Chemical control of Haplodiplosis marginata (Diptera: Cecidomyiidae)

The saddle gall midge, Haplodiplosis marginata (von Roser), is a European pest of cereals. The larvae overwinter into the soil. Emergence of adult midges occurred during the spring and after mating, females lay their eggs on the leaves of cereals and several grasses. Eggs hatch a few days later; young larvae crawl to the stem and introduce themselves between the leaf sheath and the stem, were the larvae develop. As reaction of the presence of midge larvae, stem produce a longitudinal depression of 6-7 mm ended by two ridges looking as a horse saddle. When galls are numerous, they can cause break of stems and important yield losses.
The saddle gall midge, which is a major pest in Central Europe, is not very well known in the Western part of the continent. It had already caused huge damage during outbreak periods. The last one reported in Belgium and in The Netherlands occurred between 1965 and 1970. Later, it was never reported again until 2010, where large populations and severe damage were observed, especially in the Flemish polders, a region with clay soils where wheat is cropped intensively.
Faced with the resurgence of this pest, we sought to develop effective curative control. To date, crops chemical protection seems to be the only solution in case of heavy emergences.
Experimentation was conducted in a highly infested field (Meetkerke, Belgian Polders), according to a randomized complete block arrangement with four replications.
Foremost, a lambdacyhalothrin-based insecticide was used to evaluate efficiency of several protection schemes, ranging between one and four spray(s). The large spread of flights observed during the 2011 spring allowed to highlight the effect of treatment date on the attack intensity and also on the galls distribution along the stem, on the different internodes.
Moreover, several insecticides already registrated in cereals against aphids were compared for their efficacy against saddle gall midge. Studied pyrethroids have shown a very good efficacy, ranging between 75 % and 87 %, when applied twice with a 2 weeks interval.
To be efficient, chemical spray must be synchronized with the flights and egg laying periods. Monitoring the phenology of flights is thus essential as part of integrated pest management against saddle gall midge.