Flea beetles are a skittish pest and are able to create a lot of damage while - on the whole - managing to get away with with it scot-free. Why, well it's because of their size and speed, a flea beetle is not much more than 1mm in length but it can jump approximately 1ft in distance in a single bound. This being the case, as soon as you are close enough to see one, it would have already hopped off, disappearing into the undergrowth. Because of the flea beetle ability to disappear fast the culprit behind such damage is often miss-identified.
Cause: Even though these tiny, fast moving insects are difficult to spot, there are perhaps the most easily recognised pest of tomato plants due to the characteristic damage that these beetles cause.
Symptoms: These beetles can cause significant damage by leaving copious amounts of small holes in the leaves. As the leaves grow, the holes become larger and end up looking as though they have been hit by a shotgun blast. This infestation is usually experienced at two distinct times of the year, usually in April and July.
Control: Flea beetles are difficult to control as they have a habit of ‘hopping’ away if disturbed, making contact insecticides a bit 'hit and miss' in their application. However, you can also consider “trap crops” such as radish which may help lure the flea beetles away from your treasured tomatoes. So long as the radish is not in flower (as the applied insecticide will then harm beneficial pollinating insects) you may wish to use a systemic insecticide, however this will make the radish crop inedible. With this in mind, remember to label it clearly to prevent human ingestion.