Figure 1 - Circular, light tan colored apothecia 2–10 mm diameter (1⁄8 to 1/4 inch) develop from black sclerotia buried to a depth of 5 cm (2 inches) and release ascospores.
Figure 2 - Ascospores colonize blossoms and other senescent plant tissue beneath and within the canopy; infected plant stems, branches and vines become watersoaked and wilted.
Figure 3 - Affected tissues become covered by white, cottony mycelia and sclerotia which darken and harden with age. Tissues dry out and bleach to a nearly white color; the epidermis easily sloughs off when rubbed.
Also affects sunflower, potato, canola and most weeds.
- Infected seed, infested bean and other susceptible host debris from previous seasons
- Rainstorms, dew, fog, irrigation, high fertility
- Moderate temperatures with daily highs less than 30°C [86°F]
Courtesy of H. F. Schwartz & R. M. Harveson [08/09]