My Helianthus Is Wilting

Preventive Care

• Provide regular care to your sunflowers; healthy plants have a greater ability to handle disease than weakened plants. Maintain moist, well-drained soil high in organic content. Plant these sun lovers in areas of your landscape that receive full sun exposure for best development and color; allow for a minimum of 6 hours of daily direct sunlight to avoid top-heavy plants. Lay a 2- to-3-inch layer of mulch to the soil surrounding Helianthus plants without pushing the mulch against the stalks. Use an organic mulch like leaves or grass clippings to prevent weed growth and retain water.

Sclerotinia Disease

• Sclerotinia disease is a fungal infection that leads to wilt on Helianthus plants. Caused by the fungal pathogen "Sclerotinia sclerotiorum," this disease causes a variety of problems, including wilt with root infection. Sclerotinia also attacks the head and stalk. Also referred to as white mold, this problem is soil-borne, meaning it is already present in soil before the flowers are planted. Infection activity occurs during summer. When sclerotinia wilt infects Helianthus plants, it results in a fast onset of leaf wilt. Wilting typically occurs from the seedling phase until just before flowers bloom. The bottom of stems near the soil line exhibit a wet appearance; in moist conditions, a white mold forms as roots decay.

Verticillium Wilt

• Verticillium wilt, caused by the fungal pathogen "Verticillium dahliae," targets a variety of hosts, including sunflowers, snapdragons and dahlias. Another soil-borne disease, verticillium wilt is most active in cool weather, but can continue growing at temperatures that surpass 90 degrees Fahrenheit. Verticillium wilt on sunflowers begins as yellowing leaves that become more discolored until the leaf tissue dies. The disease attacks leaves toward the bottom of the plant first, working its way up toward the blossom. Stalks then exhibit discoloration in streaks of brown to black. Verticillium wilt affects all parts of the sunflower, from the roots to the blooms.

Solutions

• Control of wilting diseases involves avoidance, as there are no available cures once sunflowers are infected with sclerotinia or verticillium wilt. Purchase healthy plants from reliable sources, and have your soil tested for fungal pathogens before planting Helianthus. Contact your local county extension agent for assistance regarding soil tests. Sanitize tools like pruning shears between each cut to prevent the spread of disease. For sclerotinia management, rotate sunflowers out for three to five years for minor infections and up to eight years for severe issues. Rotate to non-host crops for three to four years with verticillium wilt management. Consult a professional for an accurate diagnosis.