Root and stem rots
Pythium spp. (P. aphanidermatum, P. debaryanum, P. ultimum, etc.).
Berberis, Calendula, Chrysanthemum, Delphinium, Dianthus, Gaillardia, Gypsophila, Lathyrus, Lavandula, Lilium, Lupinus, Pelar-gonium, Phlox, Salvia, Sempervivum and Viola.
Wilting, stunting, uneven plant growth, crown rot and plant death. Roots are discolored. The cortex may slough off, leaving the vascular cylinder.
Pythium spp. are soil-borne pathogens, so movement of infested soil or plant material can spread disease. This pathogen produces several types of spores, each with a slightly different function. Sporangia can either germinate and infect plants directly or produce many zoospores. Sporangia may be produced on both above- and below- ground plant parts. Zoospores are motile spores, which allow the fungus to spread in saturated soils or standing water. Each zoospore can cause a new infection. Oospores are thick-walled spores, which allow the fungus to survive on equipment or in soils for long periods of time. Disease can be quickly spread through recirculated irrigation water.
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