C. ambrosioides and M. pulegium efficiently controlled the Mexican bean weevil in stored beans and constitute an useful tools for domestic grain stock or post-harvest management of organic grains.