Study on the chemical control of wet bubble disease of Agaricus bisporus

Nowadays, mushrooms as one of the agricultural products are in the center of public attention in production, nutrition and income points of view and their cultivation and production are increasing day by day around the world including Iran. This product like other agricultural products are susceptible to some dangerous diseases that can seriously threaten its production. Two similar fungal diseases called dry bubble and wet bubble with the causal agents of Verticillium fungicola and Mycogone perniciosa respectively, attack button mushrooms (Agaricus bisporus). In summer 2001, symptoms of the above mentioned diseases were appeared with a wide range scale in mushroom cultivation centers in Iran. At the beginning, the producers suspected wet bubble disease mostly and therefore the research project was conducted toward this disease but in practice dry bubble disease caused by V. fungicola was detected as the serious problem in mushroom cultivation centers. In this study, six production centers were visited during different time periods specially June, July and August and after collection of samples, isolation of possible disease causal agents was carried out. A total of 50 fungal isolates were isolated that morphological characteristics of most of them corresponded with those of V. fungicola. Of these isolates, 10 were selected and were tested in a pathogenicity test in a mushroom cultivation center. Based on the results obtained. isolate V.f. 8 which was the most virulent was selected for further studies. In continued studies during 2002 and 2003 the efficacy of fungicide Sporgon (WP 50%) was investigated in comparison with two commonly used fungicides, Benomyl (WP 50%) and Carbendazim (WP 50%) respectively in a completely randomized blocks experiment with two control treatments and five replicates (blocks). Forty five plastic bags containing compost inoculated with mushroom seeds and covered with soil under cultivation condition were randomly located on a bench in greenhouse according to the plan and their covering soil were immediately sprayed with a suspension of V. fungicola spores with a concentration of 6x 10 5 ml -1 . Nine, 21 and 35 days after covering bags with soil, test fungicides were applied on covering soils. After the appearance of the mushroom caps, the weight and the number of healthy caps in each replicate was recorded separately. Analysis of data using Duncan,s Multiple Range test showed that there were significant differences among treatments in disease incidence at 1% level in both years. Sporgon was the most effective fungicide against dry bubble disease at 0.9g/m 2 which was applied 9 days after covering bags with the soil. Compost bags which were treated with Benomyl and Carbendazim produced the least number of caps.