Integrated control of wheat blossom midge - HGCA

4. CONCLUSIONS• The project has made considerable progress towards the development of a monitoring system formale S. mosellana and identified the optimum pheromone release rate and methodology for use inpheromone traps in the UK.• The pheromone, 2,7-nonanediyl dibutyrate, (Gries et al., 2000) performed well for indicating theonset of S. mosellana flight activity in the vicinity of wheat fields.• It appears that there is a relationship between numbers of midges caught in the traps and thelikelihood of crop damage even though the pheromone traps catch male rather than female insects.• The threshold level at which an insecticide application to protect the crop is warranted is probablyaround the level of 20 midges per trap per day but further work on threshold levels for pheromonetraps i.e. the numbers of insects that indicate economically damaging levels is necessary.• It is likely that the threshold will vary according to the level of susceptibility of the wheat cultivarbeing grown and the market for which it is intended. There would be a lower threshold for breadmakingwheat than feed wheat.• There are possibly situations in which immigration of female S. mosellana would mean thatpheromone traps underestimate the threat to the crop and this aspect requires future investigation.• Wheat volatiles attractive to female S. mosellana were identified as acetophenone, (Z)-3-hexenylacetate, 3-carene, 2-tridecanone, 2-ethyl-1-hexanol and 1-octen-3-ol from wheat cultivar ‘Lynx’ andα-pinene, 6-methyl-5-hepten-2-one, and 2-dodecanone from wheat cultivar ECO22. 3-Carene andacetophenone were identified as active components of both varieties.• These showed a level of attraction similar to the pheromone in laboratory olfactometers.• Ratio of plant volatiles was crucial because use of an incorrect ratio made the mixture unattractive.• Development of a field stable formulation of plant volatiles maintaining ratio integrity throughoutthe season has proved difficult.64