Only use products that are specifically formulated and labeled for use as insecticide. Most such products are detergents rather than true soaps, which can damage your plants. It is best to purchase a commercial product formulated for use on plants rather than prepare your own spray from dish-washing detergents or other household cleaners because homemade recipes may be more toxic to plants. Some landscape plants known to be sensitive to insecticidal soap are horse chestnut, mountain ash, Japanese maple, sweet gum, jade plant, lantana, gardenia, bleeding heart, sweetpeas, crown-of-thorns and some cultivars of azaleas, begonias, chrysanthemum, fuchsias and impatiens. If uncertain of a plant’s sensitivity, spray a few leaves or flowers first and wait at least three days to watch for symptoms of spray injury, which include yellow, black or brown spots, brown (necrotic) edges on leaf and petal tips, scorch or discoloration. Read the product label for a list of sensitive plants and avoid spraying those. Generally, concentrations of insecticidal soaps exceeding 3% may cause some leaf or flower injury, and concentrations as low as 1.5% may injure sensitive plants. However, on pollinator-attractive plants, spray at dawn or dusk when pollinators are not present. They can be safely used at any time to control pests on plants that are not attractive to pollinators. They are not effective on pests as a residue on the plant surface, and therefore are not toxic to pollinators after the spray dries. Insecticidal soaps are most effective on soft-bodied insects such as aphids, adelgids, lace bugs, leafhoppers, mealybugs, thrips, sawfly larvae, spider mites and whiteflies. Most commercially available insecticidal soaps are made of potassium salts of fatty acids and kill by disrupting the structure and permeability of insect cell membranes. Insecticidal soaps are applied as a foliar application (sprayed on plant leaves) and are effective on a wide range of plant pests when the soap spray comes into contact with the pest. The following types of products have a minimal impact on beneficial insects. However, using these products requires some knowledge about their relative toxicity to beneficial insects and their potential to cause leaf or flower injury (phytotoxicity). Other characteristics of low impact pesticides are those that break down rapidly after application and therefore have minimal impact on pollinators and natural enemies. Low-impact miticides and insecticides not on the EPA Reduced-Risk listĬhoose insecticides that are highly selective to a specific type of insect and so have low toxicity for others (signal word of Caution on the label or EPA Reduced Risk product).Considerations for using certain biopesticides.If you can remove the flowers by mowing or pruning from around the treated plant, and anywhere your application may drift, you can significantly reduce risk to bees and other pollinators. Anything that has flowers or is about to flower is a higher risk than a plant that is past bloom. Second, pollinators are attracted to flowers. First, most bees and other pollinators forage during the day, so if you can spray at night or in the early morning, you can reduce the risk of accidentally spraying them. Some key points about pollinator biology are good to remember if you have to use a pesticide, even if you are only treating one or two trees, shrubs or perennials. Only spray one plant at a time, and only if it is necessary. It is common to see outbreaks of spider mites, aphids and scale insects where pesticides are used. Not only do cover sprays create potential for pesticide runoff and increased human and pet exposure, they actually create pest problems by suppressing predators, parasitoids and diseases that keep plant pests under control. Using preventive cover sprays, where pesticides are sprayed several times a year on a calendar basis, has been shown to create more pest problems than it solves. Pesticides should never be applied unless they are necessary to maintain plant health.
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