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Written by: Matt Nespeca
Invasive Species Consultant
cell: 843-833-5250
Mid-story hardwood control can provide several important advantages
for a forest property, including:
• Increased sunlight for enhanced herbaceous ground cover
and wildlife browse
• Improved aesthetics
• Greater recreational access
• Increased crop tree growth
Mid-story hardwood control can be implemented in pine stands, mixed
pine/hardwood stands and hardwood stands. It is important for a
landowner to assess the value of these types of treatments will
have in reaching their objectives. Not all forests will benefit
from mid-story hardwood control treatments, so it is always important
to know the effects of these treatments before spending resources
and money on the treatment.
Historically, many southeastern forests had periodic natural fire
events occur during the life of a stand, which kept smaller hardwoods
suppressed, leaving the mid-story clear and open, and the understory
lush with native grasses and forbs. Today, prescribed burning continues
to provide a method to maintain a healthy forest. When southern
forests are fire suppressed for several years (or even several rotations),
chemical and mechanical treatments can be excellent methods to get
a forest stand and understory back into shape for wildlife, recreational
and timber management goals.
Mechanical Mid-story Treatments
Mechanical mid-story treatments have become very popular
in recent years. The word “Gyro-Trac®” has become
a common vernacular among forest and wildlife managers. Regardless
of the brand of cutting or mulching machine that is used, mechanical
mid-story control treatments can provide immediate results, and
when used appropriately, they can be an important tool in restoring
a forest area.
Mechanical mid-story treatments are generally conducted by contractors,
and the average private landowner is not likely to purchase their
own equipment to conduct large-scale mid-story control work. Mulching
and cutting machines can clear trees and vegetation in a mid-story
area, and a good contractor can avoid larger crop trees, and even
be species selective in some circumstances. Mechanical mid-story
treatments provide immediate results, but they do not control hardwood
competition. It is a common misconception that mechanical mulching
or mowing reduces the hardwood composition in a mid-story. In general,
a mechanical mid-story treatment will need to be followed by herbicidal
treatments or periodic prescribed burning to reduce the hardwood
rootstock component and release grasses and native forbs. Also,
in heavy mid-story areas, the treatment can add a lot of biomass
to the forest floor, creating a thick layer of mulch and debris,
which will need to break down or be burned off to release the understory
plants.
Herbicide Mid-story Control
Herbicide mid-story hardwood control treatments are generally
implemented after a thinning event, once the hardwoods have sprouted
sufficiently to uptake the herbicide. The greatest impact from herbicide
mid-story treatments can be accomplished when some disturbance has
opened up the stand to sunlight. Herbicide treatments provide us
with a tool to select the kind of plants that are going to recolonize
a site. Herbicide mid-story hardwood control is valuable across
the range of management objectives, from intensive timber management
to quail management, but the treatment selectivity will vary depending
on the desired plant composition outcome.
Herbicide selectivity can be accomplished by many different methods.
I will provide examples of different ways that a landowner may use
herbicides to alter the plant recolonization in a forest stand.
Due to the variable situations that landowners are faced with, I
will not discuss specific product rates. In any case, it is important
to get on site advice from an expert, and always read herbicide
labels and instructions before initiating any herbicide treatment.
Selectivity due to herbicide spectrum
Every herbicide has a spectrum of plants that it controls
well, and plants that it does not control well. A landowner can
use a broadcast herbicide treatment to control undesirable vegetation,
while releasing desirable plants. The herbicide rate or concentration
can also have a significant effect the spectrum of control from
a treatment.
Example 1 (pictures to the right): Arsenal®
AC herbicide controls hardwoods like sweetgum, maple and yellow
poplar very well, but Arsenal AC does not control blackberry, legumes
or southern yellow pines. For a mid-story treatment in a loblolly
stand, a treatment can be made with Arsenal AC by ground or over-the-top
by helicopter that will control undesirable hardwoods, and release
blackberry brambles or legumes.
Example 2: Forestry Garlon® XRT herbicide can reduce hardwood
resprouts, but does not control grasses. In a thinned pine or hardwood
stand, a treatment can be made with Forestry Garlon XRT by ground
that will reduce the hardwood component of the understory, while
releasing grasses and allowing for recolonization by native forbs.
Example 3: Velpar® ULW is extremely effective at controlling
oak competition on sites with sandy soils, but does not control
many native grasses like wiregrass and indiangrass, or shrubs like
blueberry. In a thinned longleaf pine stand, a treatment can be
made with Velpar ULW by ground or over-the-top by helicopter that
will control oaks, while releasing the longleaf pine, native grasses
and shrubs.
Selectivity due to herbicide placement
Even broad spectrum herbicides can be used selectively by directing
your treatment only to hardwoods or plants that you want to control.
Example 1: In a quail savannah that has excellent native grasses
and forbs in place, Arsenal AC can be applied to the foliage of
sweetgum and other undesirable hardwoods through a directed spray
backpack treatment.
Example 2: In a bottomland hardwood area, Chinese tallow or other
undesirable trees can be controlled by individual stem hack-and-squirt
treatments using products like Arsenal AC, Milestone® VM Plus,
and Accord® XRT II.
Selectivity due to timing
Certain foliar active herbicides can be used in a forest
stand during seasons when desirable species are dormant, but undesirable
hardwoods are susceptible to the herbicide treatment.
Example 1. In a bottomland hardwood stand with a heavy infestation
of Chinese privet, a broadcast treatment of Accord XRT II can be
used in winter to control the privet infestation, while maintaining
safety for desirable hardwood regeneration and crop trees.
Example 2: Even though longleaf is a sensitive species, over-the-top
treatments of Arsenal AC can be used in fall on young longleaf stands
to control undesirable hardwoods while maintaining safety for your
longleaf.
About the author: CWC Chemical employs Matt Nespeca
as an invasive species consultant. Matt has 12 years of experience
in vegetation management, and has worked extensively with complex
invasive plant problems throughout the southeast. He worked for
7 years for BASF Corporation as a technical specialist, sales representative
and product manager. Matt has a M.S. in Forest Biology from Virginia
Tech, and a B.S. in Forest Resource Management from Auburn University.
Matt is both a registered forester and commercial applicator, and
partners with a network of specialized applicators and professionals
to provide results for landowners, land managers and other clients.
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