Sustainability of strategies for Ostrinia nubilalis management in Northern Italy: Potential impact on beneficial arthropods and aflatoxin contamination in years with different meteorological conditions

The European corn borer (ECB), Ostrinia nubilalis Hübner (Lepidoptera: Crambidae), is a key pest of maize (Zea mays L.). In Northern Italy, larvae of the 2nd generation may damage cobs and kernels and the feeding activity can promote the proliferation of aflatoxigenic fungi, such as Aspergillus flavus, the major producer of aflatoxin B1 (AFB1). During 2017–2018, the efficacy of two strategies to control ECB in maize was assessed. Biological control strategy (Trichogramma brassicae Bezdenko and Bacillus thuringiensis Berliner), conventional chemical strategy (chlorantraniliprole) and an untreated control were compared to assess: i) the effect of the strategies on ECB infestation; ii) the association of ECB and AFB1 kernels contamination; iii) the impact of the strategies on beneficial arthropods. The conventional chemical strategy demonstrated the best control of ECB infestation, followed by biological control strategy and the untreated control. No significant differences in maize yield were found among strategies. The role of ECB on AFB1 concentration was demonstrated only in 2017, when higher level of infestations occurred simultaneously with an extended period of drought and high temperatures, sanctioning the important role of meteorological conditions on AFB1 contamination. The activity density of ground beetles, rove beetles and spiders and the mean number per leaf of the most abundant beneficial insects dwelling on plants (coccinellids, predatory thrips and lacewings) did not show significant changes between pre-and post-treatment with chlorantraniliprole, highlighting the selectivity of this pesticide in the short time. This study provides some contribution for the reduction of non-renewable input in Italian maize fields, demonstrating that biological control strategy, although less effective than conventional chemical control, can be a feasible approach to control ECB second larval generation, without any increment of AFB1 level in grains and yield loss.