Vermeidung und Reduktion von Möhrenfliegenschäden im Ökolandbau

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.