Traditional fertilization and its effect on corn insect populations in theGuatemalan highlands

Cakchiquel farmers in Patzun, Guatemala stated that pest populations have i ncreased in corn crops since they abandoned organic fertilization and adopt ed synthetic fertilizers. Given the dearth of scientific information about the effects of fertilization practices on pests, a controlled experiment wa s performed to elucidate these interactions. Pests, their natural enemies, and nutritional status were compared among corn plots with synthetic and or ganic fertilizers, and a control without fertilizer. Corn in fields treated with organic fertilizer applied for at least 2 years hosted fewer aphids ( Rhopalosiphum maidis) than corn treated with synthetic fertilizer. This dif ference seems attributable to high concentration and total content of folia r nitrogen in corn in the synthetic fertilizer plots, although numbers of S podoptera frugiperda showed a weak negative correlation with increased nitr ogen levels. Coccinellidae populations were higher in plots with high aphid populations, but only where organic fertilizer was applied. There were no significant yield differences among treatments. (C) 2001 Elsevier Science B .V. All rights reserved.