How to control flea beetles in your garden

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By Jeneen Wiche

After the heat-wave in mid-May flea beetles seemed to have settled on just about everything I had growing in the garden. Bok choy, potatoes, tomatoes and turnips looked as if they were shot full of tiny holes! I pick and squish and drown but that doesn’t really work with the tiny flea beetle. As you know I do not use chemical pesticides in the vegetable garden. I will reach for a bio-insecticide if I must, however. Bio-insecticides include plant oils and compounds, naturally occurring bacteria, viruses and protozoa. We are essentially using nature to eat nature.
Bt, or Bacillus Thuringiensis, has been the stand-by for many years. Bt is a naturally occurring soil bacterium most effective on early stage caterpillars.  The pest must ingest the Bt which then disrupts the gut acting as an appetite suppressant so it stops eating resulting in death. Bt is great but it has no efficacy against beetles. My go-to in the bio-insecticide arsenal now is Spinosad. Spinosad proves to be more broad spectrum then Bt (with minimal impact on beneficial insects like bees, earth worms, lady bugs and hover flies because they don’t eat the foliage of the treated plant).
Spinosad is a naturally occurring soil bacterium and it has a rather funny story about its discovery. A soil scientist on vacation in the Caribbean took a soil sample from an abandoned rum factory floor and discovered a fermented soil bacterium (which has never been found anywhere else since.) Science recognized the bacterium as a new species so it needed a new name: Saccharopoly spora, now referred to as Spinosad. 
It is all about what you eat, right? So, when a pest eats the leaf of a treated plant (like all stages of the Colorado potato beetle do, for example) the bacterium is ingested, it then over stimulates the nervous system resulting in death. I treated the garden for my flea beetle problem and the next day there were very few pets remaining. I will need to watch the weather, however, because once the heat returns so will the pests! 
Here is the note of caution, though…don’t over-use a good thing!  History has taught us that pests are resilient. They are better survivors than we are I dare say and the strongest survive. Over-using any product means that those that do survive are the super bugs of the lot and the following generations will work hard to develop a resistance to a very effective bio-insecticide. Use as directed only when the pest pressure is apparent, it does not work to deter pests only to control those that are present. 
I have also used beneficial nematodes to control flea beetles in the vegetable garden with success. So, it seems that allowing the garden to reset its natural balance may be the answer after all. Give bio-insecticides a chance before reaching for synthetic chemicals that prove to be harder on the ecology of the garden then just the pest you are trying to control.