As strawberries come into flower, growers are being recommended to use first conventional then biological controls against Botrytis cinerea - a particular problem in last year's damp weather.
"The sound strategy is to use fungicides early and then rely on biologicals nearer to harvest," said East Malling Research (EMR) fruit pathologist Dr Angela Berrie. "Flowering is the main time when Botrytis gets in."
By starting with Teldor (fenhexamid), alternating with other botryticides to avoid resistance, then switching to biological control Serenade ASO (Bacillus subtilis strain QST 713) close to harvest, growers can achieve control while minimising residues on produce.
Kent soft-fruit grower Alistair Brooks applies Teldor from the white bud stage of flowering alternated with fungicides from the two other chemical classes; Signum (boscalid + pyraclostrobin) and Switch (cyprodinil + fludioxonil).
"Once we're into picking we use Serenade ASO quite a lot - it fits well with the use of weather stations and predictive modelling using the BOTEM system," he said.
The BOTEM computer-based Botrytis warning system, developed by Berrie and others at EMR, enables fungus control with smaller, targeted fungicide applications.
Brooks added: "Biological fungicide gives us zero harvest interval, no restriction on the amount we can use, is safe to biological control predators and has no residues. We are using so many predators that it's vital we have disease-control products that are safe to them."
Serenade ASO Holding up in tough weather
Hutchinsons horticulture technical manager Jonathan Blackman said last year's poor weather provided the toughest test yet for Serenade ASO.
"It held up pretty well and is a useful addition to our armoury, though is best used in combination with conventional fungicides," he said. "It is complimentary to Teldor on everbearers where products with short harvest intervals are vital."
Stocks of Teldor ran out late last year, added Blackman, saying: "That speaks volumes about its vital role in seasons of severe Botrytis pressure."