Saddle gall midge (Haplodiplosis marginata/equestris) is a pest of cereal crops across Europe. It was first recorded in the United Kingdom in 1889 and has since become a sporadic pest of wheat, barley and rye crops, particularly in central and eastern areas of the country. Between 1967 and 1972, severe outbreaks of the pest were reported in isolated areas of the UK causing significant crop damage. Since this time saddle gall midge has not been considered to be an economically important pest. However, in 2010 localised outbreaks were reported in central England and have continued to be reported in subsequent years. In the most severe of these cases yield losses have been as high as 70%. There remains much to be understood about the causes of such outbreaks and how they can be predicted and mitigated; and as such, current control methods are limited. Much of the existing research on this pest has been done in central and northern Europe where it has historically been more prevalent. In the United Kingdom, saddle gall midge has been comparatively understudied in relation to more common crop pests.
This project will assess factors affecting soil populations of saddle gall midge with a view to predicting and mitigating outbreaks of this pest. Adult midges lay their eggs on cereal and grass leaves around May or June. Following hatching, the larvae migrate down the leaf and feed on the stem from within the leaf sheath. Larval feeding on the stem results in galls which appear as the 'saddle shaped' depressions that are characteristic of this species. Gall formation can cause significant damage to the crop by restricting the flow of nutrients to the ear. The galls can also weaken the stem which increases the risk of lodging. The damage caused by the larvae can also leave the plant vulnerable to secondary attack by bacteria or fungi, particularly in wet conditions.
On reaching maturity, the larvae drop from the stem and enter diapause in the soil where they overwinter. Owing to the relatively short flight of adult midges, potential crop damage is closely linked to the size of the larval population in the soil. Soil populations have been shown to be a potentially useful predictor of adult emergence as development stages can be monitored effectively. However, with so little known about the factors affecting soil populations, there is currently no useful predictive emergence model.
This project aims to address that gap in knowledge on saddle gall midge in the UK through a combination of field, semi-field and laboratory studies. The effect of environmental conditions, natural enemies and cultural control on soil populations of this pest will be assessed. This information will contribute towards a model for predicting adult emergence and severity of attack, and towards developing effective measures of control. In the future it is hoped that this knowledge will be used to the mitigate risk and severity of outbreaks of saddle gall midge in cereal crops in the UK and on the continent.