With high disease pressure, a high percentage of susceptible rust varieties in the ground plus high crop values, a T0 spray is needed and will be worthwhile in most wheat crops. Including the protectant fungicide mancozeb at this critical timing will give valuable benefits over straight chlorothalonil. Mancozeb can be delivered to the crop either as a straight product as Quell Flo or as a coform with chlorothalonil in Guru, both flowable products having recently been re-registered with new data for wheat disease protection.
Agronomist Andy Scott of LW Vass is using the coformulation Guru at T0 timing as he believes it has a number of advantages over chlorothalonil alone, including better yellow rust and brown rust control. "Chlorothalonil offers good protection against Septoria, but so does mancozeb, but mancozeb also offers protection against yellow and brown rusts. Both actives are strong protectants and both are multi-site, important when it comes to disease resistance management. Mancozeb is active at least 6 different sites within the fungus."
"The T0 spray needs to protect against Septoria and yellow rust but it also buys you time when it comes to the T1 timing in April. What is required is a cost-effective, broad-spectrum treatment to start the programme off and Guru will certainly tick all those boxes. In addition the mancozeb component provides additional "free" manganese available to the plant, making leaves greener and leading to improved photosynthesis," points out Andy.
Dr David Stormonth of Interfarm UK confirms that new efficacy data from the re-registration packages shows that the disease spectrum controlled by mancozeb extends beyond Septoria protection to include control of yellow rust, brown rust and powdery mildew and ear diseases.
"In trials 1.5 L/ha of Quell provided levels of control of Septoria tritici similar to 1.0 L/ha of chlorothalonil. But when it came to yellow rust, Quell Flo gave almost twice the level of control to that seen from chlorothalonil. When it was mixed with a triazole, yellow rust control for the straight triazole was 90% whereas a tank mix of triazole plus mancozeb gave 95% control. This is an important consideration when you consider the amount of yellow rust already being seen in the field," David says.
The re-registration of Quell Flo and Guru means that growers have a choice to integrate effective multi-site fungicides into their disease programmes and be assured of strong protection against the key diseases and not just Septoria, concludes Dr Stormonth.
