© 2007 The Authors Entomologia Experimentalis et Applicata 126: 28–39, 2008 28 Journal compilation © 2007 The Netherlands Entomological Society DOI: 10.1111/j.1570-7458.2007.00630.x Blackwell Publishing Ltd Reduction of damage by the Mediterranean corn borer, Sesamia nonagrioides, and the European corn borer, Ostrinia nubilalis, in maize fields by a trifluoromethyl ketone pheromone analog J. Solé 1 , A. Sans 1 , M. Riba 1 , E. Rosa 2 , M.P. Bosch 2 , M. Barrot 3 , J. Palència 3 , J. Castellà 3 & A. Guerrero 2 * 1 Centre UdL–IRTA, Universitat de Lleida, Rovira Roure 191, 25198 Lleida, Spain, 2 Department of Biological Organic Chemistry, IIQAB (CSIC), Jordi Girona Salgado 18-26, 08034 Barcelona, Spain, and 3 Sociedad Española de Desarrollos Químicos, S.A. (SEDQ), Avda Diagonal, 352, 08013 Barcelona, Spain Accepted: 3 September 2007 Key words: pheromone antagonists, pest management, Lepidoptera, Noctuidae, Crambidae, Zea mays, Poaceae, mating disruption Abstract Large-scale field experiments on the Mediterranean corn borer, Sesamia nonagrioides Lefèbvre (Lepidoptera: Noctuidae), were carried out in 2004–2006 on maize [Zea mays L. (Poaceae)] fields using (Z)-11-hexadecenyl trifluoromethyl ketone, an antagonist analog of the pheromone of this species, to evaluate a possible reduction of damage caused by this pest. The effect of the treatments on the European corn borer, Ostrinia nubilalis Hübner (Lepidoptera: Crambidae), a sympatric species, was also determined. Evaluation of the success of the experiments was assessed by counting (i) the number of males caught by pheromone traps in treated and untreated fields, (ii) the number of plants attacked by both insects in both plots, and (iii) the number of larvae present in infested plants in both fields. Effectiveness of the treatment was high for the second generation of the Mediterranean corn borer, the most harmful to the crop (86 – 90% reduction in the number of plants attacked and 67 – 98% reduction in the number of larvae per plant in treated fields in comparison to untreated fields), and moderate for the third generation (reduction of 41–71% and 33–77%, respectively). Treatments were also effective for the second generation of the European corn borer (61–75% reduction in the number of plants attacked, 58 – 78% reduction in the number of larvae found per plant) as well as for the third generation (69 – 97% and 70 – 98% reduction, respectively). By plotting the amount of the antagonist remaining on the dispensers after 40 – 45 days of exposure with time, the mean release rate of the compound was calculated to be 2.2%/day in 2004, 1.95%/day in 2005, and 2.1%/day in 2006, with 26% of the initial compound remaining after 20 days of experimentation. The emission rate appears to cover the flight of the most damaging second generation of both insects. Prospects of using trifluoromethyl ketones as new potential agents for pest control are also outlined. Introduction The Mediterranean corn borer (also known as corn stalk borer), Sesamia nonagrioides Lefèbvre (Lepidoptera: Noctuidae), is an important pest of maize [Zea mays L. (Poaceae)] in the Mediterranean region (below 45°N parallel) and North Africa (Anonymous, 1979). A number of broad spectrum insecticides have been used to control the pest but with little success owing to the endophytic habits of the species, high costs, and negative effects on secondary pests, such as aphids, mites, and leafhoppers. The sex pheromone of the moth was identified in 1985 as a mixture of ( Z )-11-hexadecenyl acetate ( Z 11 - 16:Ac) and ( Z )-11-hexadecenol ( Z 11 - 16:OH) (Sreng et al., 1985). Later, Mazomenos (1989) found that the four-component blend of Z 11 - 16:Ac, Z 11 - 16:OH, ( Z )-11-hexadecenal ( Z 11 - 16:Ald), and dodecyl acetate (12:Ac) in a 69:8:8:15 ratio considerably improved the efficiency of the pheromone. * Correspondence: A. Guerrero, Department of Biological Organic Chemistry, IIQAB (CSIC), Jordi Girona Salgado 18-26, 08034 Barcelona, Spain. E-mail: agpqob@iiqab.csic.es