Insecticide For Zinnias

An annual plant that colors the home landscape with bright blooms from early summer to the first frost, zinnia (Zinnia spp.) is dependable and easy to grow, reports the University of California Agriculture and Natural Resources. Depending on the variety, zinnia is available in demure, 6-inch plants to striking 3-footers. A hardy, drought-tolerant plant, zinnia grows in gardens across the United States with the exception of extreme northern climates and areas with continually soggy soil. Although healthy zinnias are relatively pest-free, they are occasionally bothered by aphids or other plant pests.

Aphids are common insects that damage zinnias when they puncture the leaves and stem to feed on the sap, or juice of the plant, says the University of Illinois Extension. Other pests, such as mites and scales, also damage zinnias by feeding on the sap, reveals the University of Florida IFAS Extension. Sap-sucking pests are tiny and are usually found in dense groupings on the stems or the undersides of leaves. Aphids are usually bright green. Mites are even smaller and look like tiny black dots. Zinnias affected by scales develop small, waxy areas on the leaves. The pests are actually under the waxy substance, where they feed on the plant juices.

Natural predators, especially parasitic wasps, are among the most effective ways to keep aphids, mites and other sap-sucking pests in check. The adult female parasitic wasp, which doesn’t sting humans, lays an egg inside the body of the aphid. When the egg hatches, it feeds on the aphid. Other biological controls include ladybugs and lacewings. Most predatory insects are available at garden centers and nurseries.

Aphids and mites are often removed from zinnia leaves with a forceful stream of water. Prevent mildew by spraying the zinnias early in the day so the leaves have time to dry before evening. Reduce the population of aphids, mites and scale by pinching off affected leaves and stems. Destroy the affected foliage to prevent the pests from spreading. Keep the area under the plants free of debris such as leaves and spent blooms, which provide a hiding place for pests.

Spray zinnias with insecticidal soap or neem oil to kill pests. While insecticidal soap or neem oil kills any beneficial pests that may be on the plant at the time of application, there is no residual affect. Spray the zinnias with a strong stream. Coat the entire plant, including the undersides of the leaves. Other chemical insecticides are effective but should be used only when other measures of control don’t work, as the chemicals kill beneficial insects along with the pests.

Healthy zinnias are more resistant to damage by aphids and other pests. Zinnias require well-drained soil and full sunlight. The plants benefit from light applications of fertilizer applied applied according to the recommendations on the package every four to six weeks. Allow space between plants, as adequate air circulation helps to prevent not only pests, but mildew and other diseases.