How to Kill Gnats & Insects on a Plant

Treat your plants with a pesticide. Pesticides are available in organic and conventional varieties. Choose a product formulated specifically for the type of pest you wish to treat and that is labeled safe for the types of plants you grow. Follow label instructions for use of the product for best results.

Apply a dose of Bacillus thuringiensissubsp bacteria to your plants. This bacteria is harmful to parasitic plant pests such as mites, gnats, aphids and worms, killing them and eliminating them from your plants. However, it is not harmful to humans or animals. BT is available in most garden supply stores.

Apply a soap spray to your garden. These sprays may be purchased in stores or created at home using water and dish soap in a pump sprayer. Spray both the tops and undersides of leaves to kill any insects along with their eggs and larvae.

Introduce beneficial insects into your garden. These insects prey on harmful insects without damaging your plants. Beneficial insects include assassin bugs, soldier beetles and lady beetles.

Clean up your garden. Remove any weeds in your plants or on plant bed borders. Provide proper irrigation and drainage in your garden to prevent standing water and discourage insect activity. Fertilize your plants and soil to strengthen your garden against pest attacks. Remove mulch, rocks and badly infested plants, replacing them with clean mulch, rocks and fresh plants.