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Low-cost weed-control strategies that work wonders.
Graziers around the country agree: Sound grazing management can go along
way toward forcing noxious weeds out of pastures, making more room for
productive grasses and legumes. But with some weeds, that may not be enough.
Judging from discussions on the graze-l internet listserver, thistles top of the
list of persistent problem weeds that require vigilance, persistence and a few
tricks to rein in. Fortunately, early fall is one of the best times to tame
thistles. So you still have a chance this season to take some of the sting out
of these unwelcome invaders, and have cleaner pastures next year.
are at their worst in mismanaged or newly established pastures. "Thistles
and burdocks have been a common problem wherever I've worked developing new
pastures or improving old, overgrazed ones," observes Tom Cadwallader, a
University of Wisconsin Extension Livestock Agent based in Merrill, Wis. "I've
used clipping, shovels, and a variety of herbicides," he adds. "Regular
spot treatment with any of these will cut off the majority of growth during the
first couple of years -- if the pasture is being managed to promote strong
competitive grass and legume growth."
Here are some key
strategies to consider:
Know your opponent.
Canada thistle is the toughest member of the family. This perennial multiplies
both by seed and spreading horizontal roots called rhizomes. Most other
thistles, such as bull and musk thistles, are biennials. Their first year, they
produce 4- to 18-inch-wide rosettes, but must first go through a cold winter
period before they flower, set seed and die the following season. Unlike
Canada thistle, these biennials can be knocked out by keeping them from setting
seed. On suitable ground, rotating to annual crops for a year or two will
usually wipe them out because they can't take the combination of tillage and
Use an ounce of
prevention. Thistles are opportunists, just waiting for a chance to sneak
into open spots in your pasture sward. So keep your sod thick and healthy by
not overgrazing and ensuring adequate fertility and lime, and you can shut out
thistles before they get a foothold.
"I can't emphasize enough that the best weed control -- including
for thistles -- is a dense, vigorous, rapidly growing perennial sod that fully
covers the soil," stresses Dr. Ann Clark, a grazier and agronomist at the
University of Guelph in Ontario. "I do not doubt that that is one reason
why thistles just about disappear in most parts of our pastures." To
ensure a healthy sod, Clark carefully manages grazing, fertilizes annually based
on soil tests, and topclips pastures once each season.
can become especially thick under permanent wires where stock sometimes root the
ground, -- creating bare spots -- but seldom graze or trample enough to kill the
thistles. Clip weeds in fence lines a couple of times a year before they go to
seed. Also avoid inadvertently bringing seed into uninfested pastures on
implements and animals or in weed-seed contaminated manure.
out the `thistle patrol.' Make a habit of carrying (and using) a hoe,
shovel, knife or bottle of herbicide, and chopping, digging, hacking or
squirting thistles every time you see them. Your persistence will pay off.
"I've been told by experienced graziers that cutting thistle is
most effective later in the season, when the core is hollow and reproduction is
underway," relays Clark. "When cut young, they say the thistles just
regrow. But I've always just hacked them off whenever I see them. After a few
years, they pretty well disappear, except near the fencelines."
the plant has gone to flower, do not just cut it off at the soil and leave it on
the ground, she cautions. "The flowers will continue to develop and seed
will fly. I cut off the developed heads when I find such a plant, and burn or
dispose of them elsewhere. As with quackgrass rhizomes, you must even be
careful where you spread the ashes," Clark jokes.
Gneiser, Berlin, Wis., suggests generously sprinkling some salt on the thistle
stump that remains after cutting to prevent regrowth, then using old twine and
diesel fuel to get the thistles' funeral pyre going. "I highly recommend
thistle patrol be delegated to farmers' children," he suggests. "Mine
also pull mustard (yellow rocket) and are compensated by the piece rate."
Spot spray 'em.
"I opt to do occasional spot spraying," says Cadwallader. "With
the vast acres of golf courses and lawns in our area, I don't think that the 1
or 2 liters of herbicide that I might judiciously use each year on my 150 acre
farm will cause any environmental disasters. Besides, I consider it therapy,
because I usually imagine someone's face painted on the plant. Some people use
punching bags, I zap thistles," he quips.
2,4-D is widely
used for thistle control, but one application is seldom enough to kill the
plants. This systemic herbicide usually will not kill or severely injure nearby
forage legumes. Overapplication may reduce 2,4-D's effectiveness by killing the
tops before much of the active ingredient moves to the roots.
University of Wisconsin study showed that 2,4-D works best when thistles are in
the rosette stage, usually in early May or again in mid-September in most of the
Dairy Belt. A rate of 1 pound of active ingredient per acre was sufficient to
kill virtually all of the plumeless thistles at that stage. But once they
started to bolt, a mix of .75 pounds of 2,4-D and .25 pounds of Banvel worked
Banvel at rates of 2 to 4 quarts per acre will produce
a near-total kill on actively growing thistles, but these high rates may also
kill forage legumes, and stunt grasses temporarily. Roundup doesn't work
very well on deep-rooted crops and will also kill surrounding forages, notes
Cadwallader. But both Roundup and Banvel can be wick-applied when thistles are
a foot or so taller than surrounding forages. In another Wisconsin study, two
passes of Roundup with a rope wick only partially killed Bull thistles, but
stopped their flowering totally.
Be sure to allow at least two or
three hours between application and rain to avoid having the chemicals wash off
the plants before they have a chance to take them up. Apply all herbicides
following label recommendations. Check with local Extension or ag chemical
dealers for more details.
them when they're weak. Perhaps the best time to spray thistles is in the
early fall, when temperatures are still in the 70s F. Nearly all of the plants
will be in the rosette stage and actively growing. At this point in the season,
the thistles are transporting sugars and starches to their roots for winter, and
so more effectively carry the herbicide down along with these nutrients than in
spring. Harsh winter weather will likely finish off most of the thistles that
the herbicide doesn't kill outright.
`kids.' Sheep and cows may nibble at young thistles up to 8 inches tall.
But goats relish them, especially the blossoms, virtually eliminating production
of new seed. "No grazier should be grazing cattle without goats as
companions," says Charles Reed, Linn Creek, Mo. "There is no other
enterprise that will control weeds and brush, improve the quality of the
pasture, and give you a paycheck to boot." Reed has found that he can run
two or more goats with each cow and generate an additional $150 or more in
income with about $50 in added expenses.
While no one wants thistles
in their pastures, keep in mind that not all weeds are necessarily evil
incarnate. Dandelions and dock, for example, can pack as much protein as
alfalfa, and can help fill in around more desirable species while pastures
mature. "Last summer I had a wonderful stand of a plant we call white
cockle show up in a pasture that was only a couple of years old," relates
Cadwallader. "The grasses were still a bit thin, and I had lost some
clover in a few spots so the cockle had very little competition.
75-year-old neighbor drove in the yard visibly upset and asked me what I was
going to do about my beautiful white-cockle stand. He grew up in the days when
the kids were sent out to pull weeds. I think he was expecting me to be
ashamed, since I'm a county agent. But when I said I wasn't going to do
anything, I think you could have knocked him over with a feather.
"I took him to the pasture where I had just turned in the sheep
to show him why I wasn't concerned," Cadwallader continues. "The
first thing they had eaten was the cockle flower itself, and then they went on
to the rest of the plant. To me as a shepherd, I didn't see the cockle as a
weed, but as a forage. My poor neighbor didn't know what to say. He just shook
his head and went home.
"This year the sod is stronger,
and the cockles are about gone."
|Let Weeds Take Care of Themselves!|
|Being trained in traditional agronomy, I tend to immediately think of weed
control in terms of direct chemical or mechanical action. But since becoming
involved with management-intensive grazing, and more recently Holistic Resource
Management (HRM), I now take a broader and longer-term view. |
control on my land is no longer primarily by chemical or mechanical means, but
by livestock impact. Yes, I still mow some, but mostly to maintain correct
grass maturity. And I also own a sulky-type weed-wiper, but am considering
converting it to a cart for my Newfoundland dog to pull in parades.
'94, most of the land that is now my 50 acres of pasture was abandoned vegetable
ground with a pH of 5.2. Twenty acres hadn't seen a crop in years and was
completely overrun with goldenrod, blackberries, wild strawberries and some
native grasses. Ten acres had been recently fallowed, and another 20 was in
In late '94, I disked some of the fallow area to
smooth it up, and planted 5 acres of winter rye. I also did some liming, but
University of Vermont pasture specialist Bill Murphy suggests that I might not
have even needed that expense. Then in Feb. '95, I frost-seeded 10 acres with
orchardgrass and white clover. While '95 was the driest growing season on
record, that 50 acres supported 60 stockers for more than four months. The
fallow land grew into orchardgrass, quackgrass, white- and red clover, and other
miscellaneous species including some weeds. The abandoned weedy area grew into
orchardgrass, some quackgrass, clovers, and native grasses, though it still has
some goldenrod and wild strawberries. Fortunately, the blackberries are very
sensitive to mowing. The long term hay area is still mostly timothy with some
clovers coming in, though I'm most disappointed with the speed of its change.
This year ('96), there is still a fair amount of bare soil and
some goldenrod and thistle out there. I don't like them. But until the bare
areas fill in with more desirable plants, I can see little point in not letting
the weeds exist. They may not be attractive, but they also aren't causing any
harm. If I manage the cattle grazing well -- which includes some mowing to
manage grass maturity -- the pasture will continue to convert to what I want.
Though it still has a lot of improvement to go, I expect it to compare favorably
with almost any other pasture in five years. But my cost of developing a quality
forage stand will be mostly management -- not cash.
To me, weeds
are a symptom of a problem -- not the cause. By managing cattle for the plant
species I want, the symptoms are going away quite rapidly. When the pasture is
higher quality, I may have less patience with weeds. But today I am tolerant due
to the progress I'm making, and I don't care to invest more money or mental
energy in eliminate them completely.
Nathan R. Leonard
Area Extension Specialist
©1997 Committee for
Sustainable Farm Publishing
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