Recipe for an Organic Garden Spray for Bean Beetles

Neem Oil Spray

• According to Rodale's "Ultimate Encyclopedia of Organic Gardening," neem oil helps control adult Mexican bean beetles. Neem oil comes from the Australian neem tree (Azadirachta indica) and has been shown to repel and kill a broad range of insects while having minimal impact on beneficial insects. Although you'll find ready-to-spray neem oil products at your garden center, making your own is more cost effective. Blend 2 tablespoons of pure neem oil, organic if you prefer, with 1 quart of water, then add the liquid to a spray bottle. An optional drop or two of liquid soap helps the neem oil stick to plant leaves longer. Neem will kill other insects that feed on the plant too, so avoid spraying flowers visited by bees and other beneficials.

Basic Soap Spray

• Soapy sprays work well on pests because the fatty acids in these soasp paralyze them, making them unable to feed. For bean beetles, especially those at the larvae stage, use insecticidal soap spray. A homemade version is made by blending 3/4 teaspoon organic nondetergent liquid soap, such as castile soap, with 1 quart water, shaking well and pouring into a clean spray bottle. Because the formula works best with soft water, filtered water or spring water is best if your household water supply has a high mineral content. Castile soap is sold at natural food stores, health stores and larger department stores.

Spray Additions

• Some common ingredients have additional repellent properties and may be added to either neem or soap spray formulas. Garlic is a commonly-used ingredient in repellent, and organic garlic is sold in many supermarkets. Chop about 6 cloves finely and blend them with 1 quart of plain water. The strained liquid can be used in place of some or all of your water in either a neem or soap spray formula. Similarly, 2 chopped chili peppers, also available in organic produce sections, can be blended with 1 quart plain water, then strained and used with neem or soap sprays. Wear rubber gloves before chopping hot peppers to avoid burns.

Application

• A spray bottle filled with your homemade solution is usually the only equipment you'll need, but if you have a large garden a backpack sprayer may be useful. For infestations of either bean beetle larvae or adult bean beetles, it's important to spray plant foliage regularly and thoroughly. Coating both the top and undersides of leaves is the best best for controlling beetles and other pests. Spray bean plants every two or three days in the late morning. A non-windy day in which no rain is forecast is ideal. If spraying something with an ingredient that could burn your eyes, such as hot peppers or castile soap, wear safety goggles and keep pets and other people away.