A Definitive Guide to Organic Pesticide
Despite the seeming contradiction, organic pesticides have been used on American crops for decades. Some conventional farmers use synthetic pesticides alongside organic ones as a way to maximize crop yields. Backyard gardeners should talk to a local agricultural extension or master gardener's association to discuss viable organic pesticides and their applications to crops and ornamental plants.
Sources of Chemicals
Organic pesticides must come from botanical or mineral sources. Some of these chemicals are highly toxic, but they break down easier than synthetic pesticides. Botanical-based pesticides include nicotine sulfate, sabadilla, rotenone, neem and pyrethrum. Mineral pesticides include sulfur, lime sulfur and copper. Other organic pesticides come from living creatures such as nematodes or bacteria. Spinosad comes from soil bacteria and kills insects and mollusks by disrupting their nervous systems.
Nicotine sulfate derives from the nicotiana species of tobacco plant. The concentrated substance remains highly toxic to mammals, including humans, so farmers should wear protective gloves when applying this powerful chemical. Sabadilla comes from the sabadilla lily plant, and the active ingredient is an alkaloid called veratrine. This dust may cause sneezing and eye irritation, but this organic pesticide remains relatively mild compared to nicotine sulfate. Rotenone derives from the roots of two legumes, and it controls caterpillars, beetles, aphids and thrips that like to feed on the leaves of fruits and vegetables. This substance remains mildly toxic to small mammals, but it also kills fish. Rotenone acts slowly on bugs, but it kills most susceptible insects within a several days of exposure.
Farmers use sulfur to control blights, diseases and spider mites on crops such as potatoes, beans, tomatoes and various fruit-bearing trees. Lime sulfur combines sulfur and lime to kill mildew, blight and some small insects. Farmers combine copper with other pesticides to help fight fungal and bacterial infections in plants.
The key to organic pesticides lies in dosages. Farmers need much higher amounts of organic pesticides to kill insects versus smaller amounts of synthetic varieties. For instance, a farmer may use 10 times as much spinosad on organic lettuce as compared to synthetic pesticides found on conventionally grown produce. Copper, a mineral used to prevent plant diseases on crops, does not pose a harm to humans. However, the substance may build up in soil over time and cause toxicity to plants, worms and other beneficial creatures.
Liquid dishwashing detergents serve as the basis for many homemade insecticides that kill various worms, flies and aphids. The USDA recommends 1 teaspoon of liquid dishwashing detergent mixed with 1 cup of vegetable oil to apply to plants in a home garden. The oil helps the detergent to stick to leaves, while the detergent kills small insects. Gardeners may consider mixing detergent with rubbing alcohol or hot pepper spray in a water base. Pepper sauce stands in for pepper spray on windy days.
Organic pesticides represent chemicals that kill insects and are derived from natural sources rather than from synthetic manufacturing processes. Organic farmers may use these types of pesticides on crops according to rules set forth by the U.S. Department of Agriculture. Organic pesticides have many names, types and forms.