Protect potato tubers against blight infections from tuber initiation onwards, warns Gowan Comercio technical director John Edmonds.

“Once tubers start to form they are at risk from tuber blight.”

Tuber blight is caused by zoospores that are washed down from foliar disease infections, he explains.

“They then cause infection by germinating near to the tuber and entering through access points such as buds, lenticels and wounds.

“The fungus then spreads and starts to break down cellular tissue.

“You only need a few zoospores to reach potato tubers to suffer significant and damaging blight infections.

“Symptoms are usually seen within one month of lifting, but the disease must be prevented in the field well before it gets into store.”

The key is using blight fungicides with zoospore activity, but they need to be used in the correct way, he says.

Using a product such as Electis (zoxamide) stops formation and release of zoospores, but this should be followed by fungicides such as fluazinam, cyazofamid or fluopicolide + propamocarb that act on released zoospores, says Mr Edmonds.

Don’t rely on foliar blight protection alone, particularly when blight pressure is high, he adds.

“Spray intervals should be kept tight right up to and beyond desiccation.”