Pine Insects

Southern Pine Beetle (Dendroctonus frontalis):  The southern pine beetle (SPB) is the most important pest of southern pines in North America.  SPB is present throughout the southern pine ecosystem, often in low (endemic) populations.  However, every decade or so SPB populations outbreak and can cause widespread mortality in southern pines.  Multiple generations can occur each year.  SPB adults are small, about 2-3 mm long and dark black.  When SPB attack trees they bore into the phloem, where adults create S-shaped galleries and lay eggs.  Larvae develop in the galleries, and when a high number of larvae feed on the phloem of a single tree, that tree may be killed.  Adults also introduce blue-stain fungi into attacked trees.  There are several natural enemies that help keep SPB populations in check.  Currently, proper stand management (i.e. stand thinning, prescribed fires) is the best way to maintain resistance to SPB in your pine stands.  For more information see Clarke and Nowak (2009).

Ips beetles:  There are three species of Ips bark beetles in the southeastern U.S. that cause noticeable damage to southern pines: the small southern pine engraver (Ips avulsus), the eastern six-spined engraver (Ips calligraphus) and the eastern five-spined engraver (Ips grandicollis).  Ips beetles can be identified by the presence of spines on their posterior end.  Ips adults usually only attack weak or dying trees, but windstorms, drought, or lightening can weaken trees and create suitable habitat for Ips populations.  In some cases, healthy trees can be attacked by Ips beetles.  In fact, the only insect that kills more timber in the southeastern U.S. is the SPB.  Ips beetles create small pitch tubes and Y, X, or H-shaped galleries in the phloem of the tree.  Ips will breed in logging debris, dead tree tops, or any other dead or dying tree material.  The best management for Ips beetles is the maintenance of healthy forest stands.  For more information see Gandhi and Miller 2009.

Hylastes beetles:  Three species of Hylastes bark beetles are commonly encountered in the southeastern U.S.: Hylastes porculus, Hylastes salebrosus, and Hylastes tenuis.  Hylastes opacus, an exotic species, is rarely collected.  These beetles are known secondary pests, and are not implicated as primary mortality agents in southern pines.  Hylastes species live and breed in dying and dead trees, and are often mistakenly blamed for tree mortality.  Adults will lay eggs in large roots, where larvae will develop by feeding on the phloem.  Management recommendations for these insects involve maintaining healthy trees.

Black turpentine beetle (Dendroctonus terebrans):  The black turpentine beetle (BTB) is much larger than the SPB (adult BTB are ~5-6 mm long), and is generally considered a secondary pest of pines in the southeastern U.S.  BTB attack the lower portion of the tree, usually in the lower 15 feet of stem.  BTB may also attack large roots.  Healthy trees are rarely attacked; BTB usually attacks weakened or damaged trees, such as those affected by fusiform rust or exhibiting damage from harvesting equipment.  The BTB creates large, easily visible pitch tubes (~1” in diameter).  Adults do not create extensive galleries, and larvae tend to develop in “pockets” under the bark.  Treatment options are limited, but good stand management will generally keep trees healthy and resistant to BTB attack.  For more information see Staeben et al. (2010).

Deodar weevil (Pissodes nemorensis): The deodar weevil is found throughout the southeastern U.S.  This beetle commonly attacks weakened or dying pine trees, especially those stressed by overstocking, drought, or mechanical damage.  Adults feed on terminals or foliage, while larvae feed in the phloem.  Larvae pupate in “chip cocoons” under the bark.  These beetles are a secondary pest and rarely cause economic damage.  Proper stand management will likely eliminate any potential problems from these insects.

Pine Diseases and Associated Fungi

Annosum root rot: Also called Fomes root disease, this malady is caused by the fungus Heterobasidion irregulare. Infected trees may have thin crowns, resinosus near the base or coarse roots, or actual mortality. Fungal spores are spread through the air, and enter a tree through wounds on the lower stem or large roots. Once the fungus has established in dead or dying trees, it can grow through root grafts and infect healthy trees. In the southern U.S., soils that are sandy or sandy loam, have good drainage, and are generally dry are considered high hazard sites. Management strategies include thinning in summer time using granular borax on stumps after harvest. For more information see Dreaden and Smith (2010).

Fusiform rust Fusiform rust (Cronartium quercuum f. sp. fusiforme) is the most serious disease affecting southern pines, particularly loblolly and slash pine.  Galls resulting from fusiform rust infection can weaken stems and branches, rendering them susceptible to breakage.  This fungus has a complex life-cycle, and requires an alternate host often in the black or red oak group.  Foresters and geneticists have successfully bred resistance to fusiform rust into certain pine cultivars.  Management can include fungicides in nurseries, but the only management for older forests is to plant seedlings resistant to fusiform rust.  For more information see Phelps and Czabator (1978).

Leptographium root fungi: This is a large, diverse group of root-infesting fungi.  Leptographium wageneri, a species found in western U.S., causes black stain root disease, and can kill healthy, live trees.  Black stain root disease can affect Piñon pine and Douglas-fir.  In the southeastern U.S., several Leptographium spp. fungi are known to infect weak, dying, or dead southern pines.  These fungi are known secondary pathogens, which are vectored into wounds on the tree in coarse roots or the lower stem by several species of root-feeding beetles.  These fungi have a complex life cycle.  There is no management for these fungi, as these species only infect weakened trees.  Therefore, maintaining a healthy forest stand should ensure proper management of these fungi. For more information see Barnard and Meeker (1995).

Littleleaf disease: Phytophthora cinnamomi causes this serious disease in older shortleaf pines. Trees rarely live past a few years once infected. Early symptoms include thin crowns, needle loss, and general sickly appearance. Shortly before tree death, large crops of small cones are often produced. This disease is most common on moist soils, and can be avoided by planting non-susceptible pine species. Silviculturally, subsoil breakage to allow better root growth and increased drainage can help trees overcome this disease. Alternately, techniques such as tree removal or fertilization to increase tree vigor can be used to control littleleaf disease. For more information see Mistretta (1984).

Pitch canker: Pitch canker is caused by the fungus Fusarium circinatum, and usually infects older trees. Fungal spores are spread by wind and rain, and generally only infect trees at wound sites. The fungus kills shoots and needles, resulting in branch flagging and cankers. Pitch canker can be problematic on pine roots in nurseries. Maintaining tree vigor and health is the best way to manage for this disease. For more information see Barnard and Blakeslee (2006).

Southern Pines

Loblolly pine: Loblolly pine (Pinus taeda) is the most commercially important tree species in the southern U.S.  Loblolly pine will grow across the entire southern U.S., with the exception of very wet or infertile sites.  These trees are shade tolerant, grow readily with hardwoods, and are extremely prolific.  No other tree species in the southern U.S. has had their growth and productivity improved so much over the last several decades due to the enormous amount of silvicultural and genetic research.  Loblolly pine responds well to silvicultural treatments, and proper stand management – on small tracts of land and area-wide – can greatly improve growth, health, and pest resistance.  For more information see Gordon and Langdon (1990).

Longleaf pine: Longleaf pine (Pinus palustris) is an ecologically important southern pine species. This tree’s natural range is deep, sandy Coastal Plain soils, and the tree spends its first several years growing a taproot (i.e. the grass stage). Much of longleaf pine’s natural range has been planted with loblolly pine, but in the last decade efforts have been made to re-establish longleaf pine in its natural habitat. Longleaf pine trees require frequent, low intensity fires for survival. In fact, fire suppression efforts have led to the decline of the longleaf pine/wiregrass ecosystem. This tree is intolerant to competition, and has a deep taproot, making it able to survive on sandy soils. The tree is used by wildlife, especially the endangered red-cockaded woodpecker. For more information see Boyer (1990).

Slash pine: Slash pine (Pinus elliottii) has the smallest natural range of the southern pines, growing naturally in wet areas in the Gulf Coast region. This tree species grows rapidly, and has an extensive lateral root system. Slash pine has been planted in plantations across the southern U.S. Slash pine is shade intolerant, and does not compete well with other vegetation. Slash pine was commonly used for naval stores, as this species produces copious amounts of sap. For more information see Lohrey and Kossuth (1990).

Shortleaf pine: Shortleaf pine (Pinus echinata) is widely distributed across the southeastern U.S., and is commonly grown in the western and northern parts of the southern pine range. Shortleaf pine grows best on deep, well-drained sandy loam or silty loam soils; shallow, rocky soils are not preferred. Shortleaf pine has a large root system, and lower nutrient demand than loblolly pine. Shortleaf pine is slower-growing compared to other southern pines, with a typical rotation age of 55-60 years. This species is shade intolerant, and does not compete well with other vegetation when young. For more information see Lawson (1990).

Invasive Plants and Competing Vegetation

Cogongrass: Cogongrass (Imperata cylindrica) is an invasive plant occurring over much of the southeastern U.S.  This plant is considered one of the worst invasive species in the southeastern U.S. due to its ability to spread rapidly and take over large areas, its high flammability, and the dense mats that are formed which choke out native vegetation.  Control of cogongrass is difficult, as few herbicides are effective, and only at high application rates.  Because of the thickness of cogongrass infestations, pine seedling survival and growth may be negatively impacted.  For more information see www.cogongrass.org

Kudzu: Kudzu (Pueraria montana) is an invasive plant common in the southeastern U.S.  Kudzu can grow several feet per year, and can completely cover trees of all sizes, especially smaller seedlings and saplings.  Similar to cogongrass, kudzu is very difficult to control with herbicides or other methods.  For more information see www.invasivespeciesinfo.gov/plants/kudzu.shtml.

Competing Vegetation: Woody and herbaceous vegetation can have significant negative impacts on southern pine establishment and growth.  Many studies have shown growth reductions in pine when competing vegetation is present.  Therefore, proper pine stand management dictates that competing woody and herbaceous vegetation be controlled during plantation establishment, and competing woody vegetation be controlled as pine stands age.

 

Image citations: Clemson University - USDA Cooperative Extension Slide Series, John W. Schwandt, USDA Forest Service, Mary Ann Hansen, Virginia Polytechnic Institute and State University, Edward L. Barnard, Florida Department of Agriculture and Consumer Services, L.D. Dwinell, USDA Forest Service, Bugwood.org

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