Detection preventing devastation

Detection is a key factor in preventing the devastating rampages through wheat crops of the larvae of the tiny insect, orange wheat blossom midge (OWBM). OWBM was difficult for farmers to spot before the development of a sex pheromone trap that lures male insects to a sticky end before they mate and provides a real-time gauge of the likely level of infestation.

The alert affords an opportunity to spray insecticide before significant damage is done and gives farmers the confidence not to spray when the pest is not present. In four out of five years, the larvae emerge too early or too late to hit the wheat when the crop is at its susceptible growth stage, a narrow window of less than one week.

Combined with OWBM resistance, which has now been bred into at least 40% of UK wheat varieties, and an information system to support decision making on farms, Rothamsted Research has helped to solve the worst effects of the midge.

Crop losses to this pest are substantial

When unmanaged, damage can be significant. In an outbreak in the UK in 2004, crop losses amounted to around one million tonnes, about 6% of production, and were compounded by reductions in grain quality despite insecticide application to around 500,000 hectares. In 2007, in China, OWBM affected more than 200 million hectares of wheat.

In March 2016, the UK government banned the use of the most effective insecticide, Chlorpyrifos. As a result, the availability of resistant wheat varieties is a major benefit for the UK arable industry. Although originally discovered in lower quality wheat, the resistance has now been bred into the highest quality varieties. Farmers can choose a variety from a recommended list held by the Agriculture and Horticulture Development Board, which is funded by UK farmers and growers. The AHDB also supplies factsheets to explain research findings and advise on best practice for pest management.

Overuse could help the midge develop tolerance

A word of warning comes from the Canadian Prairies, however. Farmers there have relied on a midge-tolerant wheat since 2010, but there is concern that OWBM will overcome the tolerance and start to devastate crops again as it did in the early 1990s. As a result, since 2015, farmers have been strongly encouraged to limit the way they use the resistant variety so as to prolong its effectiveness. So far, there are no such restrictions in the UK.

For more information:
Contact: Gia Aradottir

Read: Bruce, T.J. et al., 2007, Pest Manag Sci 63:4956

Date: May 2017

Lilian and John Wangombe