Impact of fungicide application to control T-2 and HT-2 toxin contamination and related Fusarium sporotrichioides and F. langsethiae producing species in durum wheat

Fusarium Head Blight (FHB) is the main devastating disease of wheat worldwide. Most of the studies are addressed to control the main fungal agent F. graminearum. However, the FHB species composition is wider and influenced by meteorological and agronomic factors, depending on geographical region and, more recently, subjected to the ongoing climate change. Many strategies to control FHB agents in field conditions have been studied. Among these strategies, the fungicide application proved to be among one of the most effective. To date, very poor investigations were carried out to evaluate the effects of fungicides in wheat against F. sporotrichioides and F. langsethiae, the species associated to FHB that produce type A trichothecenes, such as T-2 and HT-2 toxins. The effectiveness of the triazoles, prothioconazole and metconazole, and the strobirulin azoxystrobin, alone and in combination with tebuconazole, was tested in three field trials, two locations and in two growing seasons, in Italy, against F. sporotrichioides and F. langsethiae species, to evaluate their impact on the T-2 + HT-2 contamination in wheat. The trials were carried out by comparing the different fungicide effects, under natural infection and on artificially infected wheat plants. FHB incidence and severity, significantly different between the two geographical locations, were effectively reduced by fungicide application. Similarly, F. sporotrichioides and the positively correlated T-2 and HT-2 amounts, were effectively reduced up to a range of 53-91% under natural infection and 30-70% under artificial infection, depending on the active ingredient. On the contrary, F. langsethiae was effectively reduced by fungicides only in natural conditions, while it appears to be insensitive to fungicide treatments under artificial infection trials. In addition, the artificial inoculation with this species failed to achieve high level of infection. Moreover, qPCR was proved to be among the needful methods to detect F. langsethiae, whose isolation failed by classic mycological method. In this first study on fungicide effectiveness against F. sporotrichioides, F. langsethiae and T-2+HT-2 contamination in wheat plants in field trials, we have demonstrated that triazole compounds are able to mitigate the possible contamination of type A trichothecenes and their producing species. Among the tested fungicides, prothioconazole demonstrated to be the most effective against both fungal species and under all the experimental conditions. On the other hand, azoxystrobin showed to be less effective in presence of high fungal infection.