Noxious Weeds

Controlling the Spread

Palmer Amaranth, Waterhemp, Marestail, Giant Ragweed, Lambsquarters, Pigweed, Burcucumber, Foxtail, Pokeweed, and Velvetleaf are some of the problem weeds we face annually in Knox County.  The first six weeds have documented herbicide resistance in Ohio.  The weeds in bold print are on the noxious weed list which requires control.

Arguably the single most daunting task facing some of us this year may be stopping the spread of weeds such as Waterhemp and Palmer Amaranth.  Waterhemp and Palmer Amaranth are two devastating, invasive weeds now found throughout Knox County.  These weeds, like no other weeds we have ever experienced, can and will change the way we manage our farms today.  These weeds can impact both your herbicide program and your trait-based seed selection.

Populations of these species can explode in just a few years if not controlled.  Consider each female plant of these two species can produce 1 million seeds.  If only one plant survives this year, how many of these seeds will germinate next year?  It’s not impossible to see a scenario where one surviving plant can turn into a million or more new plants within a few years.

Table 1. shows the seed production capabilities and the expected seed survival rate of different weed species prevalent in Knox County.

Controlling the spread

A monumental undertaking facing some this year will be to stop the spread of these weeds.  The most common avenues for weed seeds to spread are:

  • Machinery – Seeds are easily spread by many types of farm machinery, especially combines and mowing equipment.
  • Manure – Animals consume weed seed via various feed additives (cottonseed hulls) and hay.  Seeds are then spread in the manure.
  • Humans – Humans can spread weed seed through recreational activities and by moving items from field to field (power company moving big wood pallets).
  • Birds and wildlife – often transport weed seeds through their manure or by seeds in their coat.
  • Water – Heavy rains resulting in flooding can move weed seed to downstream fields.

Over the last three years I have personally seen evidence of weed seed movement throughout Knox County by each of these methods.

Invasive weeds pose significant risks to our farms.  Effective weed control programs and preventing the spread of these weeds is critically important.  These plants can have wide-ranging impacts on our farms for years to come.  Preventing these weeds from producing seed and/or removing or killing these plants before they produce seed is best way to control the spread.

 

Kill Poison Hemlock Now!

– Christine Gelley, Agriculture and Natural Resources Educator, Noble County OSU Extension

While hemlock may still be vegetative today, it will soon look like this.

Poison hemlock has already emerged in a vegetative state around Noble County and beyond. Soon it will be bolting and blooming on stalks 6-10 feet tall. All parts of the plant are toxic to all classes of livestock if consumed and is prevalent along roadsides, ditches, and crop field borders.

It is a biennial weed that does not flower in the first year of growth but flowers in the second year. The earlier you can address poison hemlock with mowing and/or herbicide application, the better your control methods will be.

 

 

 

Continue reading Kill Poison Hemlock Now! →

Suspected 2,4-D Resistant Waterhemp Population Discovered

Source:  ICM News, Iowa State University

We know the evolution of resistance in waterhemp populations happens faster than new herbicides are discovered, so the recent report of dicamba resistant waterhemp in Iowa by Bayer was not unexpected. Corteva has now reported the discovery of a suspected 2,4-D resistant waterhemp population in Iowa. These reports emphasize the need to use herbicides wisely and diversify weed management tactics beyond herbicides, especially as more farmers rely on herbicide group (HG) 4-based postemergence weed control in both corn and soybean.

The particulars

In late January 2024, Corteva reported the discovery of a suspected 2,4-D resistant waterhemp population in 2022 in Wright County, Iowa. A Corteva employee collected two samples of waterhemp seed, one from plants in the field and one from plants growing in the ditch adjacent to the field. While greenhouse testing with seed collected from plants in the field did not confirm resistance, plants grown from the ditch population are suspected to be 2,4-D resistant. The communication reported that the ditch had a multi-year history of 2,4-D application to manage broadleaf weeds. Corteva will continue evaluation of the populations in the greenhouse and the field. If resistance is confirmed in this population, it will become at least the fourth report of 2,4-D resistance in waterhemp, joining prior reports from Nebraska in 2009 (Bernards et al. 2012), Illinois in 2016 (Evans et al. 2019), and Missouri in 2018 (Shergill et al. 2018).

Iowa State University screened populations of waterhemp against several herbicides in 2019 at their 1X rates (Table 1). On average, waterhemp exhibited 17% survival to 2,4-D, 5% survival to dicamba, and 4% survival to glufosinate (Hamberg et al. 2023). We are rapidly losing herbicide options for postemergence control of waterhemp.

Best management practices to slow resistance development

Now is the time to evaluate how to improve weed management in fields. While herbicides will remain the primary tactic to manage weeds, farmers can implement several best management practices to slow herbicide resistance evolution and improve control of weeds like waterhemp.

  1. Choose an effective herbicide program for the weed spectrum present on a field-by-field basis.
    1. Use full rates of effective residual herbicides and plant into a weed-free seedbed.
    2. Include overlapping residual herbicides and multiple effective herbicide groups in postemergence applications to provide longer waterhemp control. Consult manufacturers for specific tank-mix recommendations.
    3. Make timely applications and choose appropriate adjuvants, nozzles, application volume, etc.
    4. Scout fields 7-10 days after postemergence herbicide applications to evaluate weed control.
  2. Use a diversity of weed management tactics, including chemical, mechanical, and cultural options. Narrow row spacing, cover crops, more diverse crop rotations, and tillage are effective tactics to suppress waterhemp.
  3. Control weed escapes prior to seed production to reduce future weed populations and prevent resistance from spreading.
  4. Reduce influx of weed seed into crop fields by managing weeds in field edges and cleaning equipment between movement from problematic fields to clean fields. The detection reported here indicates the threat of weeds in field edges.

Fall-applied Herbicide Considerations

Now that harvest is finally winding down, our thoughts change to fall weed control.   This is the best time of year to control winter annuals and some of the more difficult to manage overwintering weed species. Biennial and perennial plants are now sending nutrients down to the root systems in preparation for winter. Systemic herbicides like glyphosate and 2,4-D applied at this time will be translocated down into the roots more effectively than if applied in spring when nutrients are moving upward. This results in better control. In addition, the increasingly unpredictable spring weather patterns we have experienced in recent years can influence the timing and efficacy of spring burndown applications. Fall-applied herbicides can lead to weed free situations going into spring until early emerging annuals begin to appear in April, and are an essential component in the control of marestail and other overwintering species.

Here are some reminders when it comes to fall-applied herbicides:

  • Evaluate weed emergence and growth post-harvest to help determine if an application is necessary.
  • Fall-applied herbicides should primarily target weeds that are emerged at the time of application.
  • Species present in large quantities late-season that would necessitate the application of an herbicide include (but are not limited to): marestail, dandelion, wild carrot, poison hemlock, common chickweed, purple deadnettle, henbit, annual bluegrass, and cressleaf groundsel.
  • OSU research has not found much of a benefit from adding metribuzin or other residual products late in the fall. The exception to this is chlorimuron, which can persist into the spring. The recommendation here has generally been to keep costs low in the fall and save those products for spring when you will get more bang for your buck.
  • Herbicides generally work across a range of conditions, though activity can be slower as temperatures drop. Foliar products are most effective when daytime temperatures are in the 50s or higher and nighttime temperatures remain above 40.

Table 1 in the Weed Control Guide for Ohio, Indiana, Illinois, and Missouri provides ratings for various overwintering weed species in response to fall-applied herbicides.

The Ag Law Roundup: your legal questions answered

Source: Peggy Hall, OSU Extension

Is a tree service business considered “agriculture” for purposes of Ohio rural zoning?

No, tree trimming and tree cutting activities are not listed in the definition of agriculture in Ohio’s rural zoning laws, although the definition does include the growing of timber and ornamental trees. The definition ties to the “agricultural exemption” and activities that are in the “agriculture” definition can be exempt from county and township zoning.  Here is the definition, from Ohio Revised Code sections 303.01 and 519.01:

“agriculture” includes farming; ranching; algaculture meaning the farming of algae; aquaculture; apiculture; horticulture; viticulture; animal husbandry, including, but not limited to, the care and raising of livestock, equine, and fur-bearing animals; poultry husbandry and the production of poultry and poultry products; dairy production; the production of field crops, tobacco, fruits, vegetables, nursery stock, ornamental shrubs, ornamental trees, flowers, sod, or mushrooms; timber; pasturage; any combination of the foregoing; and the processing, drying, storage, and marketing of agricultural products when those activities are conducted in conjunction with, but are secondary to, such husbandry or production.

What are the benefits of being enrolled in the “agricultural district program” in Ohio, and is there a penalty for withdrawing from the program?

There are three benefits to enrolling farmland in the agricultural district program:

  1. The first is the nuisance protection it offers a landowner.  A landowner can use the defense the law provides if a neighbor who moves in after the farm was established files a lawsuit claiming the farm is a “nuisance” due to noise, odors, dust, etc.  Successfully raising the defense and showing that the farm meets the legal requirements for being agricultural district land would cause the lawsuit to be dismissed.
  2. The second benefit is that the law also exempts agricultural district land from assessments for water, sewer and electric line service extensions that would cross the land.  As long as the land remains in agricultural district program, the landowner would not be subject to the assessments.  But if the land is changed to another use or the landowner withdraws the land from the agricultural district program, assessments would be due.  The assessment exemption does not apply to a homestead on the farmland, however.
  3. A third benefit of the agricultural district program law is that it requires an evaluation at the state level if agricultural district land is subject to an eminent domain action that would affect at least 10 acres or 10% of the land.  In that case, the Director of the Ohio Department of Agriculture must be notified of the eminent domain project and must assess the situation to determine the effect of the eminent domain on agricultural production and program policies.  Both the Director and the Governor may take actions if the eminent domain would create an unreasonably adverse effect.

Continue reading The Ag Law Roundup: your legal questions answered →

Is it Pigweed or Palmer? – Hope it’s not Waterhemp!

It’s that time of year when weeds are beginning to show their ugly heads above the soybean canopy in many fields.  During your scouting, if you find Palmer Amaranth or Waterhemp you should do whatever you can to prevent these devastating weeds from going to seed, including removing the entire plant from the field.

Each of the last 3 weeks I have included a post highlighting the different characteristics of Pigweed, Palmer Amaranth and Waterhemp.  These posts also included a step by step video to help with the identification process for these weeds.

Depending upon the growth stage, identifying these weeds in the field can be challenging. If a seedhead is present, most weeds are easier to identify, including pigweed, palmer and waterhemp. If you have seen a mature palmer seadhaed you will never forget it!  (see pictures above)

When trying to differentiate between these weeds I look for the following 3 plant characteristics:

1.Hair

Pigweed has hair the others do not.  Rub the stem and leaves checking for a “rough” texture.  Palmer and waterhemp will be smooth.

 

2. Leaves

Long Lanceolate Leaves

Waterhemp has long, slender leaves (lanceolate). While pigweed and palmer are more oval in shape.  Pigweed is wider in the middle and palmer is wider near the base of the leaf (this is usually hard do differentiate in the field).

 

 

3. Petiole

The petiole is the part of the plant that connects the leaf to the stem.  The petiole on palmer plant is as long or longer than the leaf.  Pigweed and waterhemp have much shorter petioles (often less than 1/2 the length of the leaf).

These weeds are here, they best way to prevent the spread is by preventing them from developing a seedhead.  One mature female plant  can produce up to 1,000,000 seeds.

 

Weed Identification Videos

 

If you  are still not sure about the identification, do not hesitate to call 740-397-0401) or send (barker.41@osu.edu) me a picture!!!

2023 Regional Weeds University

OSU Extension invites crop producers, CCAs, and agribusinesses to attend a regional 2023 Ohio Weed University on Wednesday, March 1, from 9:00 a.m. to 4:00 p.m. at the Ramser 4H Activity Center, 700 Perimeter Dr. Mount Vernon, OH.

This program is designed to keep agronomic producers on the cutting edge in weed control for their cropping operations. Topics addressed will include hot topics in weed control, local weed issues, biology, identification of weeds, control strategies, and evaluating herbicides. Hands-on exercises weed identifications will be included.

Featured speakers will include Dr. Aaron Hager, Associate Professor, Department of Crop Sciences, University of Illinois; Dr. Patrick Tranel, Professor, Weed Science, University of Illinois; Dr. Alyssa Essman, visiting Professor and acting State Weed Specialist, The Ohio State University; and, Tony Dobbels, Research Specialist, The Ohio State University. This is an “in-person” event with a of the program being conducted virtually at the above locations.

Dr. Hager contributes to increased crop production through the development and implementation of integrated weed management programs. His research helps to identify and manage herbicide resistance in the most aggressive agronomic weeds. Dr. Tanel’s research and teaching is based on weed science, with an emphasis on the evolution, genetics, molecular biology, and genomics of agronomic weeds. His specialties include herbicide resistance and weedy Amaranthus species. Dr. Essman’s research is setting up a long-term research project looking at the effects of cover crops and herbicide inputs on waterhemp populations and seed bank dynamics. Dobbels manages the herbicide evaluation and field research program in row crop weed control at Ohio State.

The registration fee per person is $40.  Call OSU Extension 740-397-0401 to register.  

Registration deadline is Monday February 27.

Click here to view agenda