AboutJohn Cawly Expertise I can help with identification and possible treatment of plant diseases that affect houseplants and horticultural species, to include both biological (fungal, bacterial, viral, parasitic etc.) and environmental/cultural (watering, potting media, etc.) aspects.
Experience Practical experience with a wide variety of houseplants and greenhouse plants, including cacti, euphorbia, african violets, amaryllus, and many others.
Organizations American Phytopathology Society
American Society of Plant Biologists
American Society for Virology
Publications Molecular Plant Microbe Interactions
Proceedings of the National Academy of Science (in print)
Rhodora -- Journal of the New England Botanical Society
Allelopathy Journal
Education/Credentials BS, Southern Illinois University - Biological Sciences MS, Southern Illinois University -- Biological Sciences - Genetic Engineering Specialization PhD, University of Missouri Columbia -- Plant Microbiology and Pathology (Viral Diseases specialization/Biotechnology Emphasis)
Question Dear John, We have black eyed susans planted at various places on our property, and on every one of them, our foliage starts out well, and then gets all brown spotted and then dries up and dies. until the end of summer the flower is there, but the foliage is pretty much dead.
Answer Hi Debra,
The most common pests/diseases that affect Rubeckia species are: aphids, which suck sap from the plants and coat the leaves with
sticky honeydew; goldenglow sawfly, the larvae of which may completely defoliate plants; Four-lined plant bugs which cause round, brown, sunken spots, sometimes mistaken for a disease.
Downy mildew causes seedlings to wilt and die. On older plants the foliage is mottled light yellow. Several leaf spots may be found but are not serious. Remove and destroy infected leaves. Powdery mildew may cause a white powdery growth on the leaves in late summer. White smut causes light spots on the leaves. Destroy plant residues in the fall and get rid of infected plants as they are noticed. Verticillium wilt may kill Rudbeckia spp. Verticillium wilt causes the plant to collapse almost overnight, with a greatly reduced ability to conduct water through the plant. No amount of watering will help afflicted plants.
From your e-mail, I got the sense that this occurs every season. If that is correct then follow the guidelines above for cleaning the beds in the fall of all debris which would surely contain inoculum for the next growing season.
As long as the plants are flowering and the roots are not affected, then the plant is not severely endangered.
