Growers are being warned to select blight fungicides to suit the stage of crop growth to help combat the more aggressive strains expected to dominate this year.
They are being urged to consider programmes in two distinct phases; the rapid growth phase up to canopy complete and the stable canopy phase thereafter.
Bayer CropScience product manager Neil Thompson said: “Selecting products with the right mobility and activity to suit these distinct phases of growth optimises the use of different chemistry and can make a big difference to blight control.
“During rapid canopy growth, when the crop is building new stem and leaf tissue daily, it needs systemic protection. Phenylamide and propamocarb-based fungicides are the only types listed in the Euroblight table as providing systemic mobility. But all the testing of Blue 13 isolates in Europe so far has shown resistance to phenylamide chemistry,” he warned.
Propamocarb-based fungicides are unaffected by this, Thompson explained, so products Consento, Merlin, Prompto or Tattoo will provide the reliable systemic protection needed during rapid canopy growth.
He said: “When the canopy is almost complete and crops are starting to flower and initiate tubers, it is time to switch to products with tuber blight activity.
“The source of tuber blight is spores washed down from leaves and stems by rainfall and irrigation. So preventing tuber blight requires use of fungicides that will eliminate these infection sources before they can reach the soil. The combination of fluopicolide and propamocarb in Infinito provides the strong anti-sporulant activity needed.”
Infinito gained the highest overall rating of all the products compared at te Euroblight network’s Hamar blight workshop in October 2008 and received the maximum possible score for tuber blight effectiveness.
Thompson said: “Blue 13 is a far more aggressive strain and more damaging to leaves and tubers than the blight we have been used to in the past.”
He recommends using Infinito at 1.6 litre per hectare from canopy complete onwards this year and not stretching spray intervals beyond seven days.
Under high blight pressure, moving to a block of three Infinito sprays should build up a solid foundation of tuber protection.
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