Bt and Spinosad: organic pest controls for your garden
Bt and Spinosad: two organic insecticides to try in your garden this season. Here's a rundown.
Eco-conscious gardeners often are faced with some difficult decisions when it comes to pest control in organic gardens. Effective pest control often comes with the unwanted side effect of harming beneficial pollinators and even leaving residue on food, which defeats the purpose of why many people choose to grow their own food in the first place. In recent years, home gardeners have had more types of organic and safe pesticides to choose from.
Here’s an overview of Bt and Spinosad, two organic pesticides to make a part of your garden this year. Bt and Spinosad are derived from bacteria, making them biopesticides. Biopesticides are usually much safer than artificial pesticides because they’re derived from natural proteins and compounds, so they’re not as volatile. They’ve been studied extensively for their efficiency in getting rid of harmful pests while also being proven safe for pollinators, pets, and people.
Bt (Bacillus thuringiensis)
Bt is a type of soil bacteria found in many parts of the world. There are many different varieties of Bt, and each one is effective at controlling different species of pests. When ingested, the spores destroy the pests’ digestive systems and are effective only for that species. That’s why, when choosing a Bt pesticide, you should know which pests you’re trying to get rid of so you can choose the appropriate strain of Bt. Bt pesticides are commonly sold as sprays, which distribute the spores onto the surfaces the pests will eat.
Bacillus thuringiensis var. israelensis (BTi) and Bacillus thuringiensis var. kurstaki (BTk) are the most common forms of BT control methods available. BTi targets blackflies, mosquitoes, and fungus gnats. BTk targets many types of caterpillars, including gypsy moth caterpillars, hornworms, cabbage worms, cutworms, and more. It will also harm the caterpillar stage of many species of butterflies, so if you have a butterfly garden, BTk should be applied after the butterflies have matured. Another factor to keep in mind is that BTk does not affect eggs or mature pests, just the larval stages.
Even with these caveats, BTk is much safer than commercial chemical pesticides since it doesn’t have any effect on humans or pets, and won’t pollute water or soil since it’s just spores. Exposure to sunlight will gradually degrade Bt, but since it’s not harmful unless ingested, it won’t burn or harm leaves and you can apply as much as needed.
Thuricide Liquid Ready-To-Use - 1 gal - Essex County Co-Op (essexcountycoop.com)
Thuricide Liquid Ready-To-Use - 32 oz - Essex County Co-Op (essexcountycoop.com)
Thuricide Liquid Concentrate - 16 oz (essexcountycoop.com)
Summit Mosquito Dunks Repellent Solid For Mosquitoes 3.7 OZ - 6 pk (essexcountycoop.com)
Spinosad (Saccharopolyspora spinosa)
Spinosad is an organic pesticide relatively new to the market. It’s derived from a byproduct of Saccharopolyspora spinosa, a type of bacteria found in the soil just like Bt. The active ingredients are two chemicals, spinosyn A and spinosyn D. They act as a neurotoxin for many insects, causing muscle spasms and death. It is effective against thrips, caterpillars, bagworms, and beetles. Spinosad comes in powder or liquid spray form, but is applied the same way. It doesn’t accumulate in soil or water so you can maximize their effects without worrying about contaminating the environment.
The main thing to consider when using spinosad in your garden is that it is also toxic to bees. For many gardeners this is a dealbreaker, but spinosad’s effectiveness makes it an ideal pesticide for many. To protect bees from the effects of spinosad, consider the timing of your application. If using a liquid spray, apply at dusk or the very early morning before the bees become active. Once the spinosad dries, bees will no longer be affected. The Co-Op carries these spinosad products:
Captain Jack's Deadbug Brew Ready-To-Spray - 32 oz - Essex County Co-Op (essexcountycoop.com)
Captain Jack's Dead Bug Brew Dust - 4 lb (essexcountycoop.com)