ADAS plant pathologist Kim Green told the Asparagus Growers' Association conference at Warwick HRI, Wellesbourne, earlier this month that the work had found that spores of the Stemphylium fungus were not killed by being buried, but were prevented from being released from their spore cases to start new infections.
"Debris management is key to breaking the cycle," she said.
Some growers have tried propane burners, which are useful for small areas but uneconomic on a large scale. Rye grass mulches have also been employed in the US to prevent soil blow.
"This could help to reduce disease severity but is unlikely to eliminate the disease if you have got the right conditions for it to develop," Green added.
Chemical control relies on protecting the fern over a four- to five-month period. "Yield losses still occur," she said. "The disease is sporadic so a prophylactic [preventative] spray programme is unlikely to be cost-effective."
Fungicide programmes and better ways of dealing with debris will be evaluated in a new HDC project that starts next month.
An American-developed forecasting system, called Tom-Cat, will also be trialled to see if it is suited to UK conditions.
Invented originally for field tomatoes, Tom-Cat is being used by US asparagus growers to predict the best time to apply sprays by measuring periods of leaf wetness and average air temperature during those stages - factors that influence spore germination.
Green pointed out: "The advantage is that sprays would only need to be applied when conditions are high risk."