Why Does My Penstemon Look Sickly?

Are there any small, necrotic flecks on leaves that develop a chlorotic halo and expand into tan brown necrotic spots?

Are the flowers covered with gray mold, leaves may be blotched or discolored?

Are there any small, angular, gray-brown spots with defined darker red-brown margins on leaves?

Are there any rust-colored spots on foliage?

Are the leaves covered with white powder?

Are the leaves discolored, fine webbing may be present?

Are the leaves curled and distorted?

Do the leaves have large, ragged holes in them?

Are the leaves covered in coarse stippling and may appear silvery?

Cercospora leaf blight is caused by a fungus that can be introduced through an infected seed and spread by wind or water splash. Plant only pathogen-free seed from a reputable nursery. Apply copper-based foliar fungicide if the disease emerges. Keep the area clean and be sure to dispose of plant debris.

Gray mold on flowers is probably caused by fungal disease - Botrytis blight. You can prevent Botrytis blight disease by planting in areas with good air circulation. Water plants sparsely. Severely infected plants should be removed. Spray weekly with a copper fungicide until the disease is under control.

These symptoms indicate fungal disease - Septoria leaf spot. Remove and destroy infected plant debris. Don't handle or brush against plants when they are wet. Rotate plantings. Remove weeds growing nearby.

Rust-colored spots on foliage indicate a fungal disease - Rust. Provide good air circulation around plants by thining them. Avoid making leaves wet when watering. All infected leaves should be removed. Spray leaves with sulfur early in the season to prevent rust or to treat mild infections.

White, powdery patches on the leaves are caused by a fungal disease Powdery mildew. Powdery mildew usually appears in damp places. Encourage good air circulation around the affected plants by thining them and any surrounding plants. Water plants from bellow to keep foliage dry. Any affected leaves should be cut off and removed. The appropriate fungicidal spray will protect your plant from further infections.

Spider mites are known to cause problems for Penstemon plants. 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.

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.

These symptoms may indicate thrips. Thrips are tiny, yellow to black flying insects. Severely infected plant parts should be removed and destroyed. Control thrips by introducing lady beetles or lacewings, their natural predators. Insecticidal soap helps in severe infestations.

If the leaves and flowers have been eaten the culprits are Japanese beetles, pests that can seriously damage foliage. Adults of these insects devour leaves, stalks, and flowers of nearly 300 plant species. Their larvae feed on the roots of the plants. Handpick adult beetles into a can of soapy water but make sure to wear gloves as Japanese beetles are blister beetles. Apply parasitic nematodes to the soil to limit beetle grub populations. Use pyrethrin powder or neem oil as a last resort.