Someone asked me the other day, “do you spray your garden?” and “what sprays do you use?” I gave her a short list of materials that I found useful in my garden. Most people agree that these materials are OK for organic gardeners.
I have been a fan of Bt (Bacillus thuringiensis) since I started gardening in the 1970’s. It is an insecticide made of naturally occurring bacteria found in garden soil. Only surface feeding caterpillars like cabbageworms are killed by it. Bt must be eaten by the caterpillars in order to work. It does not harm beneficial insects.
Spinosad is another insecticide derived from soil bacteria. The bacterium was discovered in the soil at an abandoned rum distillery, so the story goes. This insecticide kills a wide range of insects. It too must be eaten in order to be effective. This reduces the likelihood that the Spinosad would kill a beneficial insect.
Pyola is a mixture of canola oil and pyrethrins. This effective insecticide has the potential to kill any insect good or bad so be on the lookout for honeybees or other helpful insects before you spray.
For disease control, I use a liquid copper fungicide. The other material I’ve used with mixed results is potassium bicarbonate. Potassium bicarbonate is chemically similar to sodium bicarbonate or baking soda.
You can make your own homemade garden fungicide by mixing one tablespoon of baking soda and one tablespoon of liquid dish soap together in one gallon of water. Just make sure your plants have had plenty of water to drink before you spray this mixture.