Traditional fertilization and its effect on corn insect populations in the Guatemalan highlands

Cakchiquel farmers in Patzún, Guatemala stated that pest populations have increased in corn crops since they abandoned organic fertilization and adopted synthetic fertilizers. Given the dearth of scientific information about the effects of fertilization practices on pests, a controlled experiment was performed to elucidate these interactions. Pests, their natural enemies, and nutritional status were compared among corn plots with synthetic and organic 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 difference seems attributable to high concentration and total content of foliar nitrogen in corn in the synthetic fertilizer plots, although numbers of Spodoptera frugiperda showed a weak negative correlation with increased nitrogen 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. © 2001 Elsevier Science B.V. All rights reserved.