Delphiniums In My Garden Are Attacked By Some Insects Or Fungi? How Can I Defend Them From Attackers?

Are the leaves, stems, and buds distorted and sticky to the touch?

Do the leaves have tan or brown blotches or serpentine tunnels?

Do the leaves on your plants have large, ragged holes?

Do the leaves of your delphiniums have powdery white patches on them?

Are the leaves on your delphinium wilting while stems exude a sawdust-like material and brakes easily?

Are the leaves on your delphiniums stippled with reddish to yellow and the foliage is webbed?

Have the stems blackened at the base and does the whole plant falls over?

Distorted and sticky leaves, stems and buds are caused by aphids. These tiny insects can vary in color, green, pink, black, gray to completely white. They cluster under leaves and on growing tips where they feed on plant sap. Leaves, stems, and buds get distorted and latter 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 only with severe infestations.

These symptoms are usually caused by insects - Leafminers. These tiny pale green fly larvae feed between the upper and lower surfaces of the leaves. Prune off and destroy all infested leaves. Remove debris in fall because it might contain overwintering leafminers. The weekly application of insecticidal soap should keep their numbers low. Also, introducing parasitic wasps is a very effective method of controlling leafminers.

Large, ragged holes on 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. This will irritate their soft bodies and their numbers will drop. You can also handpick them during the night or use shallow dishes filled with beer as traps.

White, powdery patches on the leaves are caused by a fungal disease - Powdery mildew. Powdery mildew usually appears in damp places. Thin your plants to ensure good airflow. Water plants from bellow to keep foliage dry. Any affected leaves should be cut off and removed. Any commercial fungicidal spray will protect your plant from further infections.

These symptoms usually indicate caterpillars - Borers.

Redish to yellow flecks on leaves and webbed foliage is caused by spider mites. These tiny, spider-like pests feed by sucking sap from the underside of the plants leaves causing yellow flecking on the upper leaf surfaces. You can control spider mites by spraying plants thoroughly with water 2-3 times a day for several days. For severe infestations, spray plants with insecticidal soap, or pyrethrin as a last resort.

Blackened base of the stems is most likely caused by Crown or Root rot. These diseases are caused by both fungi and bacterias. Poorly drained, overly wet soil promotes rot so choose well-drained sites and add organic matter to improve drainage. Avoid injury to crowns when digging near plants. Keep winter mulch away from crowns. Remove and destroy infected plants. Solarize the soil before replanting.

If the leaves have yellow, brown or black spots on them, the most likely cause is fungi. Dig and destroy seriously infected plants. Keep the garden free of debris, and cut plants to the ground at the end of the growing season. Apply preventive sulfur sprays if the leaf spot is a serious problem.