Cut and Leave:
A Method for Controlling Southern Pine Beetle Infestations

Forest insect and disease pests cause an estimated growth loss and mortality in excess of $8 million each year in South Carolina forests. An integrated pest management (IPM) approach on your forest lands could significantly minimize your potential losses.

The Southern Pine Beetle

The Southern Pine Beetle (SPB) is the most destructive pine bark beetle in the South. SPB infestations commonly originate in poorly managed or overstocked stands. Once underway, outbreaks can spread rapidly, killing trees  over hundreds of acres, and move into managed stands.

SPB infestations can be identified in several ways. The most obvious symptom is the change of the needles in the tree crown from green to yellowish to reddish brown. Other symptoms are listed in Table 1.

Initial infestation is followed by the development of a "spot." The spot usually spreads in one direction as new trees are attacked in an area called the "active head" (see Figure 1). For more information on identification and life cycle of the SPB,, see Forestry Leaflet No. 5, Identification of the Southern Pine Beetle.

The risk of SPB infestations can be reduced by practicing proper forest management. However, when infestations (spots) do occur, direct control tactics are needed to minimize timber losses.

Cut-and-Leave

The cut-and-leave method is an effective means of controlling small remote spots (10 to 50 infested trees) that cannot be salvaged. The method involves felling infested trees and leaving them in the forest. The treatment disrupts spot growth and disperses the emerging adult beetles. Spots should be treated only if they contain freshly attacked trees.

When to Apply Cut-and-Leave

Cut-and-leave should be used during the period when SPB spots are expanding (approximately May to October). This method is most effective on spots of 10 to 50 active trees. Spots with fewer than 10 infested trees usually do not need to be treated. On the other hand, spots with more than 50 infested trees can be treated using cut-and-leave if the trees will eventually be salvaged. In every case, prompt treatment after detection is recommended.

How to Apply Cut-and-Leave

1. Select spots with 10 to 50 infested trees. Some must have fresh attacks. Spots with a high proportion of freshly attacked trees should be treated first.
2. Mark and fell all actively infested trees toward the center of the spot (see Figure 2).
3. Mark and fell a horseshoe-shaped buffer strip of green uninfested trees around the active head of the spot. Fell them toward the center of the spot and leave them on the ground. In small spots the buffer may encircle the entire spot. However, the buffer should be no wider than the average height of the trees in the spot. The buffer is necessary to ensure that no freshly attacked trees are left standing.
4. Dead trees with no bark beetles remaining should be left standing. Beetle parasites and predators complete their development in these trees and emerge to help control beetle populations. The trees also serve as den sites for certain woodpecker species.
   
5. After two weeks, check the treated spot for reinfestations (breakouts) around the edges of the spot. Treat breakouts as needed.

Advantages and Disadvantages

Cut-and-leave is practical, relatively inexpensive, and requires a minimum of manpower and equipment. The treatment can be applied soon after spots are detected, even when salvage crews are not available or in areas not readily accessible to salvage equipment.

The main disadvantage is that a buffer strip of green, uninfested trees must be felled and left around each spot to assure that all newly attacked trees are included in the treatment. However, if salvage becomes feasible at a later date, all felled trees can be removed and utilized.

Glossary of Terms

• ACTIVE HEAD(S) OF SPOT - Area(s) of the spot containing beetles in the process of attacking green pines.

• INFESTED TREE - A pine containing southern pine beetle broods (eggs, larvae, or pupae) or attacking adults.

• BUFFER STRIP - A group of green, uninfested pines that are cut adjacent to the most recently infested trees in the spot.

• SPOT - A group of dead or dying pine trees infested by the southern pine beetle.

• SPOT BREAKOUT - An infestation of green pines on the outer edge of a spot following a control treatment.

• SPOT GROWTH - The natural expansion of untreated spots as additional green pines become infested in the active head of a spot.
• SOUTHERN PINE BEETLE - A small, dark brown beetle that can be identified by the S-shaped galleries or tunnels that it makes under the bark of attacked trees.

Additional Information

Keeping your pine timber stands healthy and vigorous, and having a good knowledge of the southern pine beetle habits and symptoms is essential to effectively deal with this destructive pest. Professional advice and assistance is available through the South Carolina Forestry Commission, Clemson University Cooperative Extension Service, U.S.D.A. Forest Service, forest industry personnel, and private consulting foresters.

Department of Forest Resources