No abstract

Fungicides and, for the first time, microalgal phenolic extracts (MPE) from Spirulina sp. and Nannochloropsis sp. were applied on maize culture media under field conditions to evaluate their ability to minimize Fusarium species development and fumonisin production. An in vitro assay against F. verticillioides was carried out using maize grains as the culture medium. An open-field experiment was carried out in Northwest Italy under natural infection conditions. The compared treatments were factorial combinations of two insecticide treatments (an untreated control and pyrethroid, used against European Corn Borer), four antifungal treatments (an untreated control, MPE from Spirulina sp., MPE from Nannochloropsis sp., and a synthetic fungicide), and two timings of the application of the antifungal compounds (at maize flowering and at the milk stage). The MPE compounds were capable of inhibiting fumonisin production in vitro more efficiently than tebuconazole. Insecticide application reduced the infection by Fusarium species and subsequent fumonisin contamination. However, fumonisins in maize fields were not significantly controlled by either fungicide or MPE application.

No abstract

The research investigated ways to enhance maize yield in intensive maize cropping system by evaluating the effect of high planting densities combined with foliar fungicide treatments. The considered assessments were fungal leaf disease, biomass and grain yield and methane production through anaerobic fermentation. The experiment was conducted in the years 2012 and 2013. The treatments compared at each location were factorial combinations of two plant densities and three fungicide applications. A standard planting density (StD, 7.5 plants m–2 on a 0.75 m interrow spacing) was compared with the high density (HiD, 10 plants m–2 on narrow 0.5 m inter-row spacing). Two fungicides, pyraclostrobin at 0.2 kg AI ha–1 and a mixture of pyraclostrobin and epoxiconazole at 0.2 and 0.075 kg AI ha–1 respectively, were applied at the tassel emergence stage and compared with an untreated treatment. The HiD system positively increased the silage maize yield (+16%), grain (+17%) and methane yield per hectare (+19%) in comparison to the StD. The fungicide application significantly restrained foliar disease symptoms only in 2012. Fungicide did not affect plant silage composition (protein, starch or fibre content) and methane yield, conversely it significantly increased grain yield for both planting density systems (+5%). The overall boost in yield obtained by combining both strategies in an intensive system, HiD combined with the fungicide, was +24% for methane and +21% for grain yield compared to StD without fungicide application. This work proved that an intensive high planting system with up to 10 plants m–2, supported by leaf fungicide treatments, can lead to a real yield enhancement of both maize grain and silage.

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.