Look out for dry rot in potatoes

Potato growers and seed producers need to be on the look out for signs of dry rot and be prepared to act to minimise the threat of the disease developing, the British Potato Council has advised.

The disease affects around 1% of tubers annually and varieties such as Hermes, Estima and Maris Piper are especially susceptible, said BPC plant pathologist, Jeff Peters.

“Seed suppliers should be assessing the likelihood of rot developing in their stocks. Ware growers should consider the risk of rot when they source their seed.”

Risk of dry rot can be reduced by “hot-boxing” samples at temperatures above 10oC to create an environment for the disease to exhibit itself, he said. Where treatment is needed, he recommends a tank mix of imazalil and thiabendazole.

Seed growers should also aim to grade stocks once as the store is loaded to reduce the risk of bruising and spreading contaminated dust, he added.

While it is too early to tell whether dry rot incidence is higher than normal this year, disease incidence tends to be higher in high damage years, added BPC storage campaign manager, Kate Jackson.

“Growing conditions that increase the risk of dry rot are warm, sandy soils, volunteer problems and a warm, dry season. In store, the risk can be increased by poor curing (wound healing) and holding at high temperatures.”

Help with identifying and assessing dry rot risk is available in the new BPC dry rot risk assessment guide, she noted. Email publications@potato.org.uk for a copy, or call the free Storage Advice line on 08000 282111 for specific storage queries.