Diseases and Insects That May Affect Wave Trailing Petunias

Pythium Fungus

• Pythium fungus is the culprit behind damping-off disease, which causes seedlings to blacken and die. Prevent the fungus by using sterilized pots and fresh potting soil each year for your container-grown plants. Like all petunias, Wave petunias need good air circulation and well-draining soil discouraging fungal diseases like Pythium. Avoid using a sprinkler on Wave petunias in flowerbeds and water early in the day so that the leaves and plant crown dry thoroughly before nightfall. Treat lightly infected plants with a fungicide. Badly infected plants should be pulled and discarded.

Viral Diseases

• Viral diseases deform and stunt Wave petunia leaves, which may become streaked with yellow. The flowers become misshapen and discolored as well. Aphids and other insects spread viral diseases, so an insecticidal-spraying regimen is necessary if these insects are a problem in your garden. Inspect your plants before purchase ensuring they're insect free and don't have any discolored leaves or flowers. There's no chemical control for viral diseases, so infected plants must be pulled and discarded to prevent spread of the disease. Don't put the infected plants in your compost bin.

Aphids

• Tiny, sucking insects that feed on soft new foliage and flower buds, aphids are most common in the spring when many plants are making fast growth. Check your petunias several times a week for aphids, inspecting the underside of the leaves as well as the top. Wash off light infestations with a strong stream of water from the garden hose. Heavier infestations require insecticide. Ask your garden center to recommend an insecticide approved for use in your state.

Other Insects and Diseases

• Cutworms are an occasional problem with seedlings. As the name suggests, these worms chew through the plant stem, cutting it off at ground level. Protect your plants by placing a paper collar around the main stem at planting time. The collar quickly rots away, but not before the stem has hardened enough to discourage cutworms. Crown rot is a problem in poorly drained beds and containers. Never plant Wave petunias in low-lying areas, near downspouts or in containers without good drainage. Other fungal diseases infecting regular petunias are less common on Wave petunias.

Preventing Problems

• The best defense against insect and disease problems is keeping Wave petunias healthy. These problems are more common on plants stressed by bad cultural habits. Grow Wave petunias in full sun in rich, well-draining soil. Space the plants 12 to 24 inches apart so they have good air circulation, and then water them often enough that the soil stays moist but not soggy. Wave petunias are heavy feeders, so give them a slow-release fertilizer when planting or use a water-soluble fertilizer weekly. It's not necessary to remove spent flowers to keep them blooming, but it is a good idea to clean up debris around the plants periodically discouraging insects and disease. Rotate the planting site yearly.