Growers are being urged to protect lettuce crops against downy mildew or otherwise risk crops unfit for market.
Vegetable consultant Colin Bloomfield is warning that downy mildew (Bremia lactucae) can be particularly difficult to control due to the current weather conditions proving favourable to fungal development.
He said: “The warm days and cool nights are resulting in condensation and dew forming, with leaf wetness a key trigger for downy mildew and spore germination.
“It is one of the top two lettuce diseases, attacking young crops and causing severe stunting, with later stage infections leaving crops unmarketable.”
Bloomfield said that downy mildew reduces marketable lettuce weights - which can mean that a minimum harvest weight of 180g may not be reached.
There are hundreds of known strains of downy mildew, and new races are continually evolving. “Growers need a full complement of 1-26 if not 1-27 resistance in their plant variety to guard against the known races in existence. Curly Charita, which does not have a full complement of 1-26, is one variety which has been badly affected this year,” said Bloomfield.
Growers have the opportunity to incorporate systemic fungicide Aliette 80 WG as a drench within the spray programme against downy mildew under a specific off-label approval (3522/2006). As with any off-label approval, growers are reminded that use of Aliette at the growers’ own risk, according to experts.
Aliette 80WG is the only fully systemic fungicide which can move both up and down within the plant.
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