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Integrated control of wheat blossom midge - LK0924

Wheat blossom midge is a common pest of wheat causing severe yield losses in years of severe infestation (Oakley, 1994). The wheat blossom midge came to prominence in 1993 when it was found across large areas of the UK. This particular year demonstrated the vulnerability of the UK wheat crop to this damage. Significant yield losses were recorded in addition to severe quality degradation. In addition to the known risk of reduced Hagberg falling number (a consequence of conversion of wheat starch to sugars), recent work in Canada and the USA has confirmed that the midges both encourage and transmit Fusarium graminearum and encourage Septoria nodorum (Mongrain et al., 1997 & 2000; Wellso & Freed, 1982). These are particularly damaging diseases, known to have adverse effects on physical grain quality as well as encouraging the development of potentially injurious mycotoxins, which are of particular relevance to the food industries, who are also concerned over the level of insecticide use on crops. The 1993 outbreak showed significant differences in varietal susceptibility to the midge with some varieties showing significantly greater yield losses and quality degradation.
Though perceived by some to be a 'sporadic' pest, the midge is in fact present in all wheat crops in the UK and affects the quality of field crops in most years, and is known to cause regional problems in 'hot spots' of infection in the majority of years. As the larvae are hidden within the ear their presence is often overlooked and the actual degree of damage to UK crops is poorly appreciated. Incidence has increased across a wide geographical area since 1998. The damage caused by this pest is increasing across France, China and Japan as well as in North America and the UK, being favoured by current trends in climate change.
A forecasting system was developed after the 1993 outbreak utilising soil sampling to determine the level of pupation and give warning of flights of adult midges (Oakley et al., 1998). This system is operated for Dow AgroSciences Pest Watch and warnings are issued when a hatch of midges is imminent. The advice given to farmers when a hatch is anticipated is to inspect crops during the ear emergence growth stage on evenings suitable for midge activity. A number of problems, however, reduce the effectiveness of this advice:
1. Farmers have difficulty in deciding on the suitability of weather for midge flight, defined as air temperatures being above 14C with wind speeds below 11 km/hour when light levels fall below 1800 lx (Pivnick & Labbé, 1993). This occurs around 20:00 h on a bright day but cloud cover can encourage midges to fly earlier when temperatures would have fallen below the minimum threshold by 20:00. Winds often drop around dusk on days which otherwise seem unsuitable.
2. No more than 75 minutes is usually available between the start of flight and dark so that only a few fields can be observed on any one night. This makes for great difficulties for farmers and agronomists with many fields to cover over a wide area. The general practice is to select one or two indictor fields thought to be at greatest risk.
3. Under suitable conditions midges lay all of their eggs within three nights of hatching and few adult midges can be found during the day. Under adverse conditions the midge can survive for up to three weeks and large numbers may be found resting in crops, so that daytime observation of numbers can be a very misleading indicator of risk.
Because of problems of assessment the tendency has been for some farmers to adopt a prophylactic approach of applying a broad-spectrum organo-phosphate or pyrethroid insecticide with an ear emergence/start of flowering fungicide application. Around 250,000 ha have been treated in this way each year since 1994 according to the MAFF Pesticide Usage Surveys. However, depending on the timing of this application with the regard to the unknown pattern of midge activity, the efficacy of such a treatment is highly variable. Many farmers have either not applied an insecticide where required, or applied an ineffectively timed one, so that damage from the pest continues at a high level. The industry requires a better means of detecting risk in the field and a better understanding of the susceptibility of the varieties grown so as to be able to replace the inefficient prophylactic use of insecticides with a more rational approach.

Aim of the project
To develop an integrated control strategy for wheat blossom midge based on the use of more resistant varieties with a trapping system to determine the need for selective insecticide treatment.
a) To identify the potential of genetically derived resistance for the reduction of susceptibility of winter wheat to larval attack.
b) To improve field assessment of risk with pheromone and volatile chemical based traps for adult midges.
c) To develop an integrated approach to control of wheat blossom midge with less reliance on routine insecticide treatment.
Project Documents
• Abstract : LK0924 Wheat blossom midge Abstract   (8k)
Time-Scale and Cost
From: 2001

To: 2004

Cost: £196,357
Contractor / Funded Organisations
Advanta, John Innes Centre (BBSRC), Rothamsted Research (BBSRC), AgriSense BSC Ltd, Morley Research Centre, ADAS UK Ltd., Home Grown Cereals Authority, Dow Agrosciences Ltd, Nickerson UK Ltd, Elsoms Seeds Ltd
Arable Farming              
Climate and Weather              
Climate Change              
Crop Pests              
Insecticide use              
LINK Programme              
Natural Resource Use              
Sustainable Farming and Food              
Sustainable Production              
Wheat Production              
Fields of Study
Arable Crops