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Publication #FOR238

Red Root and Butt Rot of Sand Pine1

Marc Hughes and Jason Smith2

Overview:

Sand pine (Pinus clausa (Chapm. ex Engelm.) Vasey ex Sarg. ) is a native conifer with a natural distribution almost exclusively confined to the state of Florida. This pine is a slow grower compared to other native pines, but it can reach 100 feet at full maturity with an irregular and often open crown (3). There are two varieties of sand pine, Ocala and Choctawhatchee. The Ocala variety (P. clausa var. clausa Ward) is found in much of the Florida peninsula, while the Choctawhatchee variety (P. clausa var. immuginata Ward) is naturally limited to portions of the state's western panhandle and coastal Alabama (2). This evergreen conifer has the ability to grow in infertile, acidic, deep, and sandy soils. Red root and butt rot has become an important root disease of mature and over-mature sand pines in plantations and natural stands (2). The disease is caused by the basidiomycete fungus Onnia circinata, (formerly Inonotus circinatus). The fungus presumably enters the host tree through direct contact with infected roots or by way of basidiospores that land on wounded roots or root collars (1). The fungal hyphae colonize the roots of the tree and over time cause a characteristic white pocket rot. (A fungal decay that decomposes the wood's lignin, hemicellulose, and cellulose that occurs in white pockets or streaks separated by thin areas of firm wood). Affected trees are marked by a decrease in growth, thin/chlorotic foliage, root resinosis, death, and windthrow (4).

Causal Agent

Onnia circinata is the predominant root pathogen associated with red root and butt rot disease of sand (Pinus clausa) and slash pine (Pinus elliotti) (1); however, some believe this to be a disease complex because of its association with other root pathogens ( including Armillaria tabescens, Heterobasidion annosum, Leptographium procerum, and Phytophthora cinnamomi) (2,4). O. circinata is a basidiomycete (mushroom fungi) that can live as mycelium (vegetative mass of fungal growth) in diseased roots or as a basidiocarp (fruiting structure/conk). O. circinata survives vegetatively in the roots and in the bases of stems of infected trees; it reproduces and is disseminated by means of spores produced by readily identifiable basidiocarps (Figure 1). When fresh and mature, the solitary basidiocarp (conk) typically appears in the autumn and is stalked when emerging from the soil or roots and sessile (non-talked) if attached to the tree butt/stump. The basidiocarp is about 18cm wide, and when fresh is spongy to leathery. The basidiocarp has a rusty tan upper surface and can be fringed with bright yellow margins. The conk's lower surface has a yellow to brown underside (4) (Fig. 1).

Figure 1. 

Fruiting bodies of O. circinata produced on sand pine in Florida. (Photo Credit: Dr. Ed Barnard, Florida Division of Forestry, Florida Department of Agricultural and Consumer Services)


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Symptoms and Signs

Due to the root damage caused by O. circinata, the above-ground symptoms include: diminished growth with crown thinning, chlorotic foliage, and mortality. Tree death is usually caused by significant root loss, which can lead to windthrow. Stem decay can cause the pines to break off at the butt, or base, of the tree. The underground symptoms include resin-soaked roots that can form encrustations when mixed with soil. Dissection typically reveals reddish/brown wood, which advances to the characteristic white pocket rot, which turns the wood soft (1,2,4) (Fig. 2).

The only sign for red root and butt rot of sand pine is the solitary or often grouped basidiocarps that form in the autumn. The sessile basidiocarp can be seen on the butts and stumps, and the stalked form appears on infected roots (1,4).

Figure 2. 

White pocket rot caused by O. circinata as illustrated by this sand pine root. (Photo Credit: Dr. George Blakeslee, School of Forest Resources and Conservation, University of Florida)


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Disease Cycle

The disease is presumably initiated when hyphae from infected roots come into contact with healthy roots by surface rubbing, root grafting, or when airborne basidiospores come into contact with wounded roots or root flares. The infection then spreads into the root system and butt of the tree, causing white pocket rot. The lifecycle is completed when the pathogen infects a new host via root graft or when the basidiocarps are formed (1, 4).

Management

There has been little research in the management of stands infected by O. circinata. As with many forest root diseases, the key to management is the prevention of disease occurrence. When planning a stand, the most important step is to suit the species of tree to the site conditions. In order to minimize stress, plant sand pines only in sites with very deep, well drained, sandy soils. Overly dense stands may cause competition stress, which can also predispose the tree to disease. Some people think that using the Choctawhatchee variety will help reduce root disease, but this has not been substantiated through research. If too many trees are dying, consider a salvage harvest to curtail losses. Remove infected root material and basidiocarps to reduce future inoculum and help to reduce future disease severity on the site.

References

  1. Barnard, E. L. 2000. Inonotus root and butt rot of pines in Florida. Plant Pathology Circular. No. 403. University of Florida, Gainesville.

  2. Barnard, E. L., G. M. Blakeslee, J. T. English, S. W. Oak, and R. L. Anderson. 1985. Pathogenic fungi associated with sand pine root disease in Florida. Plant Dis. 1985, 69(3):196–9.

  3. Gilman, E. F. and D. G. Watson. 2006. Pinus Clausa: Sand Pine. 2006. University of Florida, Institute of Food and Agricultural Services, Gainesville. EHN-617. http://edis.ifas.ufl.edu/ST458. Accessed 3/15/09.

  4. Sinclair, W. and H. Lyons. 2005. Diseases of trees and shrubs. 2nd ed. Cornell University Press. Ithaca, New York.

Footnotes

1.

This document is FOR238, one of a series of the School of Forest Resources and Conservation Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date May 2010. Reviewed June 2013. Visit the EDIS website at http://edis.ifas.ufl.edu.

2.

Marc Hughes, graduate research assistant, Plant Pathology Department; and Jason Smith, forest pathologist/state forest health Extension specialist, School of Forest Resources and Conservation, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611.


The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county's UF/IFAS Extension office.

U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.