CONSERVATION EXPERTS have warned farmers to check thresholds thoroughly before spraying for orange wheat blossom midge.

Chlorpyrifos, currently the only product approved for use in the UK, is toxic to most insects, pointed out the Game Conservancy Trust.

Using it will reduce the availability of important chickfood for many farmland birds, said the trust.

GCT head of entomology John Holland advised growers to check each field to see if a spray is really necessary since the distribution of the midge can be quite patchy.

“Midge can quite often be higher in the headlands, but this is also the area where partridges forage for insects.”

Dr Holland said the ADAS threshold of one midge per three ears for feed wheat and one per six ears for milling and seed wheat are conservative.

Growers should consider the toxicity of the recommended insecticides, which can cause long-lasting damage to insect populations, he added.

But ADAS entomologist the unpredictability and variability of OWBM meant that some damage to beneficial insects was inevitable this year.

“The problem is many fields are looking so bad growers will have to spray, so you can‘t avoid hitting natural predators.”

UAP technical director Chris Bean said farmers must treat the problem on a field-specific basis and get the timing absolutely right.

Midge larvae will only develop if laid in the ear within 7 days of ear emergence so it is only useful to spray during the first five days of ear emergence.

“A lot of crops are starting to flower now, so are coming out of the main risk period,” said Mr Bean.

“The trouble is that there may be secondary tillers coming on, which, if infested, could hit yield and quality.”

Variety choice also has a bearing, he added, with Robigus appearing to be a variety with “some immunity” to wheat blossom midge.