Vermeidung und Reduktion von Möhrenfliegenschäden im Ökolandbau

Summary

The carrot fly Psila rosae is a major pest in organic carrots. Damage strongly depends
on local factors and is often found when cropping intensity is high. However, limited
field site availability may require growing carrots close to crop sites of preceding
years. Here, results of the first two years show carrots may be protected from
infestation using trap crops (also carrots) to bind and actively reduce the local P. rosae
population. To protect the main carrot field, pair wise arrangements of carrot strips
were sown 1) directly at the previous year carrot field and 2) close to the main field to
protect the present carrots. During the first generation a mean sum of 36 and 62 flies/
trap in 2007 and 2008 respectively were monitored with yellow sticky traps (Rebell
orange®) leading to high infestation pressure. Monitoring results show the flies are
effectively attracted and bound by strip 1) but still negotiate distances of 130 and 180
metres between previous and present carrot fields. Carrot strip 1) was to be removed
in time to prevent the second generation of P. rosae to develop. Based on the
simulation model SWAT monitoring data and damage assessment was used for timing
concerns. Hence, critical issues about removing the trap crops are discussed. In 2008
eclector traps were established onto the sites of removed trap crops to further verify
the effectiveness of trap crop handling. First results positively support applied
techniques. All trials are to be repeated during field season 2009.