Today I managed to capture my enemy - but only on camera:
|Cabbage Root Fly|
I was on the lookout because last time I was weeding the brassicas (Radishes and Swedes) the seedlings looked like this:
My first suspicion was Flea Beetle so I made up the contraption below. It is a spare length of grease band taped to the underside of a cardboard sheet with flappy bits to brush across the top of the seedlings. This is based on the idea that flea beetles jump up when disturbed (?).
Sadly the result was non existent. Answer: it's not primarily flea beetle. Having seen flies on my last visit I took my camera along (as well as my Weapon of Minimal Destruction) to help identify the culprit. Massively blown up it is the first picture. Cabbage Root Fly (CRF). It seems there are at least three generations of CRF each year and these are the parents who lay their eggs in the ground near brassicas. The emerging grubs then tunnel into the stems and roots of brassicas. That's why brassicas collars were invented: to stop access to the stem at soil level. I'm not sure which manifestation of the CRF is eating the seedling leaves but I do know there are plenty of these small housefly-like flies active around the seedlings. They are clearly too clever to fall for my flea beetle trap. I did manage to squish a few at ground level with my fingers. Now that's what I call organic gardening!
For good measure I've added my best shot of a flea beetle taken on the same day. These are smaller than the CRF so harder to capture. The give away for identification is the lines on the abdomen (and they are black).