FUSARIUM HEAD BLIGHT AND DON CONTAMINATION MANAGEMENT IN SOFT AND DURUM WHEAT CULTIVATION - Soybean and Wheat Crops: Growth, Fertilization, and Yield - page 138

contamination in wheat grains are mainly affected by tillage, crop rotation, varieties and
fungicide application (Pirgozliev et al., 2003). None of these strategies on their own are able
to significantly reduce the impact of this disease (Edwards, 2004a).
Although information is available on the basic effect of single agricultural practices on
Fusarium infection and DON contamination in wheat, only a few studies have been made to
quantify the relative importance of each of these factors compared to the others that are
involved and to verify their interactions and combined effects.
Preliminary information on the relative effect of management options on FHB incidence
and DON contamination could be obtained through a simplified approach to calculate the
severity of the effect of the single factors, as proposed by Koch et al. (2006). In this study, the
severity of the effect of the single agricultural practices was calculated as follows: the mean
DON value of the treatment with the highest DON concentration is divided by the mean value
of the lowest treatment.
The data obtained in the experiments conducted by Koch et al. (2006) are reported and
compared in table 5 with other information obtained from the literature and with information
from similar trials conducted in 2005-2007 in 4 sites in northern and central Italy. In all these
studies, the effect of at least two agricultural practices on DON contamination were
compared, in natural inoculated conditions.
Based on these data, the following ranking order can be obtained: susceptibility of wheat
cultivar (1.6-5.6) = the preceding crop (2.0-4.3) > soil tillage (1.4-6.5) ≥ fungicide
application at anthesis of wheat (1.7-2.7). These data confirm that wheat crop quality
management, aiming at a low DON concentration, must start in the field and first focus on
agronomic factors that influence FHB infection. Above all, conditions such as preceding host
crops, especially maize, which can leave infected residues in the field and the cultivation of a
susceptible cultivar contribute to increase Fusarium infections of wheat crops. These data
confirm the results obtained in France in 7 years of trials by researchers from Arvalis
(Barrier-Guillot et al., 2006; Gourdain, 2008), who obtained a grid with 7 levels of risk for
DON contamination in wheat grains based on 3 combined risk factors: previous crop, tillage
and varietal sensibility to FHB.
4.1. Crop Residue and Proceeding Crops
It is generally accepted that if a wheat crop follows an alternative host for Fusarium
pathogens it is at a greater risk to FHB and DON contamination of grain. All species of
Fusarium are able to survive through the winter as mycelia in non-decomposed residues from
the previous crop, with the subsequent production of ascospores in the perithecia located on
the surface of the pathogen-infested residues (Osborne and Stein, 2007). The primary
reservoir of inoculum is debris from the previous crop (Bai and Shaner, 1994) and pathogens
survive longer on residues that do not degrade easily, such as stem nodes (Sutton, 1982).
Thus, FHB disease and DON contamination are more severe if the preceding crops are maize
or sorghum, rather than wheat or barley and even less contamination is observed following
other crops (Dill-Macky and Jones, 2000; Krebs et al., 2000; Champeil et al., 2004b;
Maiorano et al., 2008).