McCulloch has witnessed high levels of the disease on a range of crops alongside other wet-weather diseases including ring spot, white blister and Botrytis. Although controls are available, McCulloch is concerned about controlling these diseases adequately without increasing resistance risk.
With continuing wet, warm and humid conditions expected, the County Crops agronomist said growers should adopt an appropriate fungicide regime with resistance and crop safety as priorities.
He suggests starting programmes early with a fungicide such as Signum from BASF, which can be mixed with a triazole to be followed by other products with different modes of action to reduce resistance. He said: "Signum gives an excellent start to the programme, being active against all the key lettuce diseases including Sclerotinia, Botrytis and mildew.
"It is usually followed by a metalaxyl-containing fungicide and then Invader - it is important to minimise any resistance pressure on any one fungicide group."