Look out for signs of Sclerotinia and Alternaria in carrot crops and be prepared to spray before the canopy closes in, growers have been advised.
The first Sclerotinia spore germination in carrots was identified in Norfolk last week (23 June) and although dry weather has minimised the risk of disease development, irrigated crops or low-lying areas of fields may still be at risk, said John Birkenshaw of ADAS.
“Growers must inspect crops closely at the base of the leaves and stems, for any early signs of infection. Once disease gets into the crop, it is difficult and far more expensive to fix.”
An application of Amistar Top (difenoconazole + azoxystrobin) can be effective in controlling both diseases, added Syngenta’s Jon Ogborn, but timing and nozzle choice is crucial.
“For earlier applications growers need to target spray application at the foliage – ideally using air-induction nozzles and applying at a water volume of 100 litres/ha to maximise leaf coverage.
“As the season progresses, switching to 65-80 degree vertical flat fan nozzles and increasing water volume will help spray penetration and enhance basal Sclerotinia control.”
Warm conditions have also triggered the development of Turnip Moth eggs and larvae – giving an indication of cutworm activity, ADAS has warned.
Unless carrot, potato, sugar beet and other susceptible crops receive at least 10mm of irrigation, or heavy rain within the next few days, an insecticide treatment is predicted for early July in southern and eastern England.