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After the heat-wave in late May the blueberries ripened like wildfire, the Colorado potato beetle larva peppered the Pontiac potato patch and the cabbage worms nearly devoured my kale. I pick and squish and drown but so much was happening at once I needed a little assistance. 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. We now have something new to the bio-insecticide arsenal which proves to be more broad spectrum (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) and it is called Spinosad.
Spinosad is also also 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 injested where it over stimulates the nervous system resulting in death.
Don’t over use a good thing
I treated that row of Pontiac potatoes that had tiny to big larva as well as beetles and by the following day all pests where either dead or nearly there. 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 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. And, to follow up on my column from a couple of weeks ago about using beneficial nematodes to control flea beetles in the vegetable garden: it looks to be a success. The new growth on peppers, tomatoes and arugula is all hole-free. So it seems that allowing the garden to reset its natural balance may be the answer after all. Let’s see how long the peace will last.
(Jeneen Wiche is an avid gardener from Shelbyville. She can be reached at Jwiche@shelbybb.net.)