November’s Weed of the Month is Palmer amaranth (Amaranthus palmeri). This fast growing weed has developed resistance to multiple herbicide modes of action so it is difficult to control. Palmer amaranth produces a lot of seed, up to 250,000 per plant, and is highly competitive. It spreads quickly and will cause extensive corn and soybean crop losses.
Palmer amaranth is native to the arid southwestern United States and northwestern Mexico. It was accidentally introduced to the southeastern United States and became the most troublesome weed in cotton production, by far. It developed resistance to many herbicides with multiple modes of action and spread to row crop fields in much of the eastern half of the country. This dreaded weed was discovered in Minnesota in 2016.
Palmer amaranth plant with seed spikes. (photo provided by the Minnesota Department of Agriculture.)
Palmer amaranth can be distinguished from closely related waterhemp and other pigweeds by a long petiole length and very tall flower and seed spikes. Unlike other pigweeds, Palmer petioles are often longer than the leaf blades. A petiole attaches a leaf to a stem. The flowering spike is much longer than that of other pigweeds. Leaves of some Palmer plants have a whitish V-shaped mark on them. Palmer amaranth is a summer annual that commonly reaches heights of 6-8 feet but can reach 10 feet.
ST. PAUL, Minn. – Crop scientists at the University of Minnesota and officials at the Minnesota Department of Agriculture (MDA) urge farmers to check fields for Palmer amaranth, an aggressive weed that can put corn and soybean crops at risk. A plant detected in a native seed planting plot on a Yellow Medicine County farm was confirmed today to be Palmer amaranth. This is the first confirmation of the weed in the state.
The MDA asks possible infestations to be reported by contacting the MDA’s Arrest the Pest line by phone at 1-888-545-6684 or by email at email@example.com. Landowners are encouraged to email photos of suspected infestations for identification.
“We encourage landowners to scout fields now before harvest for Palmer amaranth and report any possible infestations to the Minnesota Department of Agriculture,” said Geir Friisoe, MDA’s Director of Plant Protection. “The quicker we’re able to identify and start managing this weed, the better our chances will be to minimize the impact to our ag industry.”
Palmer Amaranth has been found in Minnesota and the Department of Agriculture wants farmers to keep an eye on their fields to help nip this in the bud before an infestation can occur. (Photo by Bruce Potter)
Palmer amaranth can grow 2 to 3 inches a day, typically reaching 6 to 8 feet, or more, in height. Left uncontrolled, a single female Palmer amaranth plant typically produces 100,000 to 500,000 seeds. It is resistant to multiple herbicides.
It has been found in 28 other states, including Iowa, South Dakota, and Wisconsin.
“Palmer amaranth infestations have caused substantial yield losses and greatly increased weed management costs in cotton, soybeans, and corn in the southern states,” said Extension agronomist and crops leader Jeff Gunsolus. “This is a disconcerting, though not completely unexpected, discovery in Minnesota. We have been discussing proper identification procedures with crop consultants over the last three or more years.”
Palmer Amaranth has been found in Minnesota fields and it’s important for farmers to watch their fields in order to avoid an outbreak in farm fields across the state. (Photo by Bruce Potter)
Extension and MDA officials commend the grower and crop consultant who quickly contacted Extension after discovering a suspected Palmer amaranth plant. The weed is on MDA’s prohibited-eradicated noxious weed list, requiring all above- and below-ground parts of the plant be destroyed. Transportation, propagation or sale of the plants is prohibited.
MDA and Extension continue coordinating action steps to address the weed.
The MDA is investigating how the weed may have been introduced to the state.
Steve Olson is director of the Minnesota Chicken and Egg Association. He says the push to move producers to cage free production methods will double the cost of production, and drive up the cost of eggs at the grocery store. (photo from BrownfieldAg.com)
Time to hit some agriculture highlights, and eggs, weather, and weeds all get some time on the air today. Let’s do another edition of the ChadSmithMedia weekly podcast on chadsmithmedia.com. This week, we’re talking about cage free eggs in Minnesota. Steve Olson of the Minnesota Chicken and Egg Association says get ready for the cost of your scrambled eggs to get even higher. A large Minnesota grocery chain will be buying only from cage free producers in the coming years, and that will do nothing but double the cost of production for the farmers who make those sunny side up eggs possible.
Iowa State climatologist Elwynn Taylor said he expects good growing conditions during the season ahead, and if El Nino sticks around, there’s a chance yields may come in slightly above trend line in the fall. (Photo from extension.iastate.edu)
We’ll also discuss weather, which has to be one of my favorite topics because you’re guaranteed to get different answers from each person you talk to. Elwynn Taylor is the Iowa State University Extension Climatologist, and he’s talking about yields after this growing season possibly coming in slightly above trend, but that could depend a lot of El Nino sticking around, and reports have come in about the phenomenon actually beginning to weaken. Should be interesting to monitor during the growing season.
Lastly, we talk a lot about scouting weeds, and we have a reminder from Chris Reat of FMC to get your scouting done before spring planting, and be diligent. We’ve talked a lot about resistance issues, especially around glyphosate, and it’s always good to mix up your program as you tackle grasses and broadleaf weeds.
There you go. I do enjoy podcasting, and would love to know what you want to hear in the months ahead.
Many management strategies, including prescribed burns, can be used against invasive plants.
In most cases, no single strategy used by itself will provide the desired long-term solution that landowners and managers seek. However, when used together as part of a larger integrated strategy, they can provide significant benefits for achieving successful, long-term management.
A prescribed burn is used as an invasive plant control tool, and to manage native plant communities and large landscapes.
At the Minnesota Department of Transportation (MnDOT), one goal of prescribed burns is to improve the health of desirable vegetation. Ken Graeve with MnDOT says they use prescribed burns to promote the growth of desirable vegetation in combination with other treatments such as herbicide applications. With these combined methods, a healthy ecosystem is better able to outcompete invasive plants.
The Minnesota Department of Natural Resources (DNR) uses prescribed burns not just for managing native plant communities, but also for controlling woody invasive plants.
An autumn prescribed burn is used to improve the health of native vegetation at a wetland mitigation. (Contributed photo)
For example, after initial work of cutting and treating with herbicide application, the DNR may use prescribed burns in subsequent months and years to help control infestations of buckthorn, honeysuckle, or Japanese barberry. Shawn Fritcher from the DNR says prescribed burns can be effective against these invasive woody plants because burns can cover large areas faster than cutting and treating can. Multiple burns are often needed to reduce the vigor of woody invasive species.
Fritcher also says it is important to note that repeated fire is most appropriate in fire-dependent woodlands.
At both MnDOT and the DNR, staff who work on prescribed burns go through training. They learn about fire behavior, weather prescriptions, and how to design and write an effective burn plan. Fire breaks, or the breaks in combustible material, are often established ahead of time using a variety of equipment like tractors, mowers, ATVs, rakes, and leaf blowers. Fire breaks are controlled using trucks or ATVs that carry water, or with hand tools where access by ATV is limited. The appropriate permits must be acquired, and traffic control measures are utilized for burns along roadsides.
Timing prescribed burns depends on the management objective. Desirable plant species often respond well to early spring burns. Smooth brome and other cool season grasses can be managed with late spring burns. Burning woody invasive species after leaf-out may be the most effective since much of the plant’s energy is invested in new above ground growth. Summer burns can be effective at controlling brushy species in prairie areas. Fall burns provide another opportunity to target some invasive species.
For landowners thinking about utilizing prescribed burns, they must first get a burn permit.
Farmers use prescribed burns intheir fields to encourage growth by removing competition from weeds (Photo from farmprogress.com)
Proper planning for the burn is critical to success. The landowner needs to think about many factors such as fire break location, wind direction, smoke, control measures, and many other parameters to make decisions for the burn plan. There are multiple resources through the DNR website (http://www.dnr.state.mn.us/rxfire/index.html) to assist landowners with planning prescribed burns.
February’s Weed of the Month is about the poisonous ornamental plants that may be found growing in Minnesota community gardens. Some poisonous plants commonly grown in gardens have specific parts which are safe to eat (like tomatoes or other nightshades), while other plants are entirely poisonous. We will focus on plants which are wholly poisonous. The most common of these in Minnesota are castor bean, jimsonweed or Datura, and foxglove.
The castor bean plant is an African transplant into Minnesota whose seeds contains ricin, an incredibly toxic compound. Be careful to avoid accidental ingestion. (contributed photo)
Castor bean plant, or castor oil plant, (Ricinus communis) is native to Africa and occasionally grown for medicinal and ornamental purposes in Minnesota. It has become naturalized in tropical and subtropical regions throughout the world, such as California. In Minnesota, it is a robust annual, growing to heights of 6- 15 feet. It has large, colorful, palmate leaves and pink or red flowers found along its stalks, which become soft, spiky, fruit-containing balls. The seeds contain ricin, an incredibly toxic compound which can be deadly if ingested. Ricin also occurs in lesser amounts in tissue throughout the plant. The seeds of this plant are so poisonous, it is said that ingestion of a single seed can kill a child. For this reason, castor bean should not be planted in any area that might be accessed by children, such as a community garden.
Jimsonweed is an annual ornamental plant occasionally grown in Minnesota. All parts of the plant, including seeds, contain alkaloids, which are toxic when ingested. (contributed photo)
Jimsonweed (Datura stramonium) is an annual ornamental plant in the Nightshade family occasionally found growing in Minnesota. It grows to a height of two to four feet and has long, trumpet-shaped, white to lavender blooms which extend above the leaf canopy, and distinctive, spiky, ball-shaped fruit. All parts of this plant, including the seeds, contain alkaloids which are toxic when ingested. If the plant were to go to seed, it could spread seedlings around a garden, which could then become intermixed with crops and accidentally ingested. Jimsonweed historically has been used as a recreational drug, occasionally resulting in overdose and death. The potential for accidental or intentional poisoning is high enough that it is advisable to prohibit these plants from growing in a garden alongside edible crops.
Foxglove is occasionally planted in Minnesota for ornamental purposes, but the entire plant is extremely toxic if ingested. It’s also a self-feeder, and can become extremely invasive if left unchecked. (contributed photo)
Foxglove (Digitalis purpurea) is a popular biennial ornamental plant. The foliage begins as a basal rosette in the first year. In the second year, it sends up long stalks which grow up to five feet tall and are lined with trumpet-shaped flowers. Many varieties are available, with flower colors ranging from white to pink to yellow. It is commonly grown to attract pollinators like bumblebees and hummingbirds. The entire plant is extremely toxic. Intentional ingestion can occur by individuals seeking medicinal folk-remedies and accidental ingestion by confusing foxglove with other edible herbs or by curious children. Foxglove is also prolific self-seeder and can become an aggressive invasive weed.
The best way to prevent issues with these plants is not to plant them in the first place, or strictly limit them. These plants, and all poisonous plants, should be prohibited from any community garden. They should not be planted anywhere where children might encounter them or close to any edible crops. Please contact Minnesota Poison Control with any concerns about potential human poisoning at 800-222-1222, firstname.lastname@example.org, or www.mnpoison.org.
Garlic mustard is an edible, biennial herb that emits a strong garlic odor. It was brought to the United States from Europe as a culinary herb. It has naturalized in many eastern and midwestern states.
In Minnesota, it is widespread in the south and is spreading north. The bad news is garlic mustard is highly invasive. It grows in woodlands, and along trails and waterways. It outcompetes native plants, becoming detrimental to wildlife habitat and biological diversity.
Garlic mustard forms rosettes after seed germination in early spring. In its second year, it forms upright stems that produce flowers in May and June. Seeds begin to develop in slender pods shortly after flowering and are the plants’ primary means of spread.
The plant has distinctive characteristics to distinguish it from other woodland plants. In the rosette stage, the leaves are heart-shaped with toothed margins. When it matures, the leaves along the stem are triangular and the small, white, four-petaled flowers are produced in clusters at the tops of the stems. The plant produces slender seed capsules. Seeds can be spread by water and soil movement on boots and equipment.
Garlic mustard is a restricted noxious weed and cannot be transported, sold, or intentionally propagated in Minnesota. It is recommended that this species be prevented from spreading to new areas and that smaller populations be eradicated.
Managing garlic mustard takes persistence and a focus on preventing flowering, making timing a key component to management.
Regular site monitoring for several years will be required to ensure that new seedlings are destroyed and the seedbank is depleted.
Hand pulling may be practical for small infestations. Pull plants prior to flowering to prevent seed production. Flowering plants can continue to set seed following removal of soil.
Mowing of bolted plants prior to flowering can prevent seed production. All equipment should be inspected and cleaned prior to moving into new areas.
Foliar herbicide applications may be effective. If using herbicide treatments, check with your local University of Minnesota Extension agent, co-op, or certified landscape care expert for assistance and recommendations.
Lisa Behnken of the University of Minnesota Extension Service in Rochester, Minnesota (Photo from Extension website http://r.umn.edu/academics-research/extension/staff/UMR_EXTENSION_STAFF_L_BEHNKEN.html)
“Corn is looking very good across the area,” said Behnken. “That’s the crop that’s probably outstanding. The general region had good planting dates and some very timely rains in most of southeast Minnesota. It has been a little bit wet in certain areas, and some spots did see some hail. Overall, the corn crop looks good and has had a very good growing season.”
Soybeans are a different story. She said the soybeans have had a rougher go of it.
“And they may even have a rougher go between now and the end,” said Behnken. “There are some fields that look beautiful, but there are some different things happening in area fields. Some of it has to do with the amount of moisture we’ve received. In some cases, it’s been too much moisture, and that’s led to some problems for bean here in late August, into early September.”
Weeds are becoming a big challenge in area soybean fields.
“You have some fields that are very clean,” said Behnken, “with maybe a corn spear or weed here and there. On the other side of the equation, we have a lot of fields with Waterhemp coming through in soybeans. In other cases, you may see giant Ragweed, or even a mixture of weeds like Velvetleaf and Lamb’s Quarter, but the big one people are talking about here, and around the state, is Waterhemp.”
So, why is Waterhemp a problem?
“It germinates a little later in the spring,” said Behnken, “but it can germinate all through the growing season. When the canopy doesn’t close right away, the weed will keep germinating through the season.”
Behnken has a theory on why soybean canopies are closing later than they have in the past. She called it a Catch-22:
The bigger question is what a farmer did early in the season to treat fields for weed development.
“What did people do for their herbicide program,” said Behnken. “If you did not use a residual herbicide in your pre-emergence program, or in some cases, come back with a residual in your post-emergence program to keep those herbicides working all season, then Waterhemp has an opportunity to take off.”
According to Lisa Behnken of the University of Minnesota Extension Service, Waterhemp is becoming a challenge in SE MN Soybean fields. (Photo from soilcropandmore.info)
She added, “We’re also talking about resistance issue now. Waterhemp has some resistance to the ALS chemistry, and we’ve just confirmed some resistant pockets to another class of chemistry we call PPO’s.”
Area soybeans are struggling with some disease pressure as well.
“One that’s difficult to manage is white mold,” said Behnken. “I see it going east of Rochester throughout eastern Olmsted County including Winona and Wabasha and even into Fillmore County. If you notice uneven canopy development and walk out into the field, you should see some white mold. White mold likes wet conditions, and east of Rochester saw quite a bit of steady rain.”
Behnken added, “It’s a very difficult disease to treat, and while fungicides control other diseases in soybeans, there are more limited options to take care of white mold. It’s definitely going to cost some yield in certain fields.”
Bean challenges don’t stop there.
“We always wonder when aphids will hit us, and this year they hit us in August again,” she said. “The weather earlier this year kept them at bay. Toward the end of July, we saw a mass migration when aphids came in on westerly winds. Once they arrived and got established, they exploded in numbers really fast. Growers need to keep a sharp eye on their fields.”
The area’s alfalfa crop has turned out well in spite of frequent early season rains.
“We’ve put up a lot of hay this year,” said Behnken, “mostly in between rain storms. The good part of it is if you do have rain, then you have a crop. We know how to deal with hay that gets rained. We chop a lot more hay and we round bale, then you categorize it based on quality and how much rain damage there is. We’ve put up a good crop, so there’s good feed out there.”
If it’s been awhile since you’ve seen white mold in your fields, here’s a good refresher at spotting white mold in soybeans, courtesy of the University of Wisconsin Extension Service:
by Emilie Justen, Minnesota Department of Agriculture
(This is part of a series of regular columns by the Minnesota Department of Agriculture on the state’s noxious weeds.)
Black swallow-wort vines with flowers (Photo from the Mn Dept of Agriculture)
A member of the milkweed family is November’s Weed of the Month. Black swallow-wort (Cynanchum louiseae), also called dog-strangling vine, is a perennial, herbaceous vine that can form large patches and crowd out native vegetation. It was introduced to North America from southern Europe in the 1800s as an ornamental plant, and in 1864 was recorded escaping from a botanic garden in Massachusetts. Since its introduction to North America, it has been found invading abandoned farm fields, pastures, and prairies throughout the Eastern and Midwestern United States.
Black swallow-wort has twining stems up to six feet long. It has dark green, glossy foliage and star-shaped, dark purple flowers with a yellow center. The flowers are only 1/8 inch in size, and develop into a milkweed pod to disperse its seed by the wind.
The plant poses many ecological threats to the Midwest. It outcompetes native plants by forming a large root system that exudes chemicals to prevent other plants, such as the native butterfly milkweed, from growing. Black swallow-wort also threatens monarch butterflies by crowding out native milkweed host plants. In addition, female monarchs will lay their eggs on black swallow-wort but the plant is lethally toxic to the caterpillars after they hatch and begin feeding. It can also thrive in wooded areas to form a monoculture in the forest understory. In Minnesota, black swallowwort was found growing on the University of Minnesota’s St. Paul campus and successful eradication efforts kept the infestation from spreading. There are two reports of isolated infestations in Minneapolis.
Black swallow-wort’s characteristics make it a challenge to control. It grows over other vegetation to block light and create tangled masses. As a target weed on Minnesota’s Noxious Weed Eradicate List, it is required by law that all above- and below-ground plant parts must be destroyed. Recommended management practices for black swallowwort include the following:
Pulling the plants by hand can be difficult and cause resprouting.
Burning and grazing have not shown to be effective.