Vegetable Program
Disease Management

Bean Sclerotina Blight

White Mold of Beans

White mold of beans is caused by Sclerotinia sclerotiorum, which also causes disease on more than 360 different plant species. It is a major disease of beans world wide, particularly in cool, moist regions and can result in complete crop loss. Sclerotinia overwinters in the soil as sclerotia (small, black resting structures) and can persist there for 5-8 years. The fungus is favored by cool, moist weather, high humidity, and long periods of leaf wetness.

White mold of beans develops after or during the flowering period, as the fungus needs the senescing tissue for nutrition to begin the infection process. All aerial parts of the plants including pods and seeds may be attacked. Initial lesions are small, circular, water-soaked and light green but rapidly increase in size. Affected tissues dry, turn brown, and may be covered with a white, cottony mycelium. Sclerotia form in infected tissue and entire branches or plants may be killed.  

Management

Deep plowing and crop rotation are of limited value because of the wide host range of the pathogen and its ability to persist in the soil for extended periods. Sclerotia buried by deep plowing may subsequently emerge at soil surface with later plowings. Losses of fresh pods can be minimized by timely harvesting, rapid cooling, and storage under refrigeration. White mold is more severe where the plant canopy is dense; reduction in canopy density can be achieved by increases in row width, plant spacing, cultivar selection, and careful attention to nitrogen levels.

• Reduce humidity and high moisture periods within the field by orienting rows in the direction of prevailing winds, avoiding excessive irrigation after petal fall, and timing irrigation to allow plants to dry before nightfall.
• Rotate with nonhosts for up to 8 years. Nonhosts include grasses, cereals, and onions.
• In fields with a history of White mold, apply fungicides at 1-10 % bloom. A second application may be necessary under heavy disease pressure.

Chemical recommendations:

boscalid (Endura): 8 to 11 oz/A. (REI 12 h, dh 7 d. Group 7). Do not make more than two applications of Endura per season.

iprodione (Rovral): 1.5 to 2.0 lb/A. (REI12 h, Group 7). Do not make more than two applications per season, with the last application no later than peak bloom. Do not allow foraging until 14 days after application.

thiophanate-methyl (Topsin M 70 WP): 1 to 1.5 lb/A. (REI 12 h, dh 14 d, Group 1).

References

Howard, R.J. et.al., eds.1994. Diseases and Pests of Vegetable Crops in Canada. Canadian Phytopathological Society.554 pp.

Bean, Snap (Phaseolus vulgaris)—White Mold ( Sclerotinia Blight). http://plant-disease.ippc.orst.edu/disease .

For Current information on production methods (including varieties, spacing, seeding, and fertility), weed, disease, and insect management, please visit the New England Vegetable Management Guide website.

Below you will find additional information on managing this crop, including photos of insects and diseases in this crop, fact sheets, articles, and power point presentations, when available.