Antibiosis of the Aqueous Extract of Neem against Agave Weevil Adults

Antibiosis of the aqueous extract of neem against agave weevil adults
Jaime Molina-Ochoa¹, Fernando Jovany Castillo-Ceja¹, Martín González-Ramírez¹, Juan Manuel González-González¹, Roberto Lezama Gutiérrez¹, Salvador Guzmán-González¹, and John E. Foster^2
1Universidad de Colima, Facultad de Ciencias Biológicas y Agropecuarias, Tecomán Colima 28930, México, e-mails: jmolina@ucol.mx, glezglez@ucol.mx,
²University of Nebraska Lincoln, Department of Entomology, 202 Entomology Hall Lincoln, NE 68583-0816, USA

 The agave weevil, Scyphophorus acupunctatus Gyllenhal, is a destructive pest, it is a curculionid with a broad distribution in Mexico and causes significant economic losses in the agave plantation as well as to the tequila industry. Usually this insect pest is controlled with synthetic insecticides; however, the public ecological and environmental concerns demanded new alternatives to reduce the pest populations. The products obtained from the neem plant (Azadirachta indica A. Juss (Neem) have been studied to control insect pests and diseases. The aqueous extracts of the neem seed contain several secondary metabolites such as terpenoids, phenols, and aminoacids. They show several host plant resistance mechanisms against insect pests. In this study we determined the antibiotic activity against agave weevil adults under laboratory conditions. We used five increasing concentrations: 0, 5, 10, 15, and 20% of a 99.6% concentrated aqueous extract. Adults of the agave weevil were placed individually in crystal flasks of 100 ml containing 2 x 2 cm²  of papaya stalk, Carica papaya L., previously soaked in each concentration during 30 seconds, then a metal lid was placed on. The check and treated papaya portions were replaced each 2 days. Treatments were arranged in a bifactorial complete randomized design with 25 treatments (Factor A=concentrations; Factor B= exposure time) with 4 replications and 5 experimental units per replications were used. The evaluated variables were: body weight at 0, 2, 4, 6, and 8 days post-treatment, and percent mortality. Antibiotic effects were determined in the agave weevil adults, the concentrations of 15% and 20% caused cumulative mortalities higher than 27%, and they caused body weight reductions due to a food dissuasive response.

 Key words: Scyphophorus acupunctatus, agave weevil, antibiosis, mortality, food dissuasive.