However, populations of this fungus in Victoria have been exposed to thiabendazole for over two decades. Most of 55 isolates of H. solani from 15 different locations around Victoria were found to be resistant to thiabendazole in recent tests. This means that in many instances thiabendazole will not be effective in controlling silver surf in potato sheds. Resistance Management Strategies Resistance management strategies are critical to the sustainable use of pesticides. Fungicides should be used prudently.
Good practice is to alternate thiabendazole with imazalil treatments each season.
Tank mixtures of both fungicides is another strategy with the added advantage of providing a broader spectrum of activity against a range of pathogens. Registered mixtures containing two different classes of fungicides are available to potato growers in Europe but not, as yet, in Australia. Controls included untreated tubers and disease-free minitubers produced on tissue culture plantlets in glasshouses. The effectiveness of the seed treatments varied with cultivar and location. The relatively high incidence of minituber progeny with black scurf at Ballarat is consistent with higher populations of soil-borne R. solani in old ground compared with new ground.