Fungicide control of mushroom cobweb disease caused by Cladobotryum strains with different benzimidazole resistance profiles

Abstract

The benzimidazole fungicides thiabendazole and carbendazim, and the imidazole fungicide prochloraz-Mn, were tested for their efficacy in controlling cobweb disease of mushrooms caused by two Cladobotryum isolates. Isolate 202A was benzimidazole-sensitive in vitro and cobweb growth on the casing was well controlled by both benzimidazole fungicides in cropping experiments. Carbendazim also controlled the development of spotting symptoms much more effectively than thiabendazole. A second isolate (192B1) was benzimidazole-resistant and was highly resistant to thiabendazole in vitro but it showed some sensitivity to carbendazim in vitro at moderate to high concentrations. Despite this, carbendazim did not control disease symptoms in cropping experiments, confirming that isolate 192B1 is cross-resistant to other benzimidazole fungicides. Both isolates showed some sensitivity to prochloraz-Mn in vitro. This fungicide gave between 45% and 65% control of cobweb growth on the casing caused by either 202A or 192B1 but gave no control of spotting symptoms. Reducing the fungicide application volume did not give enhanced disease control. The emergence of benzimidazole resistance reduces the value of benzimidazoles in the control of mushroom pathogens. However, the lack of effective alternatives means they continue to have utility in cases where pathogens are still sensitive but this requires regular monitoring of pathogen populations for resistance.

Cobweb, a serious pathology in mushroom crops: A review

“…causes two types of cap spotting on infected mushrooms, dark-brownish spotting with an ill-defined edge and grey-yellowish spotting (Grogan & Gaze, 2000;Grogan, 2006) (Fig. 2c,d).…”

“…In view of this, control of the pathology still relies on the use of chemical fungicides. However, since the sensitivity of mycoparasites to approved pesticides is gradually diminishing and signals of resistance have been detected (McKay et al, 1998;Gea et al, 2005;Grogan, 2006), their use demands judicious management. In short, to optimize integrated disease control, the use of chemicals must be combined with good farming practices and with measures directed towards enhancing hygiene within growing facilities.…”

Identification and control of Cladobotryum spp., causal agents of cobeweb disease of cultivated mushroom

“…su iznosile 0,1-7,8 mg/l, što je ukazivalo na povećanje tolerancije patogene gljive na ovaj fungicid (Grogan i Gaze, 2000). Grogan (2006) je utvrdila da prohloraz-Mn omogućava zaštitu A. bisporus od pojave paučinaste plesni 45-65% u oglednom gajilištu, međutim, ovaj fungicid nije sprečavao pojavu smeđih mrlja na šeširima plodonosnih tela. Autor ističe da se i pored smanjenja efikasnosti, prohloraz-Mn i dalje preporučuje za primenu u suzbijanju Cladobotryum spp., jer je patogen još uvek osetljiv, s tim da je neophodno redovno praćenje osetljivosti u populaciji patogena na ovaj fungicid.…”

“…godine u Srbiji (EC 50 <0,1 mg/l) (Potočnik i sar., 2009a). Iz ove grupe fungicida u gajilištima A. bisporus su primenjivani triadimefon u Indiji (Sharma i Kumar, 2005) i pirifenoks u Velikoj Britaniji (Grogan, 2006). Ovi fungicidi su po navodima autora ispoljili zadovoljavajuću efikasnost u suzbijanju Cladobotryum spp.…”

In vitrotoxicity of selected fungicides from the groups of benzimidazoles and demethylation inhibitors toCladobotryum dendroidesandAgaricus bisporus

“…[11−14] Prochloraz manganese is the most effective fungicide in prevention of Cladobotryum spp., but it has been found no longer able to control the spotting symptoms of cobweb disease. [15] Benomyl, carbendazim, thiophanate-methyl and prochloraz manganese are frequently applied in Serbian mushroom farms, while thiabendazole, which is a popular fungicide in Europe, is not registrated in Serbia. [4] Since resistance to MBC fungicides has developed and the number of available fungicides is decreasing, carbendazim, prochloraz manganese and chlorothalonil are still officially recommended for mushroom cultivation in EU countries.…”