Why Are My Snapdragons Dying?

Do the stems and the undersides of leaves have dusty, dark brown spots on them?

Are the leaves, buds and stems distorted and sticky with clusters of small insects?

Do the leaves and stems of your plant have white, cottony clusters on them?

Are the leaves stippled with yellow, foliage may be webbed?

Are the leaves mottled yellow?

Are the leaves and flowers streaked or mottled, foliage may be spindly and deformed?

Do the leaves have spots on them?

Are the leaves of your snapdragon covered with white powder?

Do the stems have sunken lesions in them?

Likely cause for these symptoms is 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.

Distorted 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 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.

White, cottony clusters on leaves and stems of snapdragons are caused by mealybugs. These tiny insects are covered with a fluffy white coating. They feed by sucking plants sap. They produce sticky substance honeydew which makes leaves sticky. You can control them by washing them off the plant with water spray. Insecticidal soap should be used with severe infestations.

Spider mites often cause problems for snapdragons. 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.

Leaves mottled yellow are caused by whiteflies. These tiny, mothlike flies and their larvae feed by sucking plant juices. Whiteflies secrete honeydew, a sugary substance that makes leaves sticky to the touch. Control whiteflies by eliminating garden weeds and by introducing green lacewings in the garden. Spray infested plants with insecticidal soap every 3 days for 2 weeks.

These symptoms often indicate viral diseases. Viruses circulate internally in plants so there is no effective way of curing the plant. Aphids may spread viruses so the best way of preventing viral diseases is to control these insects.

If your snapdragon leaves have spots on them they are most likely fungal leaf spots. Fungal leaf spots may be brown, black or transparent. Remove and destroy all infected leaves. Thin plants and avoid crowding future plantings. Water snapdragons from below. Clean up all plant debris around your flowers to remove overwintering sites.

White, powdery patches on the leaves are caused by a fungus 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. Any commercial fungicidal spray will protect your plant from further infections.

The most likely cause for these symptoms is Anthracnose. Keep plants dry when watering to prevent spread. Cultural controls such as regular fall cleanup and thinning stem to improve air circulation are effective. Treat severe problems with copper fungicide sprays.

If the stems have girdled, the most likely cause are blights. Several fungi cause blights in snapdragons. Botrytis blight causes shoots to wilt suddenly and fall over, stem bases blacken and rot. Remove and destroy infected plant parts. Don’t put manure near plant crowns, clear mulch from crowns in spring to let the soil dry. Avoid overwatering and wet, poorly drained soil.