Soft rot infections may be masking the true extent of dry rot infection in store, seed potato producers were warned at the Seed Industry Event held in Crieff by the British Potato Council (BPC).
BPC plant pathologist Dr Jeff Peters said dry rot, caused by the Fusarium pathogen, is one of the most common fungal rots affecting stored potatoes in the UK with losses estimated at 35,000 tonnes each year.
A three-year study of the disease by the BPC examined around 11,000 tubers between 2001 and 2003 and collected over 200 different dry-rot causing Fusarium isolates. Researchers focused on four common pathogen species and found that two of these, F. avenaceum and F. sulphureum, showed some resistance to the fungicide.
“According to the survey, treating seed with imazalil increased the proportion of F. avenaceum rots,” said Peters. “Similarly, applying thiabendazole (TBZ) to seed increased the level of F. sulphureum compared with either imazalil or nil fungicide.
“Susceptible varieties like Hermes and Russet Burbank need careful monitoring. Some producers are carrying out DNA testing to diagnose the particular Fusarium species to help determine the risk of the rot developing.”
Peters highlighted that in order to manage resistance issues, the industry has worked to secure an emergency off-label use for a tank mix of imazalil and TBZ for the control of dry rot in seed potatoes.
Also dry rot risk is minimised by setting tuber skins, controlling damage and dry curing crops quickly when entering the store.
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