Attacks by Southern Pine Beetles
Loblolly is one of the most challenging trees to treat because it grows so prolifically, thick, and in such dense old growths that it is hard to get into the heart of a forest to treat the interior trees.
The Southern Pine Beetle (Dendroctonus frontalis) infests and kills Loblolly pines throughout most of its range in Southern and Eastern United States from middle Texas East across the deep south, up and through Kentucky, West Virginia, the Carolinas and down through Florida. It will also infest shortleaf pine (Pinus echinata Mill.), pond pine (P. serotina Michx.), and Virginia pine (P. virginiana Mill.) (Thatcher and Barry 1982).
A new report states, "New Jersey’s trees are (also) in trouble. Southern Pine Beetle, a bark beetle smaller than a grain of rice, killed pines across the state’s southern forests. In 2010 alone, the beetle destroyed 14,000 acres and continues to spread." It has now moved even further North.
Southern Pine Beetles generally have a short life cycle, making suppressing them difficult - especially in the southern-most states. They start to fly very early in the spring (correlated with the flowering of the Dogwood tree in Florida). In the Gulf Coast region, what we know about the reproductive potential and seasonal habits of the SPB clearly suggests that, to reduce beetle populations, direct control should be applied during the winter to be in place and ready when they reach peak flight in late winter and early Spring.
Verbenone Application dates will vary with latitude and climate but are typically started before the ambient average temperature consistently exceeds 80° F.
In the Coastal South where temperatures are mild, flights recur several times, and re-treatment is required. Spots may remain active throughout the year. SPB can emerge and attack in Dec, Jan, and February in large part undetected because new infestations in the Gulf Coast Regions during the fall, winter, and early Spring are difficult to detect due to inclement weather or wet ground conditions. Consequently, as many as 3-4 consecutive beetle generations may effectively escape control during the very season when the attack:emergence ratio of the insect is at its highest.
SPB attacks certainly begin by early spring and can occur well into autumn; as many as eight generations can occur in one season. Each successive generation attacks nearby live trees. As a result beetle attack resembles an advancing front, much like an army on the attack.
Control during the winter is less problematic in the northern part of the beetle’s range (Tennessee, the Carolinas, Virginia and north). Cold winters tend to restrict beetles to the multiple-tree spots they occupied during the fall; this fact simplifies winter detection. Since the beetles complete only three to five generations per year in this area, overwintering broods seldom emerge before late April or May.
Newly hatched adults leave the tree of their metamorphosis, seeking out larger trees in the surrounding area.
When the adults arrive at their tree of choice, they begin tunnelling under the bark. Soon after initial attack, females emit an aggregation pheromone (frontalin), which attracts males and more females to the tree. This pheromone, in conjunction with host odors stemming from resin exudation at attack points, attracts more SPB to the tree.
Resin under pressure within the tree can successfully force out or "pitch out" beetles if there are only a few beetles and the tree is relatively healthy. (see Pitch Tubes in the image left) However, mass-attacking SPB deplete the resin production capabilities of the tree causing resin flow to cease, after which point the tree is easily overcome.
Females lay fertilized eggs. The bad news is that Parent adults may then re-emerge from the tree one to 20 days following depositing the eggs and proceed to attack the same tree or another (Thatcher et al. 1980). The original eggs, which turn to larvae, develop to produce more egg-laying adults to attack more trees. Additionally, the hatched larvae feed under the bark in the phloem layer, introducing fungi, yeasts, and other organisms that lead to tree death. see See this entomology report from the University of Florida
The Southern Pine Beetle presents more challenge than Mountain Pine beetles or Fir Beetles due to its general geographic location in milder southern climates. SPB attacks begin in early spring or late winter and can occur well into autumn; as many as eight generations can occur in one season making the beetle attack resemble an advancing front, much like an army on the attack. Prophylactic treatments (such as Verbenone) must be used IN FRONT of the "spear" of the attack.
Spots may remain active throughout the year in the lower Gulf Coast. Each successive generation attacks nearby live trees. It is estimated that one infested tree will kill at least two and possibly more trees, and each generation adds to the mortality. Thus the exponential devastation occurs.
Quick Guide to Signs of Southern Pine Beetle Attack
As always, the best defence against Southern Pine Beetle is a healthy stand of trees that are able to defend against attack. Proper spacing, basal area, water and removal of brood trees and unhealthy trees are all important.
It is also important to remove and properly dispose of infested trees and slash prior to trying to deter beetle populations from attacking good trees in the stand.
Dense stands of large Loblolly trees are at highest risk of attack There has been some research into direct control using the anti-aggregation pheromone Verbenone, which disrupts beetle aggregation in Mountain Pine Beetles. According to the USDA Forest Service, Southern Research Station, in Louisiana, "disruptant semiochemicals, primarily verbenone, have shown some promise for spot disruption, but they are not used operationally".
If using Verbenone to suppress SPB attack, it seems to be of importance to treat the trees that are on the forefront of the attack (the leading spear that points the direction the infestatino is moving), making a concetrated effort to protect an area IN FRONT of the direction of movement. (Salvage and burning of infested trees is also of paramount importance for reducing tree mortality.)
It is not the actual Pine Beetle that kills your tree. The Beetle vectors several pathogenic fungi which facilitate successful colonization and tree mortality. There are no survivors from a successful attack. When a beetle-attacked tree is cut down, you can usually see the blue stain fungus that has colonized the tree (introduced by the beetle). It is the fungus that kills the tree. As there is no cure for the fungi, we must deter the beetles.
Beetles and other insects communicate using pheromones. Verbenone - a synthetic pheromone - replicates the beetle pheromone of the Mountain Pine Beetle, sending a message that the tree is full and that the food supply is insufficient for additional beetles. Arriving beetles receive the "message" that they should look elsewhere for a suitable host.
Verbenone helps control:
And can be used on:
Verbenone for Mountain Pine Beetles has been used as part of integrated pest management programs (IPM) for more than a decade against that beetle. Many studies show that areas treated with Verbenone, as part of an IPM program, fare significantly better than those that are not. Verbenone use for Southern Pine Beetles is less-researched. Research in the 1990's posited that it takes considerably more concentration of verbenone to achieve effect. Others felt that it does not work at all. The University of Florida states, "Much research continues toward the development of effective methods of utilizing semiochemicals to suppress SPB infestations, but as yet, operational uses are still on the horizon." No "surefire" product is in the marketplace at this time.
Verbenone is environmentally safe and non-toxic to humans, pets, birds, and even the beetles themselves. Registered by EPA and most Rocky Mountain States. All pheromones in controlled release dispensers are approved organic by USDA/NOP. It is user and Eco-Friendly. Unlike the insecticides approved for Pine Beetle control,Verbenone does not kill bees, beneficial insects, aquatic organisms. Not restricted use. Always follow label instructions.
There has been some research into direct control of SPB using the anti-aggregation pheromone Verbenone, which disrupts beetle aggregation in Mountain Pine Beetles. According to the USDA Forest Service, Southern Research Station, in Louisiana, "disruptant semiochemicals, primarily verbenone, have shown some promise for spot disruption, but they are not used operationally".
If using Verbenone to suppress SPB attack, it seems to be of importance to treat the trees that are on the forefront of the attack (the leading spear that points the direction the infestation is moving), making a concentrated effort to protect an area IN FRONT of the direction of movement. While an area of red trees shows the "spot" that is infested, the trees that are most recently infested (yellow) are on the front of the attack. Trees immediately in front of the "yellow spear tip" should be treated as a barrier to further advance.
Of course, as stated earlier, salvage and burning of infested trees is also of paramount importance for reducing tree mortality.
Generally speaking, in most Gulf Coast states, treatment should begin in October, again in February, and again in June to last through October.
Verbenone is prescribed as part of a multi-faceted approach to pine beetle management. No single treatment can totally prevent attacks. Additionally, preventative measures will need to be repeated as often as the life cycle of the particular beetle in the particular habitat you are treating.
Please talk with your local forest service or department of agriculture before embarking on a program of Verbenone to repel SPB.
Studies have shown that during epidemic conditions, the pressure from beetle populations who must go somewhere (even if conditions are not optimum for them) may reduce the effectiveness of all treatments. Given the "find a tree of any size or perish" imperative that emerging pine beetles face, they may habituate to both chemicals and pheromones. However, we still have a few years to work on the problem in areas that are not yet overrun. That time may give just the breather necessary to let nature begin to draw back the danger or for other management techniques to take hold.
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