Holly Diseases and Their Control in the Landscape

Ornamental Disease Note No. 7
D.M. Benson, Plant Pathologist
R.K. Jones, Plant Pathologist (retired)

Hollies are some of the most commonly used plants in the landscape in North Carolina. Japanese holly (Ilex crenata) cultivars such as 'Helleri', 'Rotundifolia', and 'Convexa' are the most widely planted, but unfortunately they have the most disease problems of all hollies.
Black Root Rot

Black root rot, caused by the fungus Thielaviopsis basicola, was first reported on Japanese holly in North Carolina in 1977. The disease has since been found in numerous other locations, both in nursery and landscape plantings throughout the state. This disease has the potential of causing extensive economic and aesthetic losses to this important evergreen shrub in both landscapes and nurseries.

The black root rot fungus has the ability to persist in the soil for many years, even in the absence of susceptible plants. Development of black root rot is favored by high soil moisture and low soil temperatures. The fungus can spread through the soil as mycelium, but its primary means of dispersal is by spores which are carried by water, wind, equipment and infected transplants.

Recommendations for the use of chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by the North Carolina Cooperative Extension Service nor discrimination against similar products or services not mentioned. Individuals who use chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage and examine a current product label before applying any chemical. For assistance, contact your county North Carolina Cooperative Extension Service agent. 04/91/1000

Published by North Carolina Cooperative Extension Service
Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age, or disability. North Carolina State University at Raleigh, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.
Reformatted Dec. 2000 by Plant Disease and Insect Clinic