Grain Yield Enhancement through Fungicide Application on Maize Hybrids with Different Susceptibility to Northern Corn Leaf Blight

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.