Keeping a lid on hoary cress | TSLN.com

Keeping a lid on hoary cress

Hoary cress is one of the earliest weeds to sprout in the spring. Scouting for it while it is in the rosette stage, as shown, is critical, as this fast growing stage is when spraying is most effective. Photo by Jan Swan Wood.

Hoary cress, a weed declared noxious by the state of South Dakota, is rapidly spreading across not only South Dakota and other western states, but is creeping farther east every year. In South Dakota, Butte County has the highest detected amount of the perennial weed.

Butte County landowners were invited to a meeting about hoary cress by the Butte County Weed and Pest. Meetings were held on April 8 at Nisland and Belle Fourche. Speakers included Mike Stenson from the South Dakota Department of Agriculture, Meghan Foos, Agronomy specialist with CBH Cooperative, and Corey Morris, representative for Van Diest Chemical Supply Company. Bill Erk and Don Adams, Butte County Weed and Pest, as well as Clint Pitts, Weed and Pest Board member were also present and available to talk to attendees.

Hoary cress is from the mustard family and is also called white top and perennial peppergrass. A native of Eurasia, it was introduced to the United States in contaminated seed. It is a relatively long-lived plant with rhizomatous roots, which spread in a network underground. The network of roots can create over 450 shoots and cover an area 12 feet in diameter in one year. A single 3-year old plant can produce 1,200-4,800 seeds per year, with seeds generally surviving three to seven years in the soil.

Adaptive to many soil types, it thrives in alkaline soils and is drought resistant with roots that reach 30 inches to up to 30 feet in depth. Hoary cress spreads both by root and seed and has the potential to take over very large tracts of land. With optimum conditions, hundreds of acres are blanketed with the plants, as was demonstrated during a slide presentation by Meghan Foos.

A cold season perennial, hoary cress is often the first forb that sends up leaves in late March and early April. It uses the available moisture and can choke out other plant growth. With a root system that can double annually, it thrives under low competition with other plants, so overgrazing contributes to its success.

Similar in appearance to another mustard family plant called penny cress, one can see the difference with closer examination. Hoary cress has a blue/gray tint to the leaves while penny cress is a bright, medium green. Once established, penny cress can be pulled up easily while hoary cress is very hard to pull up due to its extensive root system. Penny cress is also an annual.

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Seed can spread by wind, water, livestock, wildlife, vehicles, machinery, hay bales and even muddy boots. It can contaminate mulch, feed, crop and grass seed, top soil and gravel and be transported in them. Its invasive quality can lead to substantial losses on both grazing and hay land. Both production volume and feed quality are affected. Hoary cress isn't a poisonous weed, but if ingested it can cause problems. Foos explained, "Hoary cress contains glucosinolates which irritate the mucous membranes in the mouth of the animal. The animal will graze less due to the mouth and tongue being sore, so they lose condition." She also pointed out that it passes through the milk and will affect the calf or lamb as well. Livestock will only graze it when forced to, due to lack of other forage.

Controlling hoary cress requires scouting for plants and effectively applying a herbicide. Since the plant must transport the herbicide into the root system to kill it, spraying must be done when the plant is in a stage of rapid growth. "As the plant matures, the spray is less effective," said Foos.

Andrew Canham, commercial applicator from Miller and Spearfish, South Dakota, concurs, "Timing on hoary cress is critical. Once it's bloomed, it's too late," said Canham, adding "The key is to be ready before it starts to grow and then when it does, plan on going out repeatedly to spray. The toughest part is finding it, as it sprouts in old growth that hides it."

The chemical of choice, and the one available at no cost through the grant from the South Dakota Weed and Pest commission, is Escort XP. Foos recommends Escort as it stays in the soil for up to three years and can remain in the soil to kill later-sprouting seed.

Foos also recommends adding 2-4-D, Estes or Amine to the Escort XP, plus a good surfactant, such as Powerlock, Premier 90 and Preference. If other weeds are also being targeted, one can add Chaparral or Milestone. Drift control is also important, especially when spraying near other fields and in windy conditions, so she recommends Base or Guardian for that purpose. "Alfalfa can't stand Escort, so keep that in mind when you are spraying," added Foos.

For spot spraying, the formula is as follows:

64 ounces (1/2 gallon) warm water

1/2 ounce Escort

2 ounces surfactant

1 teaspoon of household ammonia (helps dissolve the Escort)

Mix thoroughly.

Add eight ounces of this mixture to 3-4 gallons of water, mix thoroughly again and use within 70 hours.

Keeping the spray well-mixed is critical according to both Foos and Canham. "Don't just dump it all in the tank and head for the field and start spraying. Really mix it up or all of the Escort will be in the bottom of the tank," said Canham.

Landowners in Butte County can apply for the no cost Escort XP by contacting the Butte County Weed and Pest office at 605-456-1313 for the form, which needs to be back to the office as soon as possible. Distribution of the Escort XP will begin right away and it's on a first come, first served basis. Bill Erk will deliver the product to the landowners.

Andrew Canham will be available for commercial application of the product, but landowners who choose that route need to get on his list right away so as to get the hoary cress sprayed at an optimal time. His number is 605-530-8089.

Landowners with hoary cress on their property can either address the problem themselves, utilizing the free chemical available, or be required to by the county. If the county has to do the spraying, the landowner will be charged for the work.

Now is the time to be scouting pastures, lots and right of ways for hoary cress. Eradicating it before it takes over is much easier, and the old saying "an ounce of prevention is worth a pound of cure" really applies in this case.