Dennis Van Dyk, OMAFRA, Guelph; Manju Chandran and Mary Ruth McDonald, University of Guelph, Muck Crops Research Station.
For the first time in Ontario, feeding damage caused by flea beetle larvae has been confirmed in a commercial carrot field. The damage is characterized by irregularly shaped cavities along the length of the taproot (Figure 1). A trail of smaller feeding sites can sometimes be seen travelling down the length of the carrot (Figure 2).
Flea beetle was recently identified in California in 2012 as the cause of damage found in a number of carrot fields and has since become a more widespread issue. Prior to 2012 it is hypothesized that feeding damage was being misdiagnosed as cavity spot lesions caused by Pythium spp. which causes very similar damage (Figure 3). Accurate diagnosis is essential because management of flea beetle or cavity spot is very different.
Like other root vegetables such as potatoes, flea beetle larvae tunneling and feeding damage render the carrot unmarketable. Flea beetle adults do feed on the above-ground carrot foliage but are not considered an economic pest.
As this is a new pest to carrots there are no registered products for control in Ontario at this time. We will be monitoring carrot harvest this fall to determine the extent of damage. If you think you may have an issue with flea beetle, please contact Dennis Van Dyk at (519) 826-4587