Several herbicides are well suited for use in weed and brush control
in natural areas. The herbicides discussed here have been carefully
established to be safe and effective if used properly. Before using
any herbicide, it is essential that the label be read completely
and its specifications followed.
Purpose and Need
Herbicides are used to facilitate restoration in prairie and savanna
ecosystems in conjunction with other methods, including hand pulling,
mowing, cutting, prescribed burning, seeding, and cultivation. Herbicides
should be used as part of an integrated weed management strategy.
The precise treatment method used will depend upon the target species,
its life history, the extent of the problem, and the compatibility
of the herbicide with the restoration objectives.
Why use Herbicides?
Invasive plants are a threat to management and restoration of natural
ecosystems. In many areas, due to neglect over many years, existing
native vegetation has become heavily infested with invasive species.
Most of these invasive species are nonnative, having been introduced
from Europe, Asia, or other distant places. Examples of exotic species
include sweet clover, wild parsnip, reed canary grass, purple loosestrife,
garlic mustard, honeysuckle, buckthorn, and Kentucky bluegrass. The picture to the right is of buckthorn that was cut but not treated with an herbicide.
Some native plants are unusually invasive and may also be a threat
to ecosystem function. Examples of native invasive plants include
smooth sumac, gray dogwood, hawthorn, sandbar willow, and prickly
Invasive plants compete with desired species for light, nutrients,
and moisture. They may alter hydrological regimes in wetlands, or
alter the structure of upland plant communities. Although invasive plants can be removed without the use of herbicides, in many cases the cost is prohibitive. In some situations, herbicide use is essential.
Only Non-Aquatic Habitats Discussed Here
The discussion here deals only with non-aquatic habitats. Some
herbicides are approved for use in aquatic habitats, but the kinds,
uses, and requirements are different.
Spot Spraying and Broadcast Spraying
For most herbicide applications in natural areas, spot spraying
is preferred. This permits application of the chemical just to target
species. Foliar application should be made with a low-pressure (20-50
psi) backpack sprayer equipped with a wand applicator. A sprayer
nozzle which creates a flat or cone-shaped pattern is preferable.
The herbicide should be allowed to dry for at least two hours to
ensure adequate absorption. (Do not spray when rainfall is threatened.)
Addition of a nonionic surfactant to the mixture helps ensure complete
leaf coverage and increases the rate of absorption. The herbicide
should thoroughly cover the foliage but not to the point of run-off.
Personnel applying herbicide must be properly trained and knowledgeable
about the native vegetation.
Broadcast spraying in natural area restoration is used primarily
when a fallow field is to be planted to prairie. It must be ascertained
first that all of the existing vegetation is undesirable. The field
can then be treated with a nonspecific herbicide such as glyphosate,
which kills all existing vegetation. A boom sprayer towed behind
a tractor is usually used.