Effect of sowing date and insecticide application against European corn borer (Lepidoptera: Crambidae) on fumonisin contamination in maize kernels

Fusarium verticillioides, a known producer of fumonisins, has been reported to be the most common pathogen of maize causing Fusarium ear rot and grain fumonisin contamination. Field tests were carried out in 2004 and 2005 growing seasons in two sites located in the North of Italy to determine the effects of sowing date and insecticide treatment against European corn borer (ECB, Ostrinia nubilalis Hübner) on maize susceptibility to Fusarium ear rot and fumonisin contamination under natural infection conditions. Two sowing dates (at about 25-30 day intervals) and two insecticide application treatments with lambda-cyhalothrin (at 7 and 14 days after the ECB flight peak) were compared with the untreated control in each year/site. Ears were rated for both incidence and severity of ECB damage and Fusarium ear rot at harvest. Harvested kernels were analyzed for fumonisin B1 (FB1) and B2 (FB2) contents. Insecticide treatments significantly reduced the ECB infestation compared to the untreated control. The insecticide treatments applied 7 days after the ECB flight peak controlled insect damage significantly better than those applied later. The ECB damage severity was also higher for the later than the earlier sowing date (14%) compared to the earlier one. A significant effect of sowing date and insecticide application on Fusarium ear rot was evidenced. For the earlier sowing date treatments, ear rot incidence and severity reductions of 13% and 16%, respectively, compared to those of later sowing dates were noted. Insecticide applications to plants resulted in lower ear rot severity than the untreated control (up to 29%). Maize sowed earlier and treated with insecticide 7 days after the ECB flight peak resulted in a significantly lower grain fumonisin concentration (up to 67%), compared to those of untreated and late sowed maize. In Mediterranean areas, the choice of an early sowing date and appropriate treatments with pyrethroid insecticides against ECB might represent a useful tool to limit raw maize fumonisin concentration to levels below the EU maximum admissible level recently fixed by the Commission.