Problems with Rudbeckia

Fungal Problems

• Septoria rudbeckiae is a fungus that affects the leaves of Rudbeckia. The infection begins with small, dark brown spots. Ramularia rudbeckiae and Cylindrocladium also cause brown spots, but these appear angular and are not as severe as Septoria. Treat plants before symptoms appear with a preventative fungicide.

  Powdery mildew can cause leaves to drop in extreme cases but often the problem is only cosmetic. To prevent powdery mildew development, thin plants to allow proper air circulation.

Other Diseases

• Angular leaf spot of Rudbeckia comes from bacteria. Symptoms begin on lower leaves as brown spots and move upward. Prevention includes using cultivars resistant to the bacteria. If infection occurs, wait until the hard freeze, and then remove all the plants and leaves. Disinfect tools with a solution of 10 percent household bleach.

  Aster yellows causes unusual symptoms such as leaves sprouting from the cone, dwarfing and yellowing. A bacteria-like organism causes this condition. Once infected, the only recourse is to remove and destroy infected plants. To prevent aster yellows, control leafhoppers, which spread the disease.

Insects

• Aphids cause the most problems with Rudbeckia. Aphids feed on the sap of the plant. A fungus called sooty mold then grows on the honeydew secretions left behind by the insects. The sooty mold interferes with photosynthesis. Shoots and leaves become distorted when aphids gather. Management can include the use of insect predators like lady beetles, washing the aphids off with water from a hose and insecticides.

Best Practices

• Healthy plants can better fight off disease and insect infestations. To prevent problems, start with healthy, well-nourished plants. Pay attention to spacing recommendations, and take into consideration that these plants typically grow 24 to 36" inches high. In the fall, always clean up leaves, stems and any plant debris. Do not dispose of fall cleanup materials in the compost pile, especially if you suspect that a disease has infected them. Water carefully so that it does not splash on the leaves, since this can spread disease.