Introduction

In a southern pine beetle (SPB) infestation, pines most-recently attacked by SPB are often referred to as "fresh attacks." Proper identification of fresh attacks is vital to the success of the verbenone treatment. Identifying fresh attacks is necessary for locating the active head of an infestation. The active head contains the most-recently attacked trees and is the focus of the verbenone treatment. It determines where the buffer of uninfested trees is to be treated. The details of the two verbenone treatments will be discussed further in the online workshop. The procedures for proper identification of the active head are covered below.

Identifying the Active Head

Typically, SPB infestations have a single active head and spread in one direction. However, one must always keep in mind that certain SPB spots can have more than one active head (direction of spread) and can move in any direction. Upon locating the spot, walk around the perimeter and look for infested pines with green crowns (often adjacent to pines with yellow or fading foliage) with one or more of the following signs:

1. Boring Dust - This sign appears before pitch tubes on attacked trees and can be found in the bark crevices, but is often most easily seen caught in spider webs at the base of the tree. Boring dust can vary in color from white to pink to brown. Loblolly pines generally produce more white-colored dust whereas shortleaf pines produces more brown- colored dust. The volume of boring dust should be light to moderate. As other beetles come in after SPB, they produce more dust that accumulates at the base of the tree. Ambrosia beetles produce large amounts of dust (particularly white dust) at the bottom of the tree indicating that the pine is no longer a fresh attack.
   
   
2. Checkered Beetles - An important predator of the SPB is the checkered beetle, Thanasimus dubius. Also refered to as clerids, checkered beetles can be found on the most recently-attacked trees. They are important indicators, because they will often be on attacked trees before boring dust or pitch tubes are detectable. However, checkered beetles are not always present in every infestation in high enough densities to notice their activity. And, like many insects, they may cease activity and take cover if they sense your presence.
   
   
3. Pitch tubes - When trees are not under stress, they will generally respond to SPB attack by producing moderate to copious amounts of resin or pitch which flows out of the bark from the entrance holes produced by attacking beetles. Different species of pine produce different amounts and colors of pitch. Loblolly pine generally produces white or pink color pitch in sufficient amounts to detect from a distance of 10 to 20 ft. Shortleaf pine produces red pitch in small amounts which in some cases requires close inspection to detect. Virginia pine, longleaf pine, and slash pines generally produce the largest amount of pitch in response to bark beetle attack. Pond pine produces copious amounts of red-colored pitch. Pines under stress or suffering from drought may produce no pitch at all. So remember that pitch tubes are not always present. If pitch tubes are yellow in color, hard to the touch and crumble when crushed in the hand, the tree is not a fresh attack. If the tree's foliage is still green, the bark is tightly attached to the tree, and the inner bark remains white, then it may be an unsuccessful attack (i.e. SPB failed to kill the tree), particularly if the pitch tubes are hardened and yellow. Often, pines that were attacked in the fall, although killed by SPB, do not change color until the following Spring. yet.
   
   
4. Egg gallery length and color of sapwood - Use a machette or hatchet to shave the bark just to the surface of the sapwood. It is easiest to find a pitch tube and follow it into the tree. Shaving is necessary because the bark of freshly-attacked pines does not peel away from the sapwood easily. Once you have reached the sapwood, notice its color. If the tree was recently attacked, the sapwood will look white, smooth, and feel moist to the touch, just as you would expect a live tree to appear. Next, follow the gallery to its end, shaving bark as you go. Attacked pines with egg galleries less than 1 inch are considered fresh attacks. If the egg galleries are longer than one inch, or larval galleries are visisble in the phloem layer below the bark, the tree is no longer a fresh attack. If you fail to locate fresh attacks, but other infested trees are present, then infestation growth may have slowed or the infestation may have changed direction. Walk the perimeter of the infestation once again, looking for trees with more recent SPB attacks.
   
   

When a Fresh Attack Isn't

During late fall or early spring, one might come upon a green pine tree with pitch tubes abandoned by SPB brood. Look for exit holes on the bark surface and discolored phloem with SPB galleries to be sure. Keep in mind that SPB enters the tree in cracks between bark plates so if holes are present on the bark surface, they will always be exit holes, i.e. it isn't a fresh attack.

During the Fall

As seasonal temperatures drop, it is common for SPB activity under the bark to remain high while resin flow in the tree itself decreases considerably due to temperature and photoperiod. It is common during November for infested pines to have green foliage yet contain no SPB brood. In these instances, SPB has completed its life cycle and vacated the tree. Some SPB may still remain in the tree to overwinter under or within the bark. Often, exit holes can be found higher up on the bole. Also typical of such trees are pitch tubes that appear fresh at breast height while bark is missing on the upper bole due to foraging by wood peckers. One thing to keep in mind as a general rule is that the progression of SPB development is always one or more steps ahead in the middle of the tree bole than at breast height.

During the Spring

In the northern portions of the SPB range, many trees that were killed during the previous fall may not begin to fade until sap flow resumes and warm temperatures arrive in early spring. In Virginia, for example, green loblolly pines containing brood adults (developed from eggs laid in there) have been observed in early June. During the summer, brood adults usually are found in infested trees with yellow- and orange crowns. Late fading is more common in the northern portion of SPB's range. Also common in winter or early spring is the reinfesting of a tree that was attacked the previous fall. This occurs when a pine attacked in the fall survives through the winter and into spring. First appearances may be confusing because you will see old and new pitch tubes side by side. The old pitch tubes are from the previous fall and the new pitch tubes are most likely from reemerging adults from the same tree attacking a previously uninfested portion of the bole. Although not fresh attacks, a tree of this kind may produce a viable SPB brood that can "restart" the spot once temperatures increase.