Ed Hagues, Bayer root crops campaign manager

The arrival of rain and cooler temperatures has favoured conditions for disease spread with localised cases of rust and cercospora. The BBRO is advising growers to check crops carefully.

With the break in the weather crops are likely to come under increasing pressure. In a typical season most growers would have applied their first fungicide by the end of July, but due to the dry weather conditions have been far from favourable for disease.

“Disease is present in some crops, but pressure is localised. The rain in early August however, has led to a flurry of instances and crops will need monitoring closely until the end of summer,” says Ed Hagues, Bayer root crops campaign manager.

“Powdery mildew has been reported in localised patches, but the weather has been highly effective at keeping rust at bay until recently. Rust comes into the crop every year and the fear now is that growers could be hit with the double-whammy of powdery mildew and rust in equal measure,” he adds.

Despite the dry conditions, the advice to growers remains much the same as in any other season: apply your first fungicide in late July/early August prior to disease onset.

“With the recent rain sugar beet canopies have picked up and sprays have been applied, BBRO advice is quite clear: apply Escolta (cyproconazole + trifloxystrobin) at full-rate as soon as disease is identified with a second application, also at full-rate, four weeks later,” says Ed.

“Trials demonstrate that crops which receive two full-rate applications of Escolta consistently out-yield those receiving other treatments because they fare better heading into the winter,” he says.

In 2017 Bayer trials found that the second application of Escolta at 0.35L/ha added 12t/ha over untreated to December-lifted crops and almost 26t/ha to February-lifted crops. There was high rust pressure through the summer of 2017 and this put greater pressure on the second spray. Opting for a single application or selecting less effective chemistry didn’t give the necessary disease protection.

“Across all lifting dates the average yield response in 2017 for crops receiving two full applications of Escolta was 14.9t/ha, this is worth £335/ha with beet at £22.50/t,” he adds.

A disease which has attracted attention in recent seasons, but which has historically been an infrequently seen disease is cercospora leaf spot. For all its potential to cause yield losses, it should not distract from the principal threat to UK crops: rust, which can result in yield losses of 14%.

“Conditions are hot enough, but not moist enough for cercospora at the moment,” Ed concludes.

Ed Hagues’ five tips for keeping crops free of disease

  • Time the first application prior to disease onset as trials indicate yield potential is best protected where disease is prevented from becoming established.
  • Maintain application rates at the full-label rate. Trials demonstrate that crops receiving two full-rate applications of Escolta do better as they are kept free of disease for longer.
  • Ensure water volumes are sufficient to fully penetrate the canopy. Although likely to be less of an issue this season, experience tells us that all leaves and stems need to receive fungicide to keep disease at bay.
  • Ensure intervals are kept to about 28 days. Trials demonstrate that where intervals are longer than about four weeks it allows disease to get back into the crop.
  • Record where varieties are drilled to understand disease susceptibility and response to fungicides