What Is Wrong With My Tithonia?

Are there any small, round reddish brown spots with white to grey centers on the upper surface of the leaves?

Are the leaves yellowing, wilting and, dying?

Are the leaves mottled with dark green?

Are the leaves curled and distorted?

Do the leaves have large, ragged holes in them?

These symptoms indicate Alternaria leaf spot. Warm, wet conditions favor this fungal disease. Spray infected plants with copper and/or sulfur to prevent further disease development. Plant only pathogen-free seed from a reputable nursery.

Yellow leaves that wilt and die usually indicate Root rot. Several pathogens cause root rots of seedlings as well as mature plants. Poorly drained, overly wet soil promotes rot so choose well-drained sites and add organic matter to improve drainage. Remove and destroy infected plants. Solarize the soil before replanting.

Mottled or streaked leaves are caused by Mosaic Virus. There is no cure for infected plants. Remove and destroy all flowers that have the symptoms of the mosaic virus. Mosaic virus is spread by aphids, so the best way of preventing the disease is to control these insects.

Distorted and curled leaves are caused by aphids. These tiny insects cluster under leaves and on growing tips where they feed on plant sap. Leaves, stems, and buds get distorted and later leaves and flowers drop from the plant. You can control them by washing them off the plant with water spray. Insecticidal soap should be used with severe infestations.

Large, ragged holes in the leaves are caused by slugs and snails. Slugs and snails feed on the plant leaves usually at night. To control slugs and snails use diatomaceous earth around your plants. You can also handpick them during the night or use shallow dishes filled with beer as a trap.

Spider mites are known to cause problems for tithonia. They suck on the plant juices removing chlorophyll and injecting toxins which cause white dots on the foliage. There is often webbing visible on the plant. Hose off plants when symptoms first appear. A strong stream knocks mites off plants and may give control. Introduce predatory mites. For severe infestations, spray plants with insecticidal soap or pyrethrin.