Multisite chemistry offers low risk of resistance Effective use of multisite chemistry and optimising oilseed rape yields were the main focus of a spring crop protection briefing by Adama. Dominic Kilburn reports. Multisite chemistry should be a key part of a spring fungicide campaign in wheat on which to build protection against disease. Not only will it enhance protection against key diseases such as septoria and yellow rust from the start of the programme, but also it will help reduce resistance selection pressure on the main triazole and SDHI products. Those were the key messages from Adama technical specialist Andy Bailey (left), talking at a spring crop protection briefing staged by the company just prior to Christmas. Mr Bailey said that, following the good conditions experienced by many growers in the autumn, the potential was for thick and advanced crops, even those that were later drilled, and so there was likely to be a greater need to start spring fungicide applications early and with robust doses as appropriate. He emphasised that by getting applications on at the right time in the spring, growers would be able to keep crops in “protection mode” through until T2. “It’s been well documented about the efficacy loss of key triazoles in a curative situation against septoria, so it’s a situation growers must avoid crops getting in to. “There’s also erosion in azole activity in protecting against septoria – so it’s a case of trying to slow this slide in efficacy and trying to preserve azole activity as long as possible,” stressed Mr Bailey, who added that recent septoria resistance to SDHIs identified by researchers in laboratories, was also a major wakeup call for the industry. He said that the inclusion of multisite chemistry such as folpet (as in Arizona or Phoenix), chlorothalonil (CTL) or mancozeb at T0 and T1 was critical before disease infects new growth. “Multisites, due to their mode of action, are low risk for resistance and using a product like folpet at T2 is also good management practice,” he added. Mr Bailey highlighted that early conclusions in modelling studies carried out between 2013–2016
have demonstrated that folpet had the potential to double the life expectancy of fungicides like epoxiconazole, which were at high risk to resistant strains of septoria. “In field sensitivity trials, folpet decreased the septoria resistance selection pressure on epoxiconazole compared with when the triazole was applied on its own,” he added. A decrease in selection pressure
The inclusion of multisite chemistry is critical before disease infects new growth.
was also seen when folpet was mixed with SDHI Vertisan (penthiopyrad) + prothioconazole, however it was not so obvious as that seen with epoxiconazole. In other laboratory-based trials
performed by the Silsoe Spray Applications Unit, the addition of folpet to a triazole application enhanced the product’s uptake by the crop. “It’s known that CTL can interfere continued over...
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