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6 Discussion and Conclusions

Table 1 and Table 2 summarize the current status of, current prevention and control strategies for, and likely changes in the amounts of damage that will be sustained from each of 21 forest pests in Southern forests. We make no strong claims about the accuracy of these projections and provide them only as a useful summary.

Questions we have attempted to address concerning the health of the southern forests include:

- Are the effects of insect pests and diseases affected by forest type?

- What are the likely effects of large acreages of single-species plantations?

- What effect does intensive management have on insect and disease incidence?

- How will pest impacts differ among the major classes of land ownership?

- Will problems with non-native insect and disease pests continue to increase?

Each of the pests discussed attacks a particular host or group of host species. Several of the pests discussed have the potential to eliminate their host species from the ecosystems in which they currently thrive.

Single-species planting, often called monoculture, is an economical way to produce wood or fiber of desired species rapidly. However, the concentration of single-species plantings over large areas offers great opportunities for forest pests that normally attack only the planted species or a small group of species which includes it. It seems obvious that populations of the pests that attack pine can expand and prosper in a pine monoculture. The fusiform rust fungus may be the outstanding example of a relatively minor pest becoming a major one because of plantation forestry.

Intensive forest management is a mixed blessing from the standpoint of pest management. While it is most commonly practiced in single-species plantations, and runs the risk of catastrophic losses to insects and diseases, it also offers great opportunities to minimize pest impacts. One of the primary objectives of intensive management is to keep individual trees vigorous, and such trees usually are less susceptible to pest damage than their slow-growing counterparts in unmanaged, less-thrifty stands. In intensively managed stands it usually is practical to salvage trees that have been attacked by forest pests. In addition, healthy, intensively managed stands generally recover more quickly following a pest attack.

Risks of major losses to pests vary considerably by class of owner. Increasingly trees on public land are being grown in long rotations and in natural stands rather than plantations. Natural stands with mixed species composition have somewhat less risk of suffering catastrophic loss to forest pests. But susceptibility of individual trees increases as the trees age. Oak decline, for example, is taking a huge toll of aging oaks on public land.

When pest problems appear on industrial tracts, they are generally identified and dealt with promptly.

The same usually cannot be said for nonindustrial private land; the great diversity of owner objectives and management styles results in a variety of responses to pest problems. Most of the owners have little knowledge about pest problems and solutions, and many of their stands are not intensively managed. Commonly they are not even thinned before tree vigor starts to decline. In addition, desirable treatments often are not practical on the small tracts held by nonindustrial private landowners.

The greatest threat to the future health of southern forests is the introduction and spread of non-native invasive pests. Once these pests are established, a lack of natural controls permits them to become extremely destructive and almost impossible to eliminate. Regulating the movement of plants and plant materials, and detecting and eradicating new pest introductions, are responsibilities of the USDA Animal and Plant Health Inspection Service (APHIS). The USDA Forest Service and State forestry organizations work closely with APHIS to prevent introductions and to eradicate them where they occur. Nevertheless, introductions continue to occur, and eradication efforts often fail. The problem is not unique to the South or to the United States. It is an international problem of major proportions.

Among significant non-native pests established in the South are the hemlock woolly adelgid, beech bark disease, dogwood anthracnose, the European gypsy moth, and the Formosan termite. Pests that are likely to be introduced include the Asian long-horned beetle, the pink hibiscus mealybug, and the Asian gypsy moth. Monitoring and suppression will continue to be important tools for preventing and managing these pests.

Risk assessment is one of the most important aspects of forest pest management. If the risk of a major loss is low, there is little point in spending a lot of money and disturbing environments to control a pest infestation. The USDA Forest Service has begun to evaluate areas at high risk from several pests. Areas are considered to be at risk if tree mortality of 25 percent or more is expected during the next 15 years. Nationwide, some 59 million acres of forest are thought to be at risk from insects and disease-causing agents. Gypsy moths and southern pine beetles are the leading causes of risk in southern forests. Some 15 million southern acres are rated as high risk because of these insects (Figure 17).

The Forest Health Monitoring Program was established in 1990 to assess and report on the health of the Nation's forest ecosystems. It is a cooperative multi-agency effort. The Program provides for: (1) establishment of permanent plots throughout the Nation; (2) performance of aerial and ground surveys; (3) analysis of plot-based data from USDA Forest Service Forest Inventory and Analysis Units, national forest inventories, and forest health protection inventories; and, (4) development of necessary methods to achieve assigned tasks.

Monitoring data support the conclusion that 85 to 90 percent of the trees in the South are healthy. These data also show that there are major concerns for the health of the forests in some areas (caused by oak decline, beech bark disease, and others), and also for some individual species of forest tree (eastern and Carolina hemlock, dogwood growing in specific conditions, and others).

Practical control methods for many pests are still lacking. Problems with treatment delivery, biology, public acceptance, economic practicality, adverse impact on non-target species, and many other obstacles affect development and deployment. The use of chemical pesticides in Federal forestry has declined due to the difficulty of procuring and maintaining EPA registration of products and also due to public pressure. Replacement silvicultural, genetic or biological strategies are often unavailable. Fragmentation of nonindustrial private ownerships makes it more difficult to implement control procedures there. Continued use of synthetic chemical pesticides will be necessary for the near future to keep pest problems manageable until alternative strategies become available.

Integrated pest management (IPM), the concurrent or consecutive use of a variety of tools or practices to control pests, is the overall process preferred by State and Federal agencies. Developing and implementing IPM for a particular pest is a complex process that requires considerable research. A systems model of IPM developed by Waters and Ewing (1974) (Figure 18) indicates the complexity of developing an IPM system for the southern pine beetle.