Plant Disease Management Handbook

Cause Albugo candida, a fungus-like microorganism, can cause disease on cruciferous plants including rapeseed, broccoli, cabbage, radish, and wild mustards. In the Pacific Northwest, white rust can be severe on crucifer seed crops. The pathogen overwinters as oospores in stagheads (galls formed on infected seed heads) or plant debris as well as mycelium in infected hosts. Pieces of staghorns are often found as seed contaminants and can be the primary source of infection in a field.

By C. M. Ocamb

Cause Damping-off can be caused by Pythium spp., Fusarium spp., Rhizoctonia solani, Alternaria spp., and other fungi. These soilborne pathogens attack young seedlings of many vegetables in the Willamette Valley, including members of the genus Brassica, as well as cause root rot of more mature plants. These soilborne fungi can persist indefinitely in soil or plant debris.

By C. M. Ocamb

Cause Fusarium spp., Phytophthora megasperma, Pythium spp., Rhizoctonia solani, and other fungi. These microorganisms can survive in soil for many years. Wind and water can move infested soil and plant debris. The disease is favored by extremes in soil moisture (too dry or too wet). Anything, which impedes root growth such as cold or compacted soils also favors the disease.

Cause The fungus, Botrytis cinerea, is an opportunistic pathogen that easily invades weak, damaged, or senescing tissue. Disease usually starts on senescing flowers and flower infections are important for subsequent spread to leaves and pods. Spores (conidia) are produced throughout the growing season under a wide range of temperatures and humidity, and stem infections are a durable inoculum source, producing conidia throughout bloom.

By C. M. Ocamb

By C. M. Ocamb

By C. M. Ocamb

By C. M. Ocamb