Wednesday, 29 February 2012

Multi-site T0 treatment with no antagonism

The warmer winter, advanced lush crops, high disease inoculum and the high percentage of rust-susceptible varieties being grown mean that most wheat growers will be applying a T0 spray this year and the inclusion of the powerful multi-site protectant mancozeb at this early timing will deliver additional benefits over chlorothalonil and folpet.

“Usually applied from mid March onwards, the early T0 spray needs activity against Septoria and yellow rust. 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 Quell (which contains mancozeb) at just 1.5 l/ha plus a triazole will certainly tick all those boxes and more. In addition Quell is non-antagonistic to other fungicides and provides “free” manganese, leading to improved photosynthesis making leaves greener, which boosts growth,” points out Dr David Stormonth of Interfarm UK.

David confirms that efficacy data from recent re-registration proves that the disease spectrum controlled by mancozeb extends beyond Septoria protection to include effective protection from yellow rust, brown rust, powdery mildew and ear diseases.  “Chlorothalonil and folpet offers good protection against Septoria, and so does mancozeb. However mancozeb offers better protection against yellow and brown rusts. An important multi-site product, mancozeb is active, and is known to work at more than 6 different biochemical sites within the fungus.”

“One topical issue is that mancozeb is not antagonistic when mixed with triazoles. Many agronomists have noticed antagonism when chlorothalonil is mixed with triazoles, slowing down uptake and reducing efficacy.  This has not been the case for mancozeb,” he says.
He explains that this difference can be explained by fundamental differences in leaf surface distribution and interaction of the two materials.  “The relatively lower water solubility and higher log P means that chlorothalonil comes out of spray solution quicker and initially binds more strongly to the leaf surface, presenting a barrier to entry of other active ingredients. The high quality formulation of mancozeb in Quell redistributes on the leaf surface more evenly before binding, resulting in a thinner more even coating. Importantly, through vapour activity mancozeb protects areas of the leaf beyond the visible areas of fungicidal deposits. An area more than twelve times greater than the initial droplet size is subsequently protected.”

“In trials a treatment of 0.5 l/ha of epoxiconazole and 0.75 l/ha of chlorothalonil resulted in a yield decrease of 2.5%, whereas 0.5 l/ha of epoxiconazole with 1.5 l/ha of Quell Flo resulted in a yield increase of 11% over the untreated. This indicates the positive impact that mancozeb has when mixed with a strong triazole partner, an additive effect rather than an antagonistic one,” David says.

Dr Stormonth points out that, with the 50th ‘Golden’ anniversary of mancozeb registration, this multi-site fungicide is still going strong, with no fears or any evidence of resistance. Rated in the HGCA’s wheat disease management guide as suitable for resistance management, Quell Flo provides consistent multi-site protection and is suitable for wheat growers in the continuing battle against Septoria.

“It can help protect the long term sustainability of other fungicides with single site activity and we advise growers to integrate it into their disease programmes at T0 timing to be assured of strong protection against the key diseases and a lowered risk of resistance developing,” concludes David.

Dr. Stormonth reminds growers that Quell Flo can be used throughout the programme from T0 to T3.  The standard dose of 1.5 l/ha can be used repeatedly throughout the programme up to grain watery ripe stage (GS73) and the maximum total crop dose is 9.9 l/ha.
For further comment and information, please contact Dr. David Stormonth, Technical Manager, Interfarm UK Ltd. on 01354 741414 or 07818 036506 (mobile) or via e-mail