Temperature effects on the development of sweetpotato mottled necrosis caused by Globisporangium ultimum var.ultimum and effective fungicides screening
Sweetpotato mottled necrosis caused by Globisporangium ultimum var.ultimum is a newly reported disease in China.It causes severe yield losses in the end of harvest or early stage of storage.In order to effective-ly control the disease,temperature effect on the pathogen growth and the disease developing were tested in vivo and in vitro,then the toxicities of 10 fungicides to G.ultimum and their control efficacy to mottled necrosis were evaluated.The results showed that the optimum temperature for the growth of G.ultimum on PDA was found to be 30 ℃,while the disease development on sweetpotato roots was optimal at 20 ℃.In the temperature effect test for the toxicities of different fungicides to G.ultimum on PDA,the toxicity of metalaxyl-M·mancozeb was the highest at 15 ℃ among different temperatures tested at 15 ℃,20 ℃,23 ℃,and 25 ℃,while pyraclostrobin and cymoxanil·mancozeb were more effective at 15 ℃ and 20 ℃ compared to higher temperatures at 23℃and 25 ℃.The toxicity of fluopicolide·propamocarb hydrochloride was the lowest at 25℃ among the temperatures test-ed,whereas those for oxathiapiprolin and oxine-copper were not affected by the temperatures.The protective effects for those fungicides were higher than their therapeutic effects in vivo.Both of protective effects and the therapeutic effects of metalaxyl-M·mancozeb and fluopicolide·propamocarb hydrochloride were higher than those of other fungicides tested.
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