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Savings of £15/ha

Growing a resistant variety such as Torch or Warrior will result in peace of mind, a saving of at least £15/ha on insecticide costs plus the additional costs of pheromone traps and no adverse impact on the environment or non-target pests as no insecticide need be applied.

According to Ed Flatman, resistance to orange wheat blossom midge (OWBM) could have a significant benefit for growers this year. "Agronomists are reporting high populations of aphids and pollen beetle, due to the mild winter and spring. Providing there is sufficient moisture, we may well be in for a bumper year for wheat blossom midge too. Growers of wheat varieties such as Torch and Warrior, both increasingly popular Group 3 varieties, won't have to concern themselves with setting out pheromone traps, monitoring insect populations and then deciding whether and when to apply the often broad-spectrum insecticides. Torch, Warrior and a number of other wheat varieties including our candidate variety Cougar have complete resistance to this pest and so do not require any control measures."

Ed explains that there is one major resistant gene, certainly only 1 chromosomal region. "It is hoped that this gene will continue to give durable resistance, as has been the case in widespread exposure to midges in Canada over a long period of time. The gene was already in some UK types by chance and by selective crossing has become more widespread. Most of RAGT wheats under development have this gene and we have an independent set of markers to track its now. The proposition of resistance to other insect pests is also being investigated."

Entomologist Dr. Steve Ellis of ADAS considers orange wheat blossom midge resistance in wheat to be very effective. "It is a sensible way to get round the problem much more easily and cheaply, particularly when you consider all the intricacies of setting out traps, assessing the need to spray and then assessing if the weather conditions and crop stages are right for an infestation to occur."

Getting spray timing right can be difficult

"Despite the widespread use of pheromone traps, it is still difficult to get the spray timing right. The traps, which should be put out into the fields a week before the first ears emerge, attract the male orange wheat blossom midge adults and it is the females that we want to prevent from laying their eggs. Damage to wheat varieties without in-bred resistance occurs if egg laying happens when the crop is at the vulnerable mid-flowering stage. The females will lay their eggs on resistant wheat varieties, but they are prevented from completing their life cycle through the variety's resistance mechanism," explains Steve.

Although we are not entirely certain, we think that the resistance gene confers wound plugs to be formed on attacked grain and so prevents larvae from feeding. The resistance is 100%, offering complete avoidance of pest damage, adds researcher Dr. Toby Bruce of Rothamsted Research.

Resistance to OWBM was first introduced in Group 4 and Group 3 varieties and is a desirable varietal characteristic across all Groups. There is no field evidence of any change or breakdown in the resistance to date, although it is only applicable to orange wheat blossom midge, far and away the more widespread species, and not to the lesser known yellow wheat blossom midge, says Dr Bruce.