The geographical distribution and phenology of WBF are matched more closely with those of couch than with those of other hosts. These factors suggest that couch, and not wheat, is the preferred host. Aspects of this hypothesis were tested in the laboratory, glasshouse and field. In choice test bioassays neonate larvae preferred couch seedlings and their exudates to wheat seedlings and their exudates, and couch rhizome exudates to controls. Couch seedling exudates had attractant properties, whereas wheat exudates had attractant and arrestant properties, when compared with controls. The larvae were photophobic and positively geotactic. In a pot trial, symptoms of infestation appeared earlier in couch than in wheat. At first, larvae encouraged production of extra shoots, especially of couch, which they kill. After 5 weeks, infested plants suffered a relative reduction in number of shoots, but uninfested neighbouring plants, especially wheat, compensated for this by producing more shoots themselves. Larvae raised on couch emerged as adults earlier than those raised on wheat. They thus develop more rapidly, and use more resources, on couch than on wheat, i.e. they are better adapted to couch as a food source. Earlier eclosion in the field would allow adults to make better use of favourable weather conditions, and to live longer, mate more often, and produce more eggs. In the laboratory and the field adult WBF preferred to rest on couch than on wheat. They also preferred taller plants and those nearer the edge of a stand. Buried couch rhizomes did not encourage oviposition by gravid WBF females, either in the laboratory or the field. These findings support the hypothesis that couch is the preferred host of WBF, provide a partial explanation of high larval mortalities on wheat, and suggest that attractants isolated from couch and arrestants isolated from wheat could be used to control WBF larvae if incorporated into buried granules.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:657333 |
| Date | January 2001 |
| Creators | Marriott, Charles |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/28541 |
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