Influence of Distance from wetland borders on prevalence of insect pests and natural enemies in Maize-Soybean cropping system in Eastern Uganda

Abstract

There has been widespread alteration and simplification of ecosystems, which has affected biodiversity and natural biological pest regulation. Some studies have shown that naturalix biological pest suppression can be achieved in agro-ecosystems when non-crop habitats are large and proximate enough to the crops fields. Although the effect of wetland borders on beneficial arthropods has been studied at small distances, it is not clear how far wetland borders can influence insect pests and natural enemies‘ populations and to what extent the pest-natural enemies‘ interaction in a complex cropping system such as in maize-soybean intercrop can extend from the wetland borders. Therefore, the study was done with the following objectives:- i) To determine the relationship between abundance of insect pests in Maize-Soybeans cropping system and field distance from the wetland border, ii) To determine the prevalence of natural enemies of insect pests of maize-soybeans in wetland vegetation and agricultural fields bordering Naigombwa wetland. Twelve farmers‘ fields planted with maize and soybean intercrops were sampled at varying distances from the wetland borders and sampling of insect pests and natural enemies was done by use of; water traps, pitfall traps, sweep nets and direct observation at two weeks interval from seedling to post flowering growth stages of the crops. It was observed that crop fields further from wetland borders (above 500 meters from wetland borders) had higher pest prevalence, on average 74% for fall armyworm and 7% for maize stalk borer, similarly soybean pests were much abundant in fields further from the wetland borders, meanwhile crop fields closer (within 300 meters from wetland borders registered lower pest prevalence. For natural enemies, closer fields to the wetland borders (82-332 meters) registered high natural enemies populations than further crop fields (568-1068 meters). The results from this study indicated that with ever shrinking natural and semi-natural habitats, management of remaining fragments as well as maintaining semi-natural patches in agro-ecosystems is crucial for sustainable ecological biological pest management.