In a past article, I discussed recent research that examined drip application of prothioconazole and thiophanate-methyl for suppressing Fusarium wilt, caused by Fusarium oxysporium f.sp. niveum (FON). Ultimately, this research indicates that application of these fungicides can suppress FON, although they are not silver bullets. We understand little about the effects of these fungicides on different life stages of FON, or the potential for fungicide resistance development in populations of FON to these active ingredients. Thiphanate-methyl in particular, is considered to have a high degree of risk for developing fungicide resistant populations in many fungal pathogens.
Recent work published in the journal Plant Disease addressed these questions in the FON population in Georgia. 100 isolates were collected and tested for fungicide sensitivity. All isolates were sensitive to prothioconazole, whereas 33 % of the isolates were resistant to thiophanate-methyl. Fungicide resistance was associated with a point mutation, meaning that a single nucleotide was altered, resulting in a change to the site targeted by thiophanate-methyl (B tubulin). . This is the first report of isolates of F. oxysporum resistant to thiophanate-methyl. The authors of the work state that prothioconazole may be a viable option for management of Fusarium wilt of watermelon whereas thiophanate-methyl should be used judiciously due to the existence of isolates resistant to the fungicide.
To view the abstract and access the paper, click here.