Fusiform rust is caused by the fungus Cronartium fusiforme and is widely distributed throughout the south. This disease is especially damaging in slash pine plantations and to a lesser degree in loblolly by forming a resinous gall or canker near the point of infection. This canker reduces growth and weakens the stem until breakage occurs because of wind or even the tree’s own weight. Mortality is highest among slash plantations that are less than 10 years old. The USDA Forest Service estimates annual stumpage losses in the neighborhood of $28 million.
Cronartium fusiforme requires alternating hosts throughout its life-cycle. This fungus spends part of its life in pine tissue and another part on oak leaves. The galls on pine trees produce spores from February to April that are carried to oak leaves on the wind. Once the oak leaves are infected, the spores reproduce and germinate. After a few weeks, the new spores are carried to new pine hosts on air currents. If these spores find their way to a susceptible host, the fungus begins growing in the living tissue of the pine and results in a gall the following spring.
Fusiform rust is controlled on a small scale in nurseries through the use of fungicides ,however; this method of control is not economically feasible in pine plantations. Reforestation planning should take into consideration the risk of an establishment site being infected, based on the history of the site and the surrounding area. Sites that are determined to be of high risk should choose loblolly, which is more resistant than slash pine. Additionally, newer generation varieties of slash and loblolly should be selected when available because of their increased resistance to fusiform rust.
Once a stand has been affected by this disease, it is extremely important to have it correctly thinned when it becomes merchantable. Plantations with a high occurrence of fusiform rust should always be marked by a forester ahead of a thinning by a forester. This ensures that every tree in the stand is checked for the disease and if found, removed. Thinning operations that rely on the cutter operator to select take-out trees never result in complete removal of this disease and other deformities.
Pine Bark Beetles
Pine bark beetles attack our forests and stands of trees, which are stressed or appear to the beetles to be stressed. Mother Nature naturally thins our forest in many ways: wind, fire, flood, drought, insects (bark beetles) etc... In nature when trees begin to compete with each other for sunlight, water, and nutrients the trees become stressed and begin to die off. When the weak trees in a stand become stressed and begin to die, they emit an odor to which bark beetles key on and are attracted. Bark beetles flock to the unhealthy stand, and begin their relentless attack on the stressed and dying trees. Once the assault begins, many times healthy as well as unhealthy trees are attacked.
Southern Pine Beetle
Ips Engraver Beetle
Black Turpentine Beetle
Southern Pine Beetle (SPB) is the most destructive of the three types. There may be up to six generations of beetles per year. Adult SPB bore directly into the bark and mate. The females excavate the characteristic S-shaped egg galleries in the inner bark. Adults and larvae alike girdle trees quickly as they completely encircle the tree. The tree’s death is hastened by the introduction of blue-stain fungi which blocks the flow of nutrients and water to the crown of the tree. The pattern of movement is a key indicator when identifying this beetle. Their movement across entire stands in short periods of time is what makes this beetle so devastating.
Ips Beetles are very similar in nature to Southern Pine Beetles. The adults and larvae completely girdle/encircle the inner bark of the trees, and with the aid of blue-stain fungi cut off the continued supply of nutrients and water, trees need for survival. Most of the time Ips beetles attack trees individually or in small groups, searching for weak trees throughout the stand. They move from one spot to another (this movement is an identifying characteristic pattern), but under favorable conditions can become epidemic and can devastate a stand.
Black Turpentine Beetles are the largest major bark beetle in our southern forests. These beetles create characteristically large pitch tubes which extend no higher than eight feet above the ground. There are usually only two full generations per year. This beetle does introduce blue-stained fungi into the tree. The larvae feed in patches instead of completely girdling the inner bark of the tree, like Ips and Southern Pine Beetles. If the beetles are identified early, they can be treated with a chemical and in many cases the trees can be saved.
Nantucket Pine Tip Moth
Nantucket pine tip moths are common in forests throughout the eastern US. Of the pine species we manage, loblolly is the most susceptible after five years of age, but all pine species may be attacked in the seedling stage up to five years old. Pine tip moth damage almost certainly occurs in every plantation because of this insect’s abundance, but it’s when a stand becomes infested at a young age that this forest pest can really affect the long term performance of a timber stand. Loss of growth and tree deformation are caused by this pest’s attack, which translates into loss of revenue at harvest time.
Infestations of pine tip moth are often controlled by naturally occurring biological means such as fungal pathogens, predatory insects, and egg parasites. This helps to keep the pine tip moth’s numbers in check. Unfortunately, certain climate conditions occur periodically that suppress these biological agents’ ability to impact pine tip moths' numbers. During these years, moth populations can explode and it may be necessary to control these pests with an aerial applied insecticide.
It is important to keep check on newly established pine plantations in order to monitor pine tip moth activity. Seedling survival monitoring and periodic checks done by our foresters allow them to recognize any stand health issues that may arise from pine tip moths and other forest pests.