Biologische beheersing wortelvlieg (Psila rosae) in 2009

Since 2007 Applied Plant Research (PPO) investigates whether the carrot root fly (Psila rosae) can be disorientated by applying strong smelling oils. A mature carrot root fly can find a carrot field by smell. The question is whether the smell of carrots may be masked by strong smelling oils so that the carrot root fly can not find the carrot plants. In 2008 we found an indication that strong smelling oil can reduce onion root fly damage. In the untreated plot 7% of the roots were affected by the carrot root fly and in the treated plot (masked by strong smelling oil) 1% of the roots were affected. In 2009 on 6 carrot fields and one root parsley field demonstrations were created by Dutch organic farmers to reduce carrot fly damage. In all the 6 carrot fields the root fly damage was too little to determine differences. The maximum percentage of infected carrot roots was below 3%. As a result, the effect of oregano-oil could not be determined. In the parsley root field damage was sufficiently high to see effects of the oil treatment. In the patch protected by onion oil 1.5% of the roots were affected. At a distance of 150 m from this patch no infected roods were found. At a distance of 270 m from the patch 11.5% of the roots were affected. The oils used have a natural origin (extracted from plants). The method is selective because only insects reacting on the carrot smell are affected. They have more difficulty in finding carrot fields, or can not find them at all. If this method functions well, it can be used in organic and conventional cultivation of carrots.