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FIRE FACTS: What is needlecast? And why is it a problem for firefighters?

September 2, 2023
News article

When fire-stressed evergreens shed dry needles after a wildfire, they raise the risk of another blaze

When pine trees and other evergreens are damaged by the smoke and heat during a wildfire, but not actually consumed by the fire, after a period of time the dead needles will start falling out of the trees. This is generally referred to as “needlecast.” for wildland firefighters, it includes any dead, dry leaves falling from trees and brush in the fire area.

Typically, needlecast will start to occur about 2 weeks after the fire burned through an area. However, the extended drought in southern Louisiana already stressed trees and vegetation before fire affected them and appears to be a contributor to earlier start of “needlecast.”

Forested areas with many pine trees like here in southern Louisiana, always present a special challenge. Wildland firefighters know that when needlecast starts, that means there is a new layer of unburned very dry fuel falling from the trees to build up on the ground. These new fuels are highly receptive to ignition from any hidden heat source and will result in new fire starts within the burn area.

So, what can firefighters do about “needlecast”?

  • Once a fireline is placed around a fire, wildland firefighters must remove all heat sources from the edge of the fireline by using hand tools and, where available, water, to eliminate embers and heat at least 100 feet from the fireline. This is referred to as “mop-up.” It's very labor intensive, and is absolutely essential to prevent “re-burn” from needlecast or other sources of fuels.

  • Firefighters must also constantly patrol the firelines to keep them clear of accumulated needles and other dead and falling vegetation. The needle layer is capable of carrying fire over the fireline and must be dealt with to prevent that from happening, particularly on windy days. Usually we remove needlecast from the line by raking or with a leaf blower.

Fire stressed trees that lose their needles or leaves are not necessarily dead. After sufficient rain events, many trees that appear to have died in the fire will resprout new needles or leaves in time.