Insecticides offer control over the pesky flies you find on your plants. Some flies are harmless and actually somewhat beneficial to your soil. Others, however, cause damage to your garden or house plants. In either case, flies are considered an annoying pest that most gardening enthusiasts would rather do without.
Before applying an insecticide to your plants or plant soil, identify the type of flies you're dealing with. If you're at a loss, capture some in a sealed container like a plastic bag and contact a licensed professional or local county extension agent for assistance.
Fungus gnats are one common type of fly found in potted plants like African violets and salvia as well as outdoors, according to the Oregon State University Extension. Whiteflies are another type found indoors and outdoors on ornamental plants and vegetables, according to the University of Missouri Extension.
Fungus gnats are very small flies that don't bite. These flies display gray bodies and live in, feed on and reproduce in organic content like mulch or soil, whether indoors or outdoors, according to the Oregon State University Extension. They often appear when watering a plant when it flies out of the soil to avoid the incoming water.
Whiteflies resemble tiny moths with white-hued bodies about 1/10 to 1/16 inches in length. They reproduce and feed on plant surfaces. When you touch or jar the plant, the flies take flight, creating dense airborne populations that look like white puffs, the University of Missouri Extension says.
Insecticides offer protection against the damage flies cause to your plants. Fungus gnats are often just an annoying pest that help decompose organic content in soil. Certain species, though, feed on above-ground plant parts as well as roots, leading to wilted or dead plants, the Oregon State University Extension says. Whiteflies are sucking bugs that insert their mouths into plant surfaces, extracting tissue fluid. Whiteflies produce honeydew, a sugary substance, while they feed. This substance creates an ideal environment for a fungal disease called sooty mold. Feeding causes yellowing and wilting of leaves and defoliation, the University of Missouri Extension says.
For chemical control of fungus gnats and whiteflies in your plants, use an insecticide with the active ingredient pyrethrin. For fungus gnats, apply the insecticide to the surface of your plant's soil. Apply to the lower surface of your plant's leaves for whiteflies. Other insecticides include insecticidal soap, malathion and permethrin, the University of Missouri Extension says. For best results, apply insecticides once a week for up to five weeks.
Insecticides are more effective when your plant is well cared for. Maintain your plants according to their requirements like sun exposure needs, soil type and appropriate watering. Additionally, insecticides contain harmful toxins. Use insecticides as a last resort for problemsy. Natural control includes using of natural enemies. Whiteflies, for example, are hunted and killed by enemies like lady beetles found through garden supply catalogs, online or in stores. For fungus gnats, the bacterial disease Bacillus thuringiensis subspecies Israelensis infects flies without harming your plants or the environment.