Prescribed fire is a commonly used management tool in both pine and hardwood forests in South Carolina. When used correctly, it has many benefits to forest ecosystems. Fire helps reduce fuels on the forest floor, which can help lower the chances of a wildfire. It helps recycle nutrients, making them more available to the growing vegetation, and it helps reduce woody competition, resulting in increased growth to crop trees.
Prescribed fire has many benefits for insect, fungal, and invasive plant pest control as well. While few insects are directly controlled by fire, some may be killed by the flames and heat if the fire occurs when the insects are present. In pines, prescribed fire does not usually result in a great deal of pine bark beetle mortality, but fire does kill competing vegetation. Since pine forests with a lower basal area and less woody competition are less susceptible to pine bark beetles (like the southern pine beetle), prescribed fire indirectly contributes to forest health by increasing the resistance of burned stands to pine bark beetles. However, fires that burn too hot can injure and scorch trees, which may make them more susceptible to turpentine beetles and Ips bark beetles. All in all, the application of prescribed fire as a management tool is part science, part art, and part experience, as many factors contribute to a fire’s effectiveness.
Prescribed fire can also be an effective management tactic for some fungi. Brown spot needle blight, a fungal disease that often impacts young longleaf pine stands, is easily controlled by prescribed fire. This fungus causes needle loss primarily in grass stage longleaf. The fungal inoculum persists on the dropped needles under the tree. These needles act as a constant source of fungal infection, and spores reinfect the living needles by wind or rain splash. By burning the pine stand, the shed needles and fungal inoculum are destroyed, and the disease is usually controlled without the use of pesticides. This strategy also works on many fungal pests that attack hardwood foliage. Fungi like tar spot of maple and Tubakia leaf spot of oak overwinter on fallen leaves – burning these during the dormant season can help reduce the next spring’s chance of infection.
While prescribed fire can be an effective management tactic for many native insects and fungi, invasive species are usually not impacted. Invasive insects like the emerald ash borer (which kills ash and is present in the Upstate), the Asian longhorned beetle (which kills maple in the Lowcountry), or the redbay ambrosia beetle and laurel wilt fungus (which kills trees in the family Lauraceae, like bay trees or sassafras, across much of the state) are generally not impacted by prescribed fire. These pests are also not impacted by forest management in general, as the pests attack healthy, living trees.
Using prescribed fire to control unwanted vegetation often has mixed results, depending on the species targeted and the timing of your burn. Growing season burns are more difficult to implement but often result in greater woody stem mortality. In contrast, dormant season burns are easier to conduct but may not give the same amount of vegetative kill as growing season burns. Invasive grasses, such as cogongrass or Japanese stiltgrass, tend to respond positively to burns. While burns may kill the aboveground vegetation, increased sprouting or germination from the seed bank often results.
For woody vegetation – especially shrubs – prescribed fire often top-kills larger stems, resulting in multiple resprouts after the burn. For example, Callery pear can send up anywhere from 2-12 resprouts for each stem killed by fire. For this reason, prescribed fire should not be seen as a silver bullet for invasive plant management, but it can be an effective component of your management plan. After the plants resprout and grow to about 2 feet tall, herbicide can effectively kill the unwanted vegetation. Prescribed fire may kill shrub or tree seedlings and even the seeds of some invasive plants, but once woody plants develop thick or corky bark, prescribed fire is unlikely to have much of an impact.
In most cases, prescribed fire can and should be used as part of a forest management plan. When used correctly, you will positively benefit from using prescribed fire as a form of pest management in your pine and hardwood forests. Contact your local Clemson Extension County Agent if you have questions about your specific forest management situation.
Dave Coyle, Cooperative Extension, Forestry and Wildlife Specialist
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