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Orange Wheat blossom midge – May 2020

25 May 2020

Orange wheat blossom midge should appear soon in Scottish crops.

Midges need a warm, dry spell of weather after rain to emerge – we have just had the rain and it’s now warm and sunny so conditions are favouring the midge. The midges only lay eggs in the ears from early ear emergence (GS51) up to GS59 The best time to look for midges is on warm, still evenings by standing in the crop and looking for the midges resting or flying around the ears of the crop. Orange wheat blossom midges are around 3mm in size. For feed wheat crops, spotting 1 or more midges per 3 ears are needed to justify an insecticide, and for milling wheat crops, 1 or more midges per 6 ears are needed to trigger insecticide treatment.

Pheromone traps can also monitor the appearance and numbers of midges in crops, and these need to be checked regularly during the susceptible growth stage of the crop. Thresholds for pheromone trap catches recommend that sprays are only necessary when trap catches exceed 120 midges a trap a day. Monitor fields daily when trap catches exceed 30 midges a day.

Insecticide treatments need to be applied as soon as possible once the threshold levels outlined above are reached, as they target the midges to prevent egg laying rather than the eggs and larvae of the midge. Remember that the window where damage occurs is between GS51-59, so where the crop has yet to reach GS51 or is beyond GS59 then there is little chance of any midge larvae causing damage.

Several varieties have full resistance to orange wheat blossom midge so will not require any insecticide treatments (e.g. Skyfall, LG Detroit, KWS Firefly, KWS Barrel, KWS Basset, Elicit, Zulu, LG Skyscraper, LG Spotlight, KWS Jackal, Elation, LG Sundance, LG Motown, Leeds, Myriad, Viscount, RGT Gravity, Gleam, KWS Kerrin, KWS Crispin).

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