Predation by soil inhabiting arthropods in intercropped and monoculture agroecosystems

Experiments were carried out to determine effects of intercropping on macroarthropod predator activity, both diurnal and seasonal, and on relative consumption of lepidopteran pest larvae during a two-year study. Maize (corn, Zea mays) was intercropped into a grass-legume mixture and compared to monoculture maize. There was significantly more predator activity (number of attacks by predators on pest larvae) and predation (number of larvae consumed) in the intercropped system compared with the monocultured treatment during both years of the study. Predator activity and consumption of larvae were greatest at night in both systems and least during the day. However, the intercropped system had significantly more predator activity during each observation over a 24-h period than did the monocultured system. Predator activity and predation did not fluctuate appreciably over the early part of the growing season until August when there was a significant increase in both parameters. Carabid beetle larvae and spiders were the major predators in June, however, in July and August large carabid adults (> 15 mm) became the dominant predators. Significant correlations were found among carabid beetle activity, density estimates of macroarthropods and the number of lepidopteran larvae consumed in these corn agroecosystems. These correlations between techniques and endemic predatory arthropods indicate that predation is a significant factor in reducing pest populations in intercropped agroecosystems.