Evaluation of strip-intercropping systems of corn and clover in biocontrol of the European corn worm, Ostrinia nubilalis (Hübner)

The European corn worm, Ostrinia nubilalis (Hübner) is an important pest of corn in Iran. In this research, the influence of corn monoculture and also, three strip-intercropping systems including three, six and nin rows of corn with three rows of clover were evaluated on the natural enemies diversity of O. nubilalis, the proportion of predators/prey density and finally, the percentage of parasitized eggs and larvae in experimental fields in Ardabil region in 2014 and 2015. In this study, eight predator species, five larval parasitoid species and one egg parasitoid species were collected and identified which amongst them, Orius niger (Wolff), Lydella thompsoni Herting, Bracon hebetor Say and Trichogramma brassicae Bezdenko had the high relative abundance in the tested cropping systems. The Shannon diversity index (H) in each of the three intercrops was significantly greater than in corn monoculture. The values of Morisita–Horn index (CMH) between corn monoculture and each of the three intercrops (CMH ≤ 0.893) were lower in comparision with the values of this index among the three intercrops (CMH ≥ 0.977). In two years, the proportion of predators/prey, and the percentage of parasitized eggs and larvae of O. nubilalis in each of the three intercrops were significantly higher than in corn monoculture. Implementation of these cultivation systems in the corn fields is an important step in the management of O. nubilalis.