Attack of the Flea Beetles

Flea Beetle on Rainbow Kale

Tiny hopping beetles in shades of metallic green or decorated with orange flame stripes, they would be cute. Would be, were it not for their evil streak.

I know that they are just doing what comes naturally to them (See the holes in that kale leaf. That is the nature of the flea beetle.) but I still choose to think ill of them.

As pesticide free farmers we are faced with an annual dilemma when it comes to the flea beetles. Flea beetles eat small holes in brassica plants, also known as crucifers or members of the cabbage family.

Because brassicas tend to do well in cool, short season climates like the Upper Peninsula, we grow about 15 different crops that flea beetles like to dine on.  As long as the plant being fed on is established the flea beetles don't really hurt it, they just cause cosmetic damage.

Like this:

Or this:

Seedlings are a different story. Hungry flea beetles can munch a radish seedling into oblivion if given the opportunity. 

So here is our dilemma. What do we do about this insatiable insect? 

We have a few tricks up our sleeves. Garlic oil sort of kind of helps a little. Row cover (see the photo below) helps even more by literally hiding the tasty brassicas from the beetles.  

Kale, Broccoli, Brussels Sprouts and Cauliflower in the foreground.
Two rows of mustard and radish seedlings hiding under row cover in the center.
Peas and Favas in the back.

So, we use row covers when we direct seed brassicas, to protect the seedlings. Sometimes we apply garlic oil to the row covers if the beetles find their way under. I'm not convinced that the garlic oil does anything but make us feel better though.

Our seedlings almost always survive with this treatment, but not unscathed. Our mustard and radish greens are always a bit holey.

And what about the kale, cauliflower, broccoli, and brussels? They are just left in the open to fend for themselves against the flea beetles.

We start those crops in the greenhouse, then transplant them into the field. By the time we plant them they are too big to hide under row cover, and they would have to come out sooner or later even if we could cover them at first.

There is a chemical option for treating the flea beetles. It's even allowed under many organic certification programs. Pyrethrin. It comes from flowers (Chrysanthemum cinerariaefolium) that look like oxeye daisies. It has been used for 100 years and is generally considered the safest insecticide to use on vegetables. Organic growers use it. It's probably okay, right?


Well...it is a neurotoxin to all insects, not just flea beetles. It is also toxic to fish. It can cause symptoms such as drooling, seizures, and death in humans (granted, only if consumed in large quantities - in small quantities it is completely non-toxic to mammals). 


Every year when the flea beetles attack we say to ourselves "We could use pyrethrin. It would work." And we decide not to.


We don't want to spray poisons on our food. We just don't. So the co-ops don't pay us as much for our arugula, our farmers market customers baulk at the holes in our kale, and we worry that the CSA members won't understand. That's the price we pay for our decision. We think it is the right one.