Annosus Root Rot (fungus – Heterobasidion annosum): Symptoms of this fungal disease are stunted needle growth, thinning of needles in the crown and eventual death. Roots and butt of stems exhibit a soft, stringy white rot. The fungus may produce perennial conks or fruiting bodies at the base of the tree. The conks vary in shape from a bracket to flat layers. These are gray-brown to dark brown on the upper surface, creamy white underneath, and usually are not casually visible due to covering by needle accumulations. The disease is most serious in planted forests following thinning operations. Infections spread from infected stumps to healthy trees through root grafts. Common borax powder applied in salt shaker manner to surfaces of freshly cut stumps prevents stump infection and subsequent spread to adjacent living trees. A biological control has been developed but is not readily accessible. Harvesting during dry summer and fall months lessens the possibility of new infections.
Brown Spot Needle Blight (fungus – Scirrhia acicola): This disease is a problem on long leaf pine seedlings and Afghan pine grown for Christmas trees. Symptoms first appear as irregularly circular light gray-green spots on needles in the fall. Spots enlarge rapidly and encircle the needle forming narrow tan-brownish bands, and finally the tips of the needles die as a result of multiple infections. Many needles may be killed the first season they are infected. The fungus fruits on very small dark-brown to black colored elongated spots on the dead part of the needle. Spores are produced in wet weather and the needles may be attacked several times in one season. At least three successive annual defoliations must occur to kill longleaf pine seedlings. The best control in longleaf plantations is obtained by controlled winter burning until seedlings are above 18 inches high (the brown spot danger level). In nurseries and on valuable specimen trees apply fungicidal sprays at two week intervals, during humid weather, from April 15 through May.
Cotton Root Rot (fungus – Phymatotrichum omnivorum): Pines grown in alkaline soils are susceptible. Has primarily been a problem on Afghan pine, a species adapted to dry, alkaline soils. (See section on Cotton Root Rot)
Fusiform Rust (fungus – Cronartium fusiforme): A fungus disease with alternate reproductive stages on pine and oak. Symptoms on pine are spherical, oblong or linear swellings or galls on branches or trunks (See Photo). Swellings on trunks may develop into open cankers. Galls rupture in early spring releasing masses of orange spores that infect developing oak leaves (See Photo). Remove galls on specimen trees by pruning. Remove infected trees in planted forests during thinning operations. In nurseries, begin fungicide sprays when oak trees in the area start to leaf out and continue through June. Slash Pine is highly susceptible; longleaf and certain selections of loblolly are moderately resistant.
Needlecast (fungi – Lophodermium sp., Ploiderma lethale, Rhizosphaera sp. and others): Needles may develop dead spots with yellow borders. Eventually needles turn brown and shed (See Photo). Reproductive structures of the invading fungus can often be seen on dead needles. On native pines in East Texas, needlecast is most evident in late spring to early summer when needles shed. When severe, trees have a scorched appearance. Needlecast is not considered a serious disease and no chemical control is advised except on seedlings and highly valued nursery stock or Christmas trees such as Virginia pine.
Table 1: Infection and Symptom Expression of Neddlecast Fungi Attacking Pines in Texas
|Fungus or Disease||Infection||First Symptoms||Needle Shed or Dieback|
|Ploioderma (hypoderma)||Late Spring||Late winter – early spring on one year old needles||Late spring to early summer|
|Lophodermium||Late summer and fall||Yellow spots – late autumn to early spring on one year old needles||Late spring to early summer|
|Rhizosphaera||Spring – on any aged needles||Late summer on first year needles||Browning – late winter. Shed late spring|
Needle Curl (physiological): Ends of needles curl in an abnormal manner. The cause is attributed to water stress.
Needle Rust (fungus – Coleosporium asterum): Present in Texas on loblolly and slash pine. The alternate stage is on various composites, particularly aster and goldenrod. Symptoms on pine are small fragile white “blister-like” structures that erupt through the needle surface. These structures break to release thousands of small pinkish to orange spores. Damage is seldom severe enough to warrant any form of control.
Pitch Canker: (fungus – Fusarium moniliforme f. sp. subglutinans) Cankers usually develop on the main trunk but can occur on lateral branches (See Photo). Copious resin flows from trunk cankers and wood beneath cankers is resin soaked. Resistance and good management practices limit pitch canker development. High nitrogen predisposes pines to infection. Virginia pine, grown for Christmas trees, is more susceptible than most pines.
Seedling Blight or Damping-Off (fungi – Pythium sp., Rhizoctonia sp., Sclerotium sp., Fusarium sp., and Cylindrocladium sp.): These fungi usually live on dead organic matter in the soil but they can become virulent parasites of living plants. They attack young seedlings at, above, or below the soil line. Several things can be done to control damping-off. Locate nurseries on light sandy soils, because damping-off fungi flourish in heavier, wetter soils. Raise seed beds so they will quickly drain after a rain. Mix oak or pine leaf mulch into the seed beds to about two percent of soil volume. Mulch the seed beds with pine needles. Fumigate soil prior to planting with methyl bromide or other approved soil fumigant. Treat the seeds with a seed protectant fungicide.
Sphaeropsis Blight (fungus – Sphaeropis sapinea): Was called Diplodia blight until name was changed in 1980. Presently, Sphaeropis blight only is considered significant on Afghan pine grown for Christmas trees in the western part of Texas. Infection takes place in spring under wet conditions. Causes severe shoot dieback (See Photo). Chemical control has not been highly effective.
Wood Rots (fungi): Discoloration, softening, crumbling and disintegration of wood may be caused by a variety of fungi. Prevent damage from fire, insects, machinery and unfavorable environmental situations. Remove diseased trees. Plant trees adapted to the locality. Avoid introducing foreign species of trees unless inspected and approved by forestry personnel.