Variation in sensitivity to fungicides which inhibit ergosterol biosynthesis in wheat powdery mildew

Abstract

Fungicides which inhibit ergosterol biosynthesis have been in use for control of wheat powdery mildew (Erysiphegraminis f. sp. tritici) in the Netherlands since 1978. Mildew populations were tested for their variation in sensitivity to triadimefon from 1982 to 1984.In 1982 isolates from the province Limburg, with a triazole spray-regime history, were less sensitive to triadimefon than isolates from the provinces Gelderland and Noord-Brabant, where triazoles had not been used. In the following years isolates with reduced sensitivity were also detected in the latter provinces and other parts of the country. This spread correlates with the increased use of triazoles, both in frequency and space, from 1983 onwards. The reduced sensitivity can as a whole or in part be responsible for the decline in field performance of triazoles, observed during these years.Cross-sensitivity to the triazoles triadimefon and propiconazole was established, but not to triazoles and the morpholine fungicide fenpropimorpb. Effectiveness of the latter compound was similar to all isolates from Limburg tested in 1984. Field performance of fenpropimorph, introduced in 1983, appeared to be normal. It is recommended to counteract further development of resistance by sequential use of fenpropimorph early in the season (May) and triazoles at the end (June-July).

Sequence variation in the CYP51 gene of Blumeria graminis associated with resistance to sterol demethylase inhibiting fungicides

“…Widespread and continued use quickly led to decreased DMI sensitivity in both Bgh and Bgt (Butters et al, 1984;De Waard et al, 1986;Fletcher and Wolfe, 1981;Wolfe and Fletcher, 1981). However, resistance to DMIs evolved gradually in B. graminis.…”

Antifungal Activity of Lower Alkyl Fatty Acid Esters against Powdery Mildews

“…In case of foliar diseases such as powdery mildew, the application of fungicide spray may be the main measure to control the disease in most crops (McGrath, 1996). However, field isolates of powdery mildew fungi being resistant to fungicides such as benzimidazoles (benomyl and carbendazim), DMIs (triadimefon, triadimenol, and flusilazole), and QoIs (azoxystrobin, trifloxystrobin, and pyraclostrobin) have developed rapidly and have become widespread worldwide (De Waard et al, 1986;Fernandez-Ortuno et al, 2006;Fletcher and Wolfe, 1981;Ishii et al, 2001;McGrath and Shishkoff, 2003;Schepers, 1983;Schroedder and Providenti, 1969;Vargas, 1973;Wilcox et al, 2003). Because of concerns about human health and environmental quality, the demand for organic foods cultivated without synthetic fungicide treatment is rapidly increasing.…”

Experimental verification and development of EPIPRE, a supervised disease and pest management system for wheat

“…Furthermore, the economic gains from use of treatment I can be expected to fall in the next years owing to the decline in wheat prices in the European Community and in the efficacy of pesticides. Even the fairly restricted use of ergosterol biosynthesis inhibitors in Dutch wheat growing since 1978 has led to a decreased sensitivity to some of these chemicals in the mildew population within five years (De Waard et al, 1985). On fields sprayed routinely against eyespot, five sprays were sufficient to select for insensitivity.…”