Noxious Weeds

Musk Thistles

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rose leaf
rosette

Fall is a great time to control Musk Thistles

Musk thistles are a major threat to pastures and rangelands, and their destruction can spread quickly.  The good news is, fall is an excellent time to control the prickly pest. Dry summers and grazing add up to ideal conditions for musk thistle.  Now is the cheapest time to spray for musk thistle and we have always had excellent results from a fall application.

Unfortunately, when musk thistle goes untreated, it infests wider areas. Uncontrolled, a large musk thistle plant can produce 15,000 seeds – roughly half are viable.  That’s 37.5 million viable seeds from an acre moderately infested with one plant per square yard.

Some biocontrol agents have been introduced with limited to moderate success, but they cannot do the job alone.  Musk thistle is relative easy to control with herbicides, when applications are timed right.  Best results come from treatment during the weed’s rosette stage.  Bolted thistles are hard and expensive to control.

View musk thistle control as a part of grass management.  Weakened pastures are vulnerable to blowing seeds.  A thistle-infested pasture cannot support the same stocking rate as good, lush grass.  Cattle will overgraze the good grass, allowing the thistles to spread onto weaker areas.  Thus, the problem just gets bigger.  A good fall herbicide program not only can provide excellent musk thistle control, it also gives producers and applicators the time to do it.  In addition, since rosettes are controlled early in their life cycle, the weeds are much less to damaging to pasture. 

In general, fall application for musk thistle starts around October 1, but can  begin  earlier, depending on the year.  In many areas, fall spraying for musk thistles can continue into the month of December until the ground freezes, or until rosettes stop growing after a hard , killing frost.

Treatment Options

  • Tordon 22K (RUP)  8 oz. per acre.
  • Escort  1/3 oz. per acre.

Be sure to use a good non-ionic surfactant, in addition, to ensure greater absorption of the herbicide.

Spring spraying is an option when weather shuts down fall spraying or for cleaning up any thistles missed during the fall.  However spring treatments cost more because they require including 2,4-D in the tank mix.  After the thistles bolt, you’ll need to increase herbicide rates.

The time and expense necessary to hold down musk thistle during the spring and summer make fall control especially appealing, it’s simply a more convenient, effective and economical time to treat.

Sericea Lespedeza

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Sericea Lespedeza seedling

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Sericea Lespedeza starting to flower

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Sericea Lespedeza untreated

Sericea Lespedeza is an introduced perennial legume native to eastern Asia.  It was first recognized as a potential weed problem in southeast Kansas in the early 1980’s.  Sericea Lespedeza is most common in the eastern third of Kansas, but has spread west, with more than 70 counties reporting its occurrence statewide.  More than 500,000 acres are currently infested by sericea lespedeza, with an estimate of 40,000 acres infested here in Cowley County.  It was declared a statewide noxious weed July 1, 2000.  Sericea lespedeza is the first federally listed crop to be declared a noxious weed.

Once established, sericea lespedeza plants will reduce or eliminate competing vegetation.  It is relatively slow to establish, having a rather weak and vulnerable seedling stage.  At the same time, this opportunistic invader will establish itself in full sun or partial shade.  Sericea lespedeza tolerates shade quite well, establishing itself in dense shade where direct sunlight does not reach.

Sericea lespedeza has been recognized as a quality forage due to its high levels of crude protein.  However, livestock does not like to graze sericea lespedeza because of the high tannis.  Tannis binds with proteins, causing the proteins to be unavailable for digestion.  This combination makes sericea lespedeza unpalatable and reduces intake and digestibility.  The level of tannis appears to increase with maturity of the plant, high air temperatures, and low rainfall.  The tannis also reduces insect feeding.

Treatment

Remedy, Remedy/Vista are recommended for spring treatment.  As the sericea lespedeza matures and starts to flower, for best results Escort applications can be made from bloom stage through first frost, (killing freeze).  DuPont recommends a mix of ½ oz. to 1 oz. per acre with a good surfactant.  There are no grazing restrictions using Escort at a rate of up to 1 2/3 oz. per acre.  Escort is non-volatile, non-flammable and does not pose adverse affects to humans, livestock and wildlife when used according to label instructions.  Escort is kind to native grasses and is not a “restricted use” herbicide.

Field Bindweed

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Field Bindweed seedling.

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Field Bindweed leaf and flower

The perennial field bindweed destroys crops and can lower net profit because it is so aggressive and persistent.  The weed’s ability to reproduce in semi-arid conditions makes it tough for farmers across the Great Plains.  And like any perennial weed, it must be controlled in a planned manner.

Field bindweed can produce 500,000 seeds per acre and the seeds remain viable for up to 60 years.  While seedlings menace your farm, it’s what you can’t see that can really hurt you.  Bindweed can send a root system 30 feet deep.  A tough, deep-rooted “mother plant” spawns an array of new shoots.

The roots are like a food bank, nourishing new growth from shoots.  Once new shoots form new leaves, they start replenishing the colony in 12 to 16 days, sending nutrients back down into the system.

The roots can steal moisture which limits crop yields, even when crops themselves cannot reach soil moisture.  Controlling the root system is the goal of any effective bindweed management program.

Recommendations for control of Field Bindweed:

  1.       The most effective control program includes preventive measures over several years.
  2.       Banvel, Tordon, 2,4-D, roundup products alone or in various combinations are registered for suppression or control of field bindweed in fallow and/or in certain crops, pastures, and rangeland.  Apply each herbicide or herbicide mixture according to directions, warnings, and precautions on the product labels.  Single herbicide applications rarely eliminate established bindweed stands.
  3.       Applications of 2,4-D, Roundup products are most effective when spring applied to vigorously growing field bindweed in mid to full bloom.  However, Banvel and Tordon applications are most effective when applied in the fall.  Most herbicide treatments are least effective when applied in mid-summer or when bindweed plants are stressed.