UF/IFAS Okeechobee County Extension Service

458 Highway 98 North

Okeechobee, FL 34972-2578

Phone: (863) 763-6469

E- mail:  dfculbert@ifas.ufl.edu

May 14, 2003

Feature Article - for release the week of May 18, 2003

Dan Culbert - Extension Horticulture Agent

Safer Insecticides for your Florida Yard

Have you seen any bugs in your yard lately? Often callers to our office want to know what kind of chemical insecticide is recommended to kill a particular pest. Once we find out that the problem is insect related, often our office might suggest a kinder, gentler way to manage yard pests: soaps, oils, and "Bt" insecticides.

According to Georgia’s Grady County Agent Keith Mickler, horticultural oils and soaps were used more than 50 years ago in fruit trees and landscape shrubs. These worked well when properly applied, but were largely replaced with the use of synthetic chemical insecticides.

Today, the oils, soaps, and Bt's (Bacillus thuringiensis insecticides) have made a comeback. This is because they are relatively nontoxic to the user, are relatively safe to the good bugs in the yard and garden, and will control many stages of soft-bodied pests. Aphids, thrips, whiteflies, mites, and scales are all targets of oils and soaps.

Horticultural oil is especially formulated for use on plants. It is a petroleum-based oil with an emulsifier added that allows it to be mixed with water. When sprayed on infested plants, it plugs up the insects' breathing pores to kill scales, mites, and other insects by suffocation. Since this is a physical control, rather than by poisoning them, there is little danger that the pests will develop resistance.

Horticultural oils are usually classified as dormant oils, summer oils, or superior oils. Dormant oils are applied in the fall and winter before plants begin spring growth. Do not use dormant oils during the growing season unless the label specifically states that such use is safe.

Summer oils are lighter than dormant oils and are formulated for use during spring and summer. Superior oils are excellent products for horticultural pest control in any season. These superior oil products allow greater flexibility in their use and have been tested at temperatures in the mid 90's with no damage to shrubs

While there are thousands of soaps, only a few are effective as insecticides. Insecticidal soaps available today are made from potassium salt of oleic acid which is found in olive and other vegetable oils. Insecticidal soap physically disrupts the insect's outer protective cuticle layer and causes the insect to dry out. And that is just what these sap-suckers deserve!

Horticultural oil and soap products are available at local garden supply centers and nurseries. The oldest and best known oil is Volck oil. Horticultural oils are sold under various descriptive names such as "dormant oil," "oil emulsion," "safety-side," "summer oil," and "superfine oil." There are several soaps available for purchase, such as Safer’s Insecticidal Soap and M-Pede.

Thorough spray coverage is essential when using oils and soaps. These products are not poisons and must touch the pest, so all plant surfaces must be coated with spray. These products will need reapplication after a heavy rain, and will need to be re-applied as the plants grow larger.

Another Florida friendly product for controlling caterpillars is Bt, which stands for Bacillus thuringiensis - that’s why we call it Bt! It’s been used since 1972, and is now being genetically added to certain crops. It acts like a stomach poison against caterpillars - the larvae of moths and butterflies. Bt is best used when the caterpillars are small and they must swallow the Bt for it to be effective. After ingesting Bt, the caterpillar stops feeding within an hour and will die within several hours to days. Before dying, the caterpillar will become sluggish, discolor, then shrivel, blacken, and die.

Bt can be found under several brand names such as Dipel, Thuricide, and Sok-Bt, Stewart, Foil Javelin and Safer’s Caterpillar Killer. Some of these brand names are labeled only for use on certain kinds of places, so it’s important to read the label. And if you have a butterfly garden, keep Bts out of your caterpillar nursery. There are other forms of Bt which are used as mosquito larvicide, and others are used against certain kinds of beetles.

Though horticultural oils, soaps, and Bt.'s are less toxic than many insecticides, it is important to use them with caution. Soaps and oils can cause eye irritation. So, as with all pesticides, Read and follow the label carefully.

If you need additional information on least toxic insecticides, call or stop by our office at 458 Hwy 98 North. Our phone number is 763-6469, and you can email us at okeechobee@ifas.ufl.edu.

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Trade names, where used, are given for the purpose of providing specific information. They do not constitute an endorsement or guarantee of products named, nor does it imply criticism of products not named. The Florida Cooperative Extension Service - Institute of Food and Agricultural Sciences is an equal opportunity/affirmative action employer authorized to provide research, educational information, and other services to individuals and institutions that function without regard to race, color, sex, age, handicap, or national origin.  Florida Cooperative Extension Service / IFAS / University of Florida.  Larry A.  Arrington, Dean Last update: 06/20/2006 .  This page is maintained by Dan Culbert