Abiotic benefits of intercropping legumes and maize to reduce pests

This study was aimed to evaluate the effect of intercropping maize (Zea mays L.) with different types of bean (Phaseolus spp.) on bean pests, diseases and yield. The experiment was design as randomised complete block design (RCBD) with three replicates at Sari Agricultural Sciences and Natural Resources University in the north of Iran during 2010. The experimental treatments were mono-cropping of maize, white bean, bush bean, red bean, pinto bean, sword bean and intercropping of maize with bean types a 50:50 ratio. Pests and diseases infection was recorded under naturally infected in the field. The results showed that the two-spotted spider, Tetranychus urticae, population density was decreased markedly (62% and 83%, respectively) in sword bean and white bean intercropped with maize as compared to solitary treatment. The leaf miner, Delia platura, severity on bean was reduced up to 30% compared to mono-cropping treatment. In contrast, the population of thrips (Thrips tabaci) in intercropping treatments was increased up to 30% as compared to mono-cropping. Furthermore, the rust disease rate caused by Uromyces appendiculatus was reduced significantly in pinto bean or sword bean with maize (37% and 98%, respectively) compared to pinto bean and sword bean sole cropped. Shannon-Wiener and Simpson index indicates that the diversity of pests is more in intercropping than the mono-cropping by 4.5% and 1.6%, respectively. However, the degree of red bean and pinto bean pest suppression by intercropping increased as the pest community in the surrounding mono-cropping increased. It is recommended that further studies focussed on the possible time for mix sowing to controlling pest and disease.