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  • Author or Editor: M. Blandino x
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Ostrinia nubilalis (Hübner) (European corn borer) is the main maize pest in Central and South Europe and it promotes Fusarium verticillioides infection on maize grains, which is able to produce fumonisins. The objective of this study was to determine the effect of the timing of pyrethroid treatments on European corn borer damage, fungal ear rot and fumonisin contamination. The field experiments were performed from 2005 to 2007 in NW Italy. Four application timings were compared to an untreated control. The insecticide treatments were applied at approximately 10 days intervals, starting from the end of flowering. The last treatment was performed approximately 15 days after the ECB flight peak. At harvest, the ears were rated for the incidence and severity of European corn borer damage and fungal ear rot symptoms, and the harvested kernels were analyzed for fumonisins B 1 +B 2 . In all the years, the treatments applied 7–10 days before the European corn borer adult flight peak showed the best efficacy to control insect damage on ears. Fungal ear rot and fumonisin contamination were clearly affected by European corn borer control. The occurrence of this mycotoxin in plots treated at the best pyrethroid application timing was significantly reduced, on average by 76%, compared to the untreated control. Furthermore, early insecticide applications, at the end of maize flowering, showed significantly lower fumonisin contamination than treatments applied at approximately 15 days after the adult flight peak. This research indicates that the production of maize kernels with low fumonisin content may be enhanced by a correct timing of the insecticide application against second generation European corn borer.

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Fusarium head blight (FHB) of small grain cereals is a worldwide disease that reduces yield and causes deoxynivalenol (DON) contamination in grains. Non-decomposed residues from the previous crop present on the soil surface are considered the principal inoculum sources for Fusarium graminearum and F. culmorum, the most important Fusarium species that cause FHB in Europe. The objective of this study was to investigate the effect of the amount of previous residues on the FHB disease under natural conditions and on DON contamination in soft wheat following grain maize. Field experiments were conducted in two cropping seasons and two sites to compare four maize residue densities on the soil surface and in the first 10 cm of soil in tilled and non-tilled fields. Ploughing to a 30 cmdepth significantly reduced FHB severity (by 63%) and DON occurrence (by 80%) in each year and site. FHB severity and DON contamination significantly increased with the density of the residues left by the preceding crop. This study confirms that conservation tillage may increase DON concentration in wheat grain compared to ploughing which buries residues. This increase varies to a great extent not only because of the annual weather conditions and the nature of the preceding crop, but also because of the amount of infected crop residues remaining on the soil surface, which depends on the soil tillage methods and the preceding crop.

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Foliar fungicides are widely used to control pests on several crops and, from mid-2000s, have become more common on maize. The yield advantages derived from foliar fungicides on maize, as for other crops, could be related not only to the direct control of the disease, but also to physiological effects on the plant. The aim of the research was to evaluate the response of maize to the application of an azoxystrobin and propiconazole mixture. The fungicide was applied to hybrids with different susceptibility to northern corn leaf blight (NCLB) foliar disease at the beginning of stem elongation or at the tassel emergence stage. The best application timing resulted to be at the tassel emergence stage for both pathogen control and grain yield. The treatment effectively controlled disease development on the two hybrids susceptible to NCLB. However, the yield of the moderately-resistant hybrid increased unexpectedly to a comparable extent, even though no significant fungal containment was detected from a visual inspection. The peroxidase and superoxide dismutase activity, the protein leaf content and the translocation efficiency of carbohydrates from the leaf to the ear were not influenced by the fungicide treatments, differently from what had been previously shown on wheat. The authors suggest that rather than the improved metabolism of the reactive oxygen species, the positive effect of the fungicide on the moderately-resistant hybrid is due to other physiological mechanisms. It is hypothesized that the fungicide leads to better yields as it prevents the allocation of metabolic resources to actively defend against the pathogen.

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