POTATO crops face a high blight threat according to the British Potato Council (BPC). The recent wet and humid weather plus rapid crop development has created a very favourable microclimate for blight to develop.
"Maintain spray programmes at the minimum intervals during unsettled weather," urges
Nick Bradshaw of the BPC blight advisory team. "Keep checking the situation
in your region by visiting the BPC's blight mapping website (www.potato.org.uk/)."
Mr Bradshaw says: "Blight outbreaks occurring at this stage of the season can be very difficult to control. Spray intervals should not exceed 7 days. Where sprays are delayed, include a fungicide with good 'kick-back' activity and be prepared to re-spray crops where heavy rainfall occurs soon after spraying.
Growers need to achieve good spray cover down through the profile of the haulm canopy to protect the lower leaves, irrespective of the fungicide product being used. This should be taken into account when setting-up the sprayer, adjusting the spray volume and determining ground speed. However, it is important not to compromise spraying capacity and the need to treat crops quickly should weather conditions dictate.
Mr Bradshaw also encourages growers to check outgrade piles, a major source of blight infection. "Where haulm growth was tackled earlier in the season you may need to re-treat."