With a high incidence of gout fly this season, growers are being advised to plan ahead to avoid problems in 2017 crops.
This season, Roy Workman’s 162-hectare (400-acre) mixed farm in Gloucestershire has been hit hard by gout fly. In fact his agronomist, Stephen Earl of Agrii, says it is the worst gout fly he has seen in 40 years.
Having never before seen the pest on his land at Cape Hall Farm, near Gloucester, Mr Workman had no reason to look for it and it was not until February he realised the severity of the problem.
He says: “We spotted the infestation in mid-February. Before then the crop looked absolutely fine and had been treated with a post-emergence herbicide and a pyrethroid insecticide.”
See also: Winter wheat shows promise
Unfortunately, the infestation took hold and Mr Workman had to take the decision to spray off the worst-affected field and replace the wheat with maize for his Aberdeen-Angus cattle. However, some of the gout fly-infested wheat elsewhere on the farm has recovered, he adds.
“In the worse-affected field only 50 per cent of the tillers were left and the infestation was from corner to corner, so it was not worth investing in its recovery," says Mr Workman.
“In terms of insecticides, a balanced approach would be to use a seed treatment to protect against both BYDV and gout fly, and use a follow-up insecticide spray six to eight weeks later.
“Deter (clothianidin) is one of the best seed treatment options available. Its activity against gout fly is ‘off the label’, but it has been proven in field trials to provide protection for the initial six to eight weeks from drilling.
“However, we decided to have one more roll of the dice with one of the fields. This field is the most fertile on the farm, with the best soil and is the easiest to manage. It has JB Diego in it as a second wheat and while it has recovered well, it is very uneven in height and the size of its ears varies quite a lot.”
In this same field last season Mr Workman achieved a winter wheat yield of 11t/ha (4.5t/acre), but following the gout fly infestation he is expecting his yield to halve this harvest.
According to Mr Earl, prevention rather than cure is the best approach when it comes to gout fly. Cultivations will not prevent infestation, but there are other management and insecticide options available, he says.
“Earlier drilling of wheat leaves the crop susceptible to attack from the autumn adults. Indeed, on Mr Workman’s farm the wheat drilled in late October had very little gout fly infection, compared to that drilled in late September. So later drilling is certainly something to consider if your crops are at risk from gout fly.
"If you have not dressed your seed, then pyrethroid Hallmark Zeon is another option, but the timing of spraying has to be very accurate to see a yield response.“
Mr Workman will now need to consider how to ensure his crops are not infected with gout fly next season, adds Mr Earl.
“If there are signs of gout fly in the crop this season, then you certainly should use an effective seed treatment to protect your crops.
"Prevention, rather than cure, has to be the preference as once the larvae are in the shoots all you can do is apply nitrogen and hope the crop recovers.”