White-Rot Fungus

Dense flower beds are susceptible to fungal diseases.

Some fungi capable of causing white rot include Sclerotinia sclerotiorum, Phanerochaete chrysosporium, Botryosphaeria dothidea and Sclerotium cepivorum. These fungi rot vegetables and fruit, damage flowerbeds and cause persistent root damage. Fungicidal applications are oftentimes effective, but in certain situations soil removal is necessary. Other white-rot fungi are capable of degrading industrial materials and are valued for their recycling potential.

In the Lab

Phanerochaete chrysosporium, also called white-rot fungus, has been tested at the University of Wisconsin where botanists have found it is capable of degrading heavy industrial plastic. These plastics, called phenolic resin plastics, are found in many household building materials. They make up the glue that binds countertops to counters. They hold plywood and particle board in place. They are also found in heavy plastic bowling balls and landline telephones. When these plastics are coated with Phanerochaete chrysosporium, subtle changes occur in the plastic's coloring that indicate decomposition.

In the Garden

Garlic and other underground vegetables are susceptible to Sclerotium cepivorum, a white rot that overwinters in soil. It appears as a cotton-like growth around the base and bulb of the plant.

Botryosphaeria dothidea is a fungal infection that attacks woody plants and trees from birch to apple. The fungus appears as oozing cankers of limbs and bark. White rot fungus overwinters in the canker. When it attacks fruit, it will destroy the fruit's integrity and open it up for further insect attack and degradation.

Other white rots are caused by several different fungi species that present as white growth on the stems, foliage and roots of a wide range of both ornamental and edible crops. Sclerotinia sclerotiorum is capable of staying in the soil and destroying plants as varied as petunias and beans, from the roots up. It can also be carried, via water, to foliage and stems. The rot appears white at first but then hardens into black growths. This fungal infection can eradicate entire flowerbeds.

Treatment and Prevention

Applying fungicides in accordance with manufacturer's directions is an effective means of controlling fungal spread.. Correct dosage amounts, along with dosage times, can effectively prevent and treat damaged crops.

Sclerotinia sclerotiorum can exist in ground soil for as long as four years. Soil removal is the only way to ensure that the fungus will not attack the root systems of newly planted crops. Planting disease-resistant cultivars or letting the soil lay fallow for several growing seasons may reduce the risk.

Powdery mildew and other foliar fungi diseases can be prevented by watering in the morning, rather than at night. This allows the foliage to dry thoroughly before cool temperatures arrive. Cool, moist environments encourage fungal growth.

Considerations

Before planting a garden, take care to monitor your garden's growing conditions. Conduct soil tests to determine the soil's fertility, required fertilizer and amendment application as well as the presence of any soil-borne diseases. Choose plants that are suited for your temperature and humidity. Determine how closely your plants and flowerbeds should be sited to one another. Remember to allow for air circulation and water drainage. If your site or climate tends to have cool night temperatures and humid days, then choose disease-resistant cultivars and plant only those flowers and crops that are recommended for your area.

References

• North Dakota State University; White Mold of Vegetables and Ornamentals; Carol L. Ash, July 1996
• Washington State University Extension; White Rot of Apple; August 21, 2011
• Cornell University Department of Plant Pathology and Plant-Microbe Biology; Diseases of Garlic; Michelle M. Moyer; November 2006
• University of Wisconsin Department of Botany; Tom Volk's Fungus of the Month; February 2007