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Plantwise Technical Factsheet

fly, wheat bulb (Delia coarctata)

Host plants / species affected
Agropyron (wheatgrass)
Elymus (wildrye)
Elymus repens (quackgrass)
Hordeum vulgare (barley)
Secale cereale (rye)
Triticum aestivum (wheat)
List of symptoms/signs
Growing point  -  internal feeding; boring
Stems  -  dead heart
Stems  -  internal feeding
Symptoms
Dead heart caused by the larvae boring into seedlings. Larvae develop in the central shoot, kill the growing point and then move to another plant (Ferrar, 1987; Smith, 1989; Griffiths, 1992).
Prevention and control

Cultural Control

Hill (1987) noted that in theory crop rotation should control D. coarctata by avoiding sowing winter wheat after fallow or root crops (including legume crops). However, this is not always practical as winter wheat is often the most suitable crop to sow after early-harvested crops. Young and Talbot (1996) found that fallow soils cultivated to produce a smooth tilth before the July-August oviposition period had fewer eggs laid in them than rough ploughed soils. Similarly, Kaack et al. (1989) found females had a strong preference for laying eggs in crops with a high leaf area index or coarse clodded fallow.

Scott and Greenway (1984) found that activated charcoal interfered with host seeking by young larvae, noting that charcoal in the soil above the level of the seeds reduced attack, although this does not appear to have been applied as part of a control strategy.

Chemical Control

Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources:


Impact
D. coarctata is probably the most serious pest of winter wheat in many areas of Europe, for example, Gair (1985) noted its prime importance in the UK. However, it is not usually a problem for spring cereals (Hill, 1987). The introduction of rotational set-aside in the UK has created ideal oviposition sites, and this threat is likely to strengthen the need to investigate alternative control measures (Young and Ellis, 1996).

Liu et al. (1987) reported losses of up to 50% in Ningxia, China, during 1982-86.

Crop damage has not been reported in North America, although the fly appears to be spreading as the geographic range of couch grass (Elymus repens) expands (Griffiths, 1992).
Related treatment support
 
External factsheets
Bayer CropScience Crop Compendium, Bayer CropScience, English language
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