Watch out for early threat from downy mildew

Growers are being advised to think ahead and plan their fungicide campaigns now, if they want to reduce the threat of downy mildew in their vegetable and salad crops at harvest time.

The risk of downy mildew, and the resulting crop losses, is strongly linked with the type of weather conditions expected over the next few weeks, warns one adviser.

UAP vegetable specialist Chris Wallwork, says that the key thing for growers to do now, is think ahead as to what fungicide options they have available for the duration of the crop's life. "Farmers will know the autumnal feel that brings downy mildew into their crops, but my impression is that, these days, those conditions are becoming more common by late July or early August.

"When the downy mildew weather arrives, growers need to be ready," he says.

"Growers are constantly told to minimise pesticide use and the range of products is also diminishing, which means that they need to be even more targeted with their applications," he adds.

Mr Wallwork suggests that spray intervals can be stretched in low risk periods of dry, breezy weather. Equally important, he stresses, is that too long a delay will leave the crop vulnerable if the disease gets hold. "Ideally, fungicides need to be applied just prior to the high risk weather," he points out.

"Where you have options, try to get a degree of resistance management. Try not to repeat the same fungicide groups, and refer to FRAC guidelines to help identify what is applicable.

It's also important to match the strengths of different products to appropriate stages of crop and disease development, believes Mr Wallwork.

"Downy mildew resistant varieties will help but they will still need treating, depending on the severity of the disease and the variety in question," he comments.

"If downy mildew is present at harvest then it's a real threat to the marketability of salad crops, while vegetables will suffer from reduced yields.

"We know the disease is the next thing to look out for, so the message is to be ready when it comes," concludes Mr Wallwork.