A new approval for Amistar is set to better protect potato crops from Alternaria that can decimate green leaf area in the summer months.
With Amistar foliar treatments targeted specifically at stopping infections of Alternaria solani spp, growers and agronomists now have a season long programme to help prevent pathogen strains from June through to harvest, advised Douglas Dyas, Syngenta Potato Field Technical Manager.
“Alternaria has been an increasing problem in some recent seasons,” he reported. “The increased area of varieties that are more susceptible to infection, combined with prolonged periods of stressful weather conditions, has led to serious outbreaks in some seasons.”
Douglas advocated that Alternaria must be tackled preventatively, in conjunction with the late blight fungicide programme. “Growers should look to start Alternaria control as soon as conditions are conducive to infection, typically from end of June, but remaining aware of risk factors for any individual crop.”
His recommended programme will incorporate up to three applications of Amistar, aimed at protecting against Alternaria solani, in conjunction with Amphore Plus, utilising its combination of a robust application rate of difenoconazole, to give effective prevention of A. alternata and A. solani, along with its built-in full rate of mandipropamid (Revus) for blight control.
“This approach should be sufficient to offer protection for crops throughout the season,” he advised. “Growers will have to add a blight fungicide with their Amistar treatments, such as Revus or Shirlan, depending on previous treatments and within CAA and FRAC guidelines.”
He highlighted that best results will be achieved where growers use fungicide protection in an integrated crop management (ICM) programme, including variety selection and aiming to avoid high risk stress factors, such as soil moisture or nutrient stress.
A further change to the Amistar approval in potatoes has seen the removal of the overall treatment of seedbeds pre-planting at 6 l/ha. However the 3 l/ha in-furrow application remains unchanged for Black Dot and Rhizoctonia, to improve skin finish, along with enhanced tuber consistency and quality.
Growers with stocks of old label Amistar can still use it to make the 6 l/ha overall application at planting, with a use up of old label material by the end of August 2018. Old label Amistar can also be used for the new foliar Alternaria treatment, but a copy of the authorisation letter must be downloaded from the CRD website before use (www.pesticides.gov.uk).