Quantifying the effects of previous crop, tillage, cultivar and triazole fungicides on the deoxynivalenol content of wheat grain - a review

Deoxynivalenol (DON) is a mycotoxin produced by fungi of the genus Fusarium. Maximum tolerable DON concentrations for grain and selected wheat products were laid down by national and European legislative institutions to protect consumers from health risks associated with the intake of this mycotoxin. Among the factors that can be controlled by growers, previous crop, tillage, wheat cultivar and fungicide regimes were identified as the most important variables for DON contamination of wheat. Beyond the identification of the risk factors, their quantitative impact needs to be known for integrated control strategies. The purpose of this review was to extract information on the magnitude of DON reductions caused by agronomic methods or fungicide applications from recent publications. Efficacies of fungicides containing triazoles as active ingredient differed significantly (P = 0.004) in the studies published recently. This effect was solely based on a poor performance of fenbuconazole. No significant differences between triazole fungicide efficacies were observed after excluding fenbuconazole from the analysis. On average, triazole fungicides applied around the time of wheat anthesis reduced the DON content to 53 +/- 4% of the grain obtained from untreated control plots. Planting wheat after crops other than maize reduced the DON content to 33 +/- 11% compared to maize as the pre-crop. Using a mouldboard plough lowered the DON content to 33 +/- 7% compared to minimal or no tillage plots. Cultivating commercially available moderately susceptible cultivars decreased the DON content down to 24 7% compared to susceptible cultivars. Hence, careful choice of cultivar is currently the most effective agronomic method to decrease DON contamination levels in wheat followed by ploughing, avoiding maize as pre-crop and applying triazole fungicides at wheat anthesis. If DON contents of reference scenarios (for instance long term average DON contamination levels for particular cultural practices and regions) are known, the factors extracted in this review may be useful to estimate how many risk factors need to be avoided to decrease DON contents below the limits given in the actual legal regulations.