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Habitat

Part 2: The Role of Foreign Plants on Whitetail Habitat

by Dr. James C. Kroll   |  March 8th, 2018 0

In Part 1 of this series, I pointed out some negative impacts of various invasive plants on whitetail forage diversity and quality. Now let’s see what we can do to reduce those impacts.

Foreign-Plants

Kudzu, an aggressive perennial vine from Asia, continues to overwhelm whitetail habitats. Application of Tordon 101 is among the more effective controls. (Photo by LightScribe/iStock)

Some invasives are native to the areas in which they’re causing problems; others have been introduced. Certain native shrubs and herbaceous plants might appear to be beneficial or benign, based on the perception all native plants are useful — but some natives that once occurred in less abundance or only in specific habitats have spread, due to land-management practices.

A RANGE OF CONTROL METHODS
Practical ways in which to control unwanted plants fall into three general categories: mechanical, chemical and prescribed fire. The most expensive are mechanical and chemical, sometimes costing hundreds of dollars to implement.

Foreign-Plants

Roller-chopping can be effective in reducing yaupon, an invasive holly native to the South. (Photo courtesy of Dr. James C. Kroll)

Mechanical treatments include mowing, disking, roller-chopping, chaining and mulching. The equipment used for this type of control can be as simple as a rotary mower pulled by a tractor all the way to specialized equipment equipped with a grinder or mower mounted on the front of the vehicle. These include the “skidsteer”-type machines, hydromulchers and heavy forestry equipment, such as articulated skidders with a grinder mounted up front. Such equipment is powerful enough to take down a tree of significant diameter, but it can cost upwards of $100,000.

Other mechanical treatments involve little more than muscle power: axes, chainsaws, picks and mattocks. As one who grew up intimately familiar with this method, I can say with confidence it’s a time-consuming way to control vegetation. Plus, it’s suitable only for eliminating a few unwanted individuals, not broad-scale habitat work on invasives.

Foreign-Plants

A front-mounted brush cutter such as the EZ Mow from Quick Attach will make short work of many understory invasives.

Chemical control can be quite effective in controlling large areas of unwanted vegetation, but lack of selectivity in many instances can seriously reduce plant community diversity by killing beneficial species along with the bad ones. Some herbicides are designed to kill only specific plant groups, such as grasses, herbaceous plants and shrubs/trees. In order to kill specific species, you often must individually treat each unwanted plant by chemical injection or basal spraying. This of course increases time and cost, but it does allow you to protect beneficial species.

Over my four-plus decades of managing whitetail habitats, I’ve come to rely on a handful of chemicals to control invasives. These include glyphosate (e.g., RoundUp), triclopyr (Remedy), 2,4-Dichlorophenoxyacetic acid (2,4-D), picloram (Tordon) and fluazifop-p-butyl (Fusilade). Each has its unique application method and species control. There are many other herbicides, but I’ve found these to be most useful in managing deer habitats chemically.

There are two drawbacks to chemical treatment. First, many of these herbicides are classified as “restricted use,” requiring an applicator’s license. Even if a herbicide isn’t listed as restricted, I always recommend a landowner or manager acquire the appropriate license and certification for using herbicides. Most state forestry or agricultural agencies offer certification training for individual landowners or commercial applicators.

Lastly, always follow label directions in using herbicides. Improper application method or rate can cause serious damage to deer habitat. A good friend once noted, “My farmer father always measured chemicals in ‘glugs,’ rather than ounces.” That’s the wrong way to do it.

Because many native invasives have spread due to exclusion of wildfire, a properly applied prescribed burn can do wonders in reducing or controlling these plants. Again, the problem is that prescribed burning often requires training or permitting by a state agency. Liability always is an issue in conducting prescribed burns.

SPECIES-SPECIFIC MEASURES
Let’s take a look at what we’ve used successfully to control/manage some of the more common invasives now seen in whitetail habitats. But before starting into those details, let me remind you of a simple truth: You never truly eradicate any pest plant. The best you can do is reduce its abundance and negative impacts.

Kudzu
This aggressive perennial vine was brought to the U.S. to control erosion and provide cattle forage. Viable control measures include mechanical (mowing and removal), heavy cattle grazing and chemical application.

Many herbicides have been tried against this pest, but Tordon 101 has proved to be most effective. I’ve never seen a situation in which prescribed fire could be of any real use for controlling kudzu.

Yaupon
Yaupon holly is a native invasive restricted to much of the South. Exclusion of fire has allowed this species to dominate understory vegetation in pine and hardwood forests. Once established, the plants are so densely packed that prescribed fire is out of the question.

I’ve successfully managed yaupon by using mechanical control,then prescribed fire. Roller-chopping involves pulling a large drum filled with water and armed with sharp blades through the area, using an intermediate-sized bulldozer. This crushes the understory plants but doesn’t kill them, thereby protecting beneficial species. It also encourages the growth of herbaceous plants (weeds and grass), resulting in roughly a one-third browse, one-third grass and one-third weed plant composition. You than can follow with an every-other-year prescribed burn to bring the yaupon under control. Using this method, I’ve been able to triple the productive capacity of forests that had been choked with yaupon.

Japanese Barberry & Exotic Olives
My first exposure to barberry infestations was in upstate New York, where the understory vegetation in many areas is dominated by it. Only under conditions of whitetail overpopulation have I ever seen barberry browsed to any extent. In much of New England, the native understory vegetation has been crowded out by this invasive. When you add in autumn and Russian olive, deer habitat productivity in over 30 states has been negatively affected.

There are three ways to control these species. The cheapest involves using prescribed fire to kill back shrubs; however, if the understory has been overtaken by the invasives, there won’t be enough fuel to even carry a prescribed fire. In such cases, use chemical or mechanical means to knock back the general plant population to allow fuel (grasses and natural litter) to accumulate; then follow with prescribed fire.

Mechanical control in areas not yet dominated by barberry or olive shrubs can be fairly effective. Grubbing out individual plants or cutting them off at ground level can work, though this often requires periodic follow-up removals. If this is followed by prescribed fire at intervals of 3-5 years, you can achieve control.

Chemical treatment of individual plants with triclopyr can be effective, but again requires significant labor. This only works in forests where a few plants have become established. Once a dense canopy develops, use herbicides such as Tordon 101 (picloram plus 2,4-D), applied as a foliar spray not specific to these species.

I’m not providing application rates, as these can be regulated by state agencies. That’s yet another reason for becoming a certified herbicide applicator. It’s best to make herbicide applications either in early spring or late in the growing season, to minimize impacts to native plants. (Note: I’ve not found glyphosate to be effective in controlling barberry or olive.)

Again, prior to using any herbicide, acquire proper permitting or licensing. Also determine whether they’re approved for forestry use in your state or area. Some herbicides are approved for general use; other are restricted to licensed applicators. Always do your homework before using any herbicide — even one sold over the counter at your local farm-and-home center.

These control methods can be effective, but in most cases it will take some time to reduce the pest plant population.So patience is important.

Japanese Honeysuckle
This fast-growing vine has been here so long it’s now widely considered to be “native.” Whitetails love it, and it can be an important browse in late winter and early spring. However, the vines can become overabundant, thus requiring control.

Based on my experience, Japanese honeysuckle is quite susceptible to glyphosate (1.5-2 percent solution) foliar spray. However, mechanical treatment only “makes it mad.” You might spend years trying to eradicate a large patch of Japanese honeysuckle. A combination of prescribed burning and herbicide application is the most effective control measure.

Bush Honeysuckle
Bush honeysuckle is a different breed of cat. Unlike Japanese honeysuckle, this woody shrub isn’t a preferred browse of deer, and it can be very invasive.

Mechanical, burning and chemical control all have been used with success. Spring prescribed burns will kill the seedlings and knock back older plants, requiring repeated burns on a rotation of no more than 3-5 years.

A 20 percent glyphosate solution generally is recommended for chemical control. I’ve also used a mixture of triclopyr and mineral oil or diesel in a 20:80 percent mixture for individual plant treatment during the growing season.

Chinese Privet
This popular landscape plant produces fragrant spring blooms. Unfortunately, it isn’t a desirable deer forage species and can completely dominate the understory.

Control is similar to methods that work for yaupon. However, chemical control often works best, as the plants tend to favor wet lowlands.

You can remove individual privet plants by digging or pulling, but this only works in lightly stocked areas prior to establishment. Mechanical treatment is useful to bring the plants into reach for chemical applications, but this also can result in multi-stem stands of the unwanted plant.

The best herbicides are glyphosate (as a concentrate type product, 41 percent) or triclopyr-diesel (as described above). You can cut shrubs at their bases and then treat the stumps with herbicide, as well.

Juniper
Several species of junipers (“cedar”) can dominate drier whitetail habitats, but the most common ones causing problems are the red berry and blue berry species. Thick stands can reduce deer forage and soil moisture.

Junipers once were restricted to areas where wildfires couldn’t reach them, so obviously prescribed fire can be a useful control agent. It’s been estimated that in Texas alone in excess of 20 million acres have been overtaken by juniper species.

Chaining, dozing, grubbing and root plowing have been used to reduce juniper abundance, followed by prescribe fire after natural fuels build up sufficiently. Foliar spraying with Tordon 22K (1 percent picloram) or soil treatment with Velpar L (hexazonone) around the base of trees has been used. As I discourage use of any soil-active herbicide, I consider Tordon 22K the better of these options.

I’ve had great success in controlling juniper by mulching stands, then using prescribed burning. This is the lowest-cost method you can use.

King Ranch Bluestem
The last invasive species I’ll discuss is one brought to the U.S. as a new cattle forage. It eventually spread throughout Texas and probably has reached Oklahoma. I can think of no other invasive more detrimental to wildlife habitat than “KR.” Once established, it’s very difficult to even control, much less eradicate. The only success I’ve had is a combination of mechanical treatments involving the following steps.

First, mow the plants close to the ground prior to seed head establishment, to prevent reseeding. Then follow with repeated disking to expose the roots of the plants to desiccation (drying). I then repeat these steps for three years. Doing so appears to at least give a foothold to native grasses and other plants. You probably will have to come back periodically and repeat this procedure, however.

I haven’t found chemical treatment to be very useful in controlling King Ranch bluestem, though there recently have been reports of a promising new herbicide (Pastora by DuPont). I can’t yet comment on its efficacy.

Unfortunately, it appears “KR” is here to stay and that it will continue to spread into areas where the climate is conducive to its establishment.

BEST CONTROL OF ALL?
Unfortunately, there are no “magic bullets” for eradicating invasives. They’re here to stay! However, with the methods described here, you should be able to develop an effective plan for controlling invasives on your property. Of course, the single best control measure is not to let them become established on your property to begin with.

The first step in dealing with unwanted plants is learning to recognize them. There are numerous printed field guides and online image banks, so study them to familiarize yourself with what you’re looking for. Then make periodic walks over your property to locate any unwanted species.

Over the last five years, invasive Chinese pistachio (“tallow” tree) has tried to gain a hold at our whitetail research facility in East Texas. However, it’s enjoyed little success. That’s because every spring we walk the property with a shovel and sprayer filled with Remedy:diesel, looking for new seedlings. We also use prescribed burning to deal with this plant. To this point, we’ve had success. However, should we ever stop early control, birds will carry more seeds in their droppings onto the property. It’s a never-ending battle to prevent establishment of invasives.

In short, “the horse is out of the barn” when it comes to these pests. Any sound whitetail habitat management plan includes effective control of invasive plants and ongoing vigilance to make sure they don’t become problems in the future.

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