Effect of weeds on insect pests of maize and their natural enemies in suthern Mexico / Dora Isabel Penagos Torres

Tesis Maestría en Ciencias en Recursos Naturales y Desarrollo Rural El Colegio de la Frontera Sur 1999

Bibliografía: hojas 19-23

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1. A study performed on the Pacific coastal plain of Chiapas, Mexico focused on the prevalence of maize crop infestation by insect pests, the prevalence of parasitism of pests and the abundance of insect predators in maize plots with weeds compared to plots under a regime of rigorous weed control. Sampling was conducted on four occasions at 20, 32, 44 and 56 days post-planting. Data were subjected to repeated measures analysis. 2. Infestation of maize by fall armyworm larvae, Spodoptera frugiperda (Noctuidae), was overall twice as great in plots with strict weed control compared to weedy plots. The number of other phytophagous Lepidoptera, leafhoppers, phytophagous bugs and thrips was not significantly affected by the presence of weeds. The number of plants infested by aphids, fluctuated at each sample point whereas the prevalence of nitidulid beetles, was consistently lower in the presence of weeds. 3. The density of predatory Coleoptera on maize plants increased significantly in plots with weeds between the first and second sample points. The occurrence of other insect natural enemies (earwigs, lacewings, syrphids, ants etc.) on maize plants increased significantly during the study period but was not significantly affected by the weed control regime. 4. More than double the number of arthropods were captured in pitfall traps placed in weedy compared to weed-controlled plots. The overall capture of carabid beetles was significantly higher in weedy than in clean plots. 5. Overall levels of parasitism by Chelonus insularis (Braconidae) were 27.0% in clean blocks and 29.2% in weedy blocks. S. frugiperda egg masses placed in experimental plots at 23 days post-planting suffered significantly higher incidence of parasitism in clean plots (42.0%) compared to those placed in weedy plots (3.75%). 6. The presence of weeds did not affect maize plant height, the levels of plant damage, or the yield of grain from plants under each type of weed regime. eng

Entomología Tropical