| This dissertation is composed of three distinct studies relating to the development of corn pest control techniques in Ecuador. Its emphasizes the diversity of pest problems and control options of small farmers, in relation to the constraints under which they live and cultivate their crops.; Study I analyzes a traditional non-chemical pest control technique, developed by small-farmers, in which castor leaves are placed in recently planted corn fields to reduce beetle pest populations. Pseudothinobatis rufinasus, Fam. Tenebrionidae, prefers castor leaves over corn, cabbage or plain paper, yet they do not consume the leaves. Beetles associated with castor leaves for 12 hours or more exhibit paralysis but the leaves are not directly toxic to the beetles. In the field, the paralysis prevents beetles from hiding in the soil and direct exposure to the sun significantly increased their mortality. Castor leaf applications illustrate a use of natural chemicals to manipulate a pest population by disrupting its innate behavior.; Study II compares insect infestations and damage in a traditional corn variety and a new early maturing variety, cultivated with and without chemical fertilizer. There were no significant yield differences between the traditional variety and the new variety. Lepidoptera larva (Agrotis deprivata and Dargida grammivora) were the principal foliar pests. Foliar damage was minimal and similar for the two varieties. Insect infestations in ripening ears were significantly higher in the new variety. The percent of ears damaged by Lepidoptera larva (Heliothis zea and A. deprivata) for the traditional and the new varieties was 24.4% and 35.6%, respectively, and 19.5% and 24.4% for Euxesta eluta (Order Diptera). Ear damage was not affected by chemical fertilizers. The new variety's greater susceptibility to ear damage may reduce its adoption by the small-scale farmers for whom it was developed.; Study III, conducted in coastal Ecuador, establishes economic thresholds for fall armyworm (Spodoptera frugiperda). Yield reductions and the impact of fall armyworm control declined as the plants matured. Thresholds increased from approximately 9 to 40% infestation levels one to six weeks after plant emergence. Pesticide applications also reduced Diatraea saccharalis. Future studies should separate the effects of different pests over time and determine the effects of control on each. |
