A review of insect prevalence in maize (Zea mays L.) and bean (Phaseolus vulgaris L.) polycultural systems

Tropical agroecosystems often include two or more crops arranged in diverse polycultural patterns. Experimental evaluation of the pest situation in polycultural systems was carried out in several field experiments at CIAT (Centro Internacional de Agricultura Tropical, Palmira, Colombia) with maize and beans in monoculture and polyculture. Beans grown as maize/bean polycultures had 26 percent fewer Empoasca kraemeri Ross and Moore adults than monoculture beans. Similarly the populations of Diabrotica balteata Le Comte were 45 percent less in polycultures. Spodoptera frugiperda (Smith) incidence as cutworm in maize was reduced 14 percent in polycultures. Also these systems had 23 percent less infestation of fall armyworm as whorl feeder. Date of planting affects pest interactions in these systems. For example, maize planted 30 and 20 days earlier than beans reduced leafhoppers on beans by 66 percent as compared to simultaneous planting. Fall armyworm damage on maize was reduced 88 percent when beans were planted 20 to 40 days earlier than the maize. Diversification of monocultural systems with other crops, especially non-host plants, seems to be one effective strategy in tropical pest management. Further research will provide a basis for incorporating practical pest control schemes into the most important intercropping systems in the tropics eng