Garden & Greenhouse October 2017 Issue - Page 50

FEATURESTORY by Nick Fraser Soap, Oil and Other Homemade Insecticides and Fungicides B ecause they are often primary components of many home remedies, it helps to have a good understanding of the use of soaps and oils for treating plant pest problems before looking into various other homemade potions. Soap Sprays There are three types of soap that gardeners through the ages have used to treat a number of plant insect problems. All soaps are fatty acid-based products, and to varying degrees, are one of the saf- est sprays to use in the garden. They primarily kill soft-bodied insects, such as aphids, mealybugs, spider mites, thrips, whitefl ies and immature leafhoppers. Repeated applications at one week intervals are gener- ally necessary to control high pest populations. I remember my grandmother washing dishes in a large pail in the sink and then dumping the soapy water over various plants in the garden. The belief Calcium Rich Mineral Composite ® Contains Calcium Sourced From Ancient Sea Beds element ™ The High Level of Natural Calcium: Supports Enzymatic, Cell Membrane, and GenERAL PLANT FUNCTIONS FOR ORGANIC USE 1-855-KELZYME Also Available in Granular form 50 was that the soapy water acted both as an insecticide and soil nutrient. Many gardeners have been add- ing small quantities of dish detergent with water and spraying plants with good results for years. There are other gardeners who prefer to use either natural liquid soap, available at health food stores, instead of dish detergent, and there are some valid reasons. Most dishwashing detergents have anti -bacterial properties that may have some harmful ef- fects on plants, particularly if the sprays are mixed too strong. The third option is to spend the extra money and purchase an insecticidal soap specifi cally formulated for use on plants. Commercially formulated insecti- cidal soaps are better than home remedies because they have been tested to be safe on a variety of plants. Perhaps the biggest mistake gardeners make in using soap sprays is not in the soap they select, but in mixing the spray too strong. Commercial insecti- cidal soaps will come with mixing instructions, and it is best to start half strength until you can determine how various plants react to spraying. A conservative mixture for soap spray is 1 to 2 teaspoons liquid soap added to 1 quart of water. A few drops of cooking oil can be added to help the mixture cling to leaves bet- ter. Guidelines for Insecticidal Soap Insecticidal soap is a contact material, meaning that insects must come into direct contact with spray for it to be effective. There is no residual benefi t of October 2017