Abstract
In field experiment carried out in the 2018 growing season we tried to show the inverse relation between the efficacy of fusarium head blight (FHB) chemical control and the deoxynivalenol (DON) concentration in harvested kernels. The wheat cultivar Tbio Mestre was established under no-till in soybean residues and in winter rotation with black oats. The leaf rust and yellow spot control was performed during the vegetative stage by spraying the whole experimental area with three applications of epoxiconazole + krezoxim methyl (0.7 L/ha). The most potent fungicides metconazole + pyraclostrobin (1.0 L/ha) + mancozeb (2.0 kg/ha), prothioconazole + trifloxystrobin (0.4 L/ha) and pydiflumetofen (1.0 L/ha) were compared to control FHB. Disease incidence in spikes, incidence in spikelets, or spikes severity, grain weight and yield were evaluated. DON concentration was. Using the most efficient technology available for FHB control, the hypothesis of the inverse relationship between disease intensity occurring naturally in spikes, and deoxinivalenol (DON) concentration in the harvested grains was confirmed. DON concentration in unsprayed grains was 3,675 and in the best treatments 821 to 1,067 ppb.
Highlights
In the 2018 year the wheat (Triticum aestivum L.) Brazilian consumption was 11 million tons and the national production only 4,3 million tons
Field was managed in terms of fertilizer application, and pest management according to Zadoks et al (1974) throughout the experimental area, including the control plots, and independently of fusarium head blight (FHB) control
Control of leaf diseases was independent of FHB and performed in the whole experimental area including the control plots
Summary
In the 2018 year the wheat (Triticum aestivum L.) Brazilian consumption was 11 million tons and the national production only 4,3 million tons. The difference between demand and production shows the great challenge of making the country self-sufficient (CONAB, 2018). Producing wheat where environmental adversities are constant, as in South of Brazil, is not an easy task. The constraints are directly related to the excess of rains after flowering to cereal ripening. Wheat crop requires approximately 312-550 mm rain distributed throughout its cycle. South of the 24oS parallel, the normal from June to November is 944 mm, much higher than the crop requirements (Westphalen, 1982)
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