Impatiens have become a mainstay of North American gardens in the past two decades. While their rapid spread by runners and prolific growth minimizes weeds, their ample foliage is a prime target for voracious insects such as aphids, mites and thrips. Here are guidelines on how to protect your cheerful impatiens from these insect pests.
Provide the Healthiest Growing Conditions
Insects prefer to dine on plants that are less than perfectly healthy, so keeping your impatiens in the best soil, light and moisture conditions will circumvent insect infestations. Most species of impatiens prefer partial to dense shade, so keep them out of full sunlight to prevent moisture loss.
Most Common Insect Pests
Aphid attacks are the most common infestation for impatiens. The honeydew the aphids emit will be the first sign that your flowers have fallen prey to aphids. These can be controlled most effectively with natural predators such as lady beetles, lacewing bugs and syrphid flies. Another highly effective predator is the parasitic wasp, which mummifies the aphid after laying its eggs in the aphid's body. Wasps will reduce the aphid population rapidly. Predator insects work much better than using insecticides to control aphids, as the insecticide tends to kill the beneficial insects as well.
Spider and Broad Mites
Another insect that is a menace to impatiens is the mite family, including spider mites and broad mites. Mites will indicate their presence by perforating and sucking fluid from the leaves. Dryness exacerbates mite damage, so keep your impatiens well-watered. You can control mites with many of the same predatory insects that feed on aphids. Pirate bugs, predatory mites and sixspotted thrips can also be added to the natural controls for the spider and broad mite. Predatory mites do not become pests themselves. They will die off from starvation or migrate elsewhere once their food supply of spider mites and broad mites is depleted. You can obtain predatory bugs for your garden at specialty garden centers.
While they are troublesome and cause the leaves of impatiens to look unsightly with white specks or lines across and through them, leafminers seldom do intensive damage to annuals such as impatiens. You can control them with natural enemies, such as the Diglyphus parasitic wasp. It kills leafminers by using them to store its eggs until maturity, and the leafminers become chrysalids for the pupa stage of the wasps. Maintain the plants in their healthiest condition, and clip off leaves that show signs of infestation. Discard or destroy these leaves rather than adding them to compost.
These common grubs are another insect that thrives in dry conditions. They can spread easily from place to place in your garden on tools, garden shoes, and even in the water as it percolates into the soil. They can kill impatiens and other annual plants. Prevent them by purchasing nematode-resistant stock from your garden center, and by keeping soil well-balanced.