**4. Preharvest mitigation measures and management**

One of the main wheat diseases associated with mycotoxin contamination is *Fusarium* head blight (FHB) caused by several species of *Fusarium* fungi, mainly *Fusarium graminearum, Fusarium culmorum,* and *Fusarium avenaceum.* The control of infection by *Fusarium* fungi in field is the first critical step in mitigating mycotoxin accumulation in the harvested products. To reduce the risk of *Fusarium* fungi and mycotoxin contamination, the most important pre‐ harvesting strategy is the application of appropriate good agriculture practices, such as crop selection, crop rotation, tillage, irrigation, and the proper use of chemicals [53].

*Crop selection:* The use of genetic varieties more resistant to *Fusarium* sp. represents an effec‐ tive management strategy to mitigate the mycotoxin challenge in wheat. There are differences in the susceptibility of wheat variety to *Fusarium* and differences in the degree of mycotoxin contamination. Moreover, differences between crops appear to differ between countries which can be related to differences in the genetic pool within each country and the different environ‐ mental and agronomic conditions in which crops are cultivated [48]. Wheat lines have been produced and provide good resistance to *Fusarium* sp. [55, 56]. For an important impact in terms of wheat security and safety, breeding for resistance must provide good resistance to *Fusarium* sp. without adversely affecting quality and agronomic properties. In addition to breeding programs, the increase in *Fusarium* resistance through developing genetically modi‐ fied plants is another approach. It is well documented that transgenic resistance against toxi‐ genic fungi or their toxins may be improved by using three basic strategies: enhance resistance to insect attack, induce mycotoxins detoxification pathways, and reduce mycotoxin accumu‐ lation by interfering with the biosynthetic pathway [57]. The topic of breeding for resistance and transgenic resistance would require a full manuscript. These topics have been specifically and extensively reviewed by several Authors to which the reader is directed [58, 59]. Despite progress made in prevention through breeding of resistant varieties and improvement in agro‐ nomic practices [31, 57], hazardous concentrations of mycotoxins may further occur as a result of annual weather fluctuations.

plants in the field to mold and determine the severity of mycotoxin contamination [5, 31, 53]. *Fusarium* sp. are generally associated with a cool and excessively wet growing season [31, 54]. Wheat storage and processing are the major areas where contamination can be managed and mitigated at postharvest level, keeping in mind that postharvest contamination is also the result of preharvest presence of fungal contamination. The main strategies that need to be considered and implemented to mitigate mycotoxin accumulation pre‐ and postharvest are

**4. Preharvest mitigation measures and management**

One of the main wheat diseases associated with mycotoxin contamination is *Fusarium* head blight (FHB) caused by several species of *Fusarium* fungi, mainly *Fusarium graminearum, Fusarium culmorum,* and *Fusarium avenaceum.* The control of infection by *Fusarium* fungi in field is the first critical step in mitigating mycotoxin accumulation in the harvested products. To reduce the risk of *Fusarium* fungi and mycotoxin contamination, the most important pre‐ harvesting strategy is the application of appropriate good agriculture practices, such as crop

**Figure 3.** More consolidated and emerging strategies to reduce mycotoxigenic fungi and mycotoxin contamination in

selection, crop rotation, tillage, irrigation, and the proper use of chemicals [53].

summarized in **Figure 3**.

232 Wheat Improvement, Management and Utilization

wheat.

*In field management:* Appropriate field management practices may be effective to mitigate mycotoxin contamination in wheat [60]. When crop rotation is considered, maize should be avoided in the rotation, as maize is very susceptible to *Fusarium* sp. and the presence of maize residues appears to be an important factor contributing to DON contamination of wheat [57, 61]. The incidence and severity of *Fusarium graminearum* and DON contamination levels are higher in wheat grown after maize or wheat compared with wheat grown after soybeans [61, 62]. Moreover, the great differences in the frequency of isolation of *Fusarium* sp. and *F. graminearum* among years suggest the importance of annual climatic conditions in promot‐ ing the colonization and survival of these fungi. Other studies found no evidence that wheat following wheat is more at risk than wheat following a non‐cereal crop, since some patho‐ genic *Fusarium* species isolated from cereals can also have pathogenicity toward non‐cereal crops [63, 64]. The incidence of *F. avenaceum*, which is another of the most commonly isolated *Fusarium* species from FHB‐infected ears of wheat in Canada, was lower in wheat grown con‐ tinuously compared to wheat grown in crop rotation [65]. Crop rotation in conjunction with tillage techniques may further mitigate *Fusarium* and mycotoxin contamination. Higher levels of *Fusarium* and DON contamination in wheat have been reported with minimum tillage or no‐till compared to conventional tillage [61, 63]. This effect can be attributed to inoculum sur‐ vival and the concentration of *Fusarium* sp. in the soil [66, 67]. However, not significant effect of tilling has been reported when wheat was grown after soybeans [60].

Irrigation management is another critical point to mitigate preharvest mycotoxin contamina‐ tion. All plants in the field need adequate water supply. Drought stress and also an excess irrigation are favorable conditions for *Fusarium* infection. Drought stress should be avoided during the period of wheat seed development and maturation; therefore, crop planting should be timed accordingly. Excessive moisture in irrigated wheat fields during flowering and early grain fill period is a favorable condition for *Fusarium* infection [68, 69]. Nevertheless, the effect of moisture in increasing the levels of DON contamination is not consistent among published studies [69–73].

*Use of chemical and biological compounds:* Mold infection can be controlled by the appropriate use of fungicides. Fungicide treatment reduces wheat *Fusarium* infection and DON contamination [74–76]. Recently, Scarpino et al. [77] reported that azole fungicides, the most effective active substances in the reduction of DON, also consistently reduce the main emerging and modified mycotoxins of winter wheat in temperate areas. However, as far as the effectiveness of fungi‐ cide application to control mycotoxin contamination by *Fusarium* species, conflicting evidence has been reported. A meta‐analysis carried out by Paul et al. [78] reported results ranging from no detectable effects to substantial reduction in both *Fusarium* head blight and DON with tri‐ azole‐based fungicides. Overall results indicate that the variability of fungicide effects is related to several factors, such as cultivar resistance, the type of fungicide used, fungicide timing, patho‐ gen aggressiveness, and different environmental and agronomic conditions. A greater fungicide efficacy in reducing FHB and DON has been reported in moderately resistant cultivars than in susceptible ones [79]. These results confirm that the efficacy of each mitigating approach must be considered within an integrated strategy for an effective management of *Fusarium* and mycotoxin control in wheat. As a tool of chemical control, several aromatic plant essential oils have been tested for their antibacterial and antifungal properties [80–83]. Results demonstrated a different antifungal activity and efficacy of these compounds, but more research is needed on this topic.

The chemical control of fungal infection and mycotoxin contamination may be only partly effective; therefore, biological control as an additional strategy has been considered and evaluated [53]. The efficacy of bacterial and fungal antagonist against *Fusarium* sp. has been reported in vitro, in the greenhouse, and in the field [84–92]. Biological antagonists can be sprayed directly at the flowering stage to limit the growth of fungal toxin producers. Wegulo et al. [53] concluded that the application and efficacy of the biological control for *Fusarium* infec‐ tion and mycotoxin control pose challenges similar to those posed by fungicide application.

The use of biological control strategies to reduce mycotoxin challenge in wheat can be espe‐ cially useful in organic production where synthetic fungicides cannot be used. The increased demand for organically produced food asks for scientific assessments of the safety of products from different farming systems, such as organic *vs.* conventional. Brodal et al. [93] published very recently an extensive review of studies comparing the content of DON, HT‐2+T‐2 toxins, ZEA, NIV, OTA, and fumonisins in cereal grains from organic and conventional farming sys‐ tems. Inconsistent results have been reported regarding the DON, ZEA, NIV, and T‐2+HT‐2 content in wheat from the two farming systems (**Figure 4**).

Although no significant differences have been found in the majority of mycotoxin compari‐ sons, several studies showed a tendency of a lower mycotoxin content in organically than in conventionally produced wheat. Moreover, results indicate that organic systems appear generally able to maintain mycotoxin contamination at low levels, despite no use of fungi‐ cides. The inconsistency of the results confirm that several preharvest factors, such as those previously described, may have more influence on the mycotoxin levels than the type of farming.

grain fill period is a favorable condition for *Fusarium* infection [68, 69]. Nevertheless, the effect of moisture in increasing the levels of DON contamination is not consistent among published

*Use of chemical and biological compounds:* Mold infection can be controlled by the appropriate use of fungicides. Fungicide treatment reduces wheat *Fusarium* infection and DON contamination [74–76]. Recently, Scarpino et al. [77] reported that azole fungicides, the most effective active substances in the reduction of DON, also consistently reduce the main emerging and modified mycotoxins of winter wheat in temperate areas. However, as far as the effectiveness of fungi‐ cide application to control mycotoxin contamination by *Fusarium* species, conflicting evidence has been reported. A meta‐analysis carried out by Paul et al. [78] reported results ranging from no detectable effects to substantial reduction in both *Fusarium* head blight and DON with tri‐ azole‐based fungicides. Overall results indicate that the variability of fungicide effects is related to several factors, such as cultivar resistance, the type of fungicide used, fungicide timing, patho‐ gen aggressiveness, and different environmental and agronomic conditions. A greater fungicide efficacy in reducing FHB and DON has been reported in moderately resistant cultivars than in susceptible ones [79]. These results confirm that the efficacy of each mitigating approach must be considered within an integrated strategy for an effective management of *Fusarium* and mycotoxin control in wheat. As a tool of chemical control, several aromatic plant essential oils have been tested for their antibacterial and antifungal properties [80–83]. Results demonstrated a different antifungal activity and efficacy of these compounds, but more research is needed on this topic.

The chemical control of fungal infection and mycotoxin contamination may be only partly effective; therefore, biological control as an additional strategy has been considered and evaluated [53]. The efficacy of bacterial and fungal antagonist against *Fusarium* sp. has been reported in vitro, in the greenhouse, and in the field [84–92]. Biological antagonists can be sprayed directly at the flowering stage to limit the growth of fungal toxin producers. Wegulo et al. [53] concluded that the application and efficacy of the biological control for *Fusarium* infec‐ tion and mycotoxin control pose challenges similar to those posed by fungicide application.

The use of biological control strategies to reduce mycotoxin challenge in wheat can be espe‐ cially useful in organic production where synthetic fungicides cannot be used. The increased demand for organically produced food asks for scientific assessments of the safety of products from different farming systems, such as organic *vs.* conventional. Brodal et al. [93] published very recently an extensive review of studies comparing the content of DON, HT‐2+T‐2 toxins, ZEA, NIV, OTA, and fumonisins in cereal grains from organic and conventional farming sys‐ tems. Inconsistent results have been reported regarding the DON, ZEA, NIV, and T‐2+HT‐2

Although no significant differences have been found in the majority of mycotoxin compari‐ sons, several studies showed a tendency of a lower mycotoxin content in organically than in conventionally produced wheat. Moreover, results indicate that organic systems appear generally able to maintain mycotoxin contamination at low levels, despite no use of fungi‐ cides. The inconsistency of the results confirm that several preharvest factors, such as those previously described, may have more influence on the mycotoxin levels than the type of

content in wheat from the two farming systems (**Figure 4**).

studies [69–73].

234 Wheat Improvement, Management and Utilization

farming.

**Figure 4.** Mycotoxin contamination (µg/kg) in wheat from organic (‐ ‐ ‐) and conventional (—) production (W: with fungicide; WOF: without fungicide) (modified by Ref. [93]).

To conclude, there are several preharvest practices and management approaches to reduce the risk of mycotoxin contamination in wheat, whose combination in an integrated strategy repre‐ sents the best mitigation measure. All preharvest practices can be controlled, while climatic and environmental conditions cannot. Computer models, integrating field parameters and weather variables (temperature, rainfall, and moisture level) have been developed to predict the occur‐ rence and risk of *Fusarium* and mycotoxin contamination in wheat [94–98]. Moreover, forecasting systems have been developed to optimize the use and application of chemical treatments [53].
