Outbreaks of frit fly damage are being reported by ProCam agronomists in different parts of the country in winter cereal crops planted after spring oats.

More typically a problem in winter cereals grown after grass, spring oats are also a highly susceptible host to frit fly, says Herefordshire-based Paul Fisher, one of the ProCam agronomists reporting elevated levels of damage.

He believes a rise in the popularity of spring oats, particularly last season in fields where growers struggled to establish autumn crops, coupled with a reduced armoury of insecticides, has allowed the pest to thrive.

Mr Fisher says: “The area of spring oats rocketed last season after growers were unable to plant winter cereals. In my area, around one in eight fields was planted with oats.

“The stage becomes set for damage to autumn cereals when adult frit flies lay their eggs in the developing heads of susceptible host crops over summer. These ultimately give rise to a generation of maggots or larvae on the ground after harvest, which burrow into and feed on the main tiller of the newly-planted autumn cereal soon after emergence.

“Damage is often seen as yellow or red dying or dead shoots in bands across the field that correspond with the combine swaths. Around 50% of winter cereal plants can be lost in these areas,” he adds.

Although little can be done once winter cereals are damaged, Mr Fisher says ensuring a good supply of micro and macro-nutrients and using bio-stimulants to boost growth can help to compensate for tiller losses, provided these are applied in good time.

Where spring oats are to be grown next spring, he urges timely sowing to encourage good establishment and a harvest date that then allows time for cultural control of the volunteers.

Mr Fisher says: “Other cultural methods to reduce the risk of damage in autumn-sown cereals include adjusting drilling dates to allow time for the larvae from the previous crop to die off. Ploughing is also an advantage and early removal of volunteer cereals, which also act as a host, can make a significant difference,” he adds.

“As well as an increase in spring oats, we know growers are introducing grass crops into rotations to manage blackgrass. With ryegrass another susceptible host, this autumn’s outbreaks could also be an early warning for these growers in the East.”