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Witches’ Brews And Old Wives’ Tales: Insecticidal Soap

Article by Kaydie McCormick, Residential Horticulture Agent & Master Gardener Volunteer Coordinator

A large part of an Extension Agent’s job is helping residents, businesses, and farms to determine what the most scientifically and economically sound course of action is. What this means in my job, is I get to spend a little bit of my time every day researching the newest information from the Universities around the country. I then translate those horticultural practices into something useful for the homeowners in Seminole County.

One of my favorite classes where all this information comes together is Witches’ Brews & Old Wives’ Tales, a class I typically teach to our residents sometime in the fall. Below you’ll find one of the topics I cover during the class.

Witches’ Brew: Insecticidal Soap 

At home versus store bought

I have a lot of homeowners tell me they are looking for an organic alternative to the chemicals sold in the store… an organic alternative like the dish soap they use to scrub their pots and pans. Unfortunately, most of the soap formulations found today are not the same as the ones found when the recipes for at home soap sprays were made.

These ‘witches’ brews’ are more dangerous for our plants because of the addition of detergents in dish, hand, and body soaps, along with reformulations that include more sodium. They can strip away the vital wax layers that keep the leaves from drying out, or burn the plants through other means.

Store bought insecticidal soaps are often labeled for organic use.  They should be safe to use in your garden as long as you follow the label. These insecticidal soaps work the same way that the old homemade soap sprays do, but without the added risk of the scents, detergents, and additives that are often found in them. You can read even more about the topic on the UF/IFAS website [here].

When to Use Insecticidal Soap

Insecticidal soap controls small, soft bodied insects like aphids, whitefly, mealybug, and scale. It kills only what it comes into contact with when wet. This means time of day can be important when spraying (early or late to avoid most pollinators).  Typically insecticidal soap sprays will be used every 5-7 days for 2-3 weeks to reach adequate control of a pest. Make sure you follow label directions. Many pesticides can cause damage to plants here in Florida if the temperature is too hot. The label will tell you the best conditions to spray in.

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