Weeds

Kill Poison Hemlock Now!

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

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.

Poison hemlock is a concern in public right of ways, on the farm, and in the landscape!

Poison hemlock is related to Queen Anne’s lace, but is much larger and taller, emerges earlier, and has purple spots on the stems. Another relative that is poisonous is wild parsnip, which looks similar to poison hemlock, but has yellow flowers. Giant hogweed is another relative of poison hemlock that is also toxic. All of these plants have umbel shaped clusters of flowers.

Continue reading Kill Poison Hemlock Now! →

Last Chance: Pesticide and Fertilizer Recertification Meeting March 24th

If you have an Ohio Pesticide or Fertilizer Applicators License it will expire on March 31, 2022. We will be holding the final opportunity for recertification in Northwest Ohio on March 24th at 5:ooPM. The event will be held in the Youth Activities Building on the Allen County Fairgrounds. The fertilizer session (Category 15) will run from 5-6pm followed by the pesticide portion (Categories 1,2,6 and Core) Please register today by calling us at (419) 879-9108 or by email at schroeder.307@osu.edu  Registration cost is $10 for fertilizer recertification and $35 for pesticide recertification and includes educational materials and refreshments. The registration fee can be paid at the door with cash or check made out to OSU Extension – Allen County. This fee is separate from the Ohio Department of Agriculture license renewal fee of $30.

2021 Allen County Weed Survey

By Clint Schroeder OSU Extension

Each fall Ohio State University Extension conducts a survey of the different types of weeds present in soybean fields, as well as, the level of infestation. Weed Science State Specialist Dr. Mark Loux leads this study and uses the information gained to help develop future weed management programs. This study is conducted in each county where there is an Ag and Natural Resources Educator. The educator selects a route 80-100 miles long through the county and takes notes on one soybean field in each mile.

A total of 82 soybean fields were observed in Allen County this year.  Waterhemp and volunteer corn were the most prevalent and present in 30% of the observed fields.

2021 Allen County Weed Survey Results

Continue reading 2021 Allen County Weed Survey →

Five Things to Know about Fall Herbicide Treatments

By:  Mark Loux OSU Extension

There is plenty of information on fall herbicide treatments in the C.O.R.N. newsletter archive and on other university websites.  Our philosophy on this has not changed much over the past decade.  A few brief reminders follow:

1.  When to spray?  Anytime between now and Thanksgiving will work, and possibly later.  We have applied into late December and still eventually controlled the weeds present at time of application.  Once hard freezes start to occur, there is usually a substantial change in the condition of certain weeds, such as dandelion and thistle, that renders them less sensitive to herbicides.  We discourage applications during periods of very cold weather which can occur starting about Thanksgiving, and also (obviously) when the ground is snow-covered. Continue reading Five Things to Know about Fall Herbicide Treatments →

Get your Waterhemp Populations Screened for Herbicide Resistance

By Mark Loux OSU Extension

We have been screening a random sample of waterhemp populations for herbicide resistance over the past two years.  Herbicides used in the screen include mesotrione, atrazine, 2,4-D, fomesafen, and metolachlor.  Results of our research show that it’s possible for Ohio waterhemp populations to have some level of resistance to one, several, or all of these herbicides.  Glyphosate is not included because we assume almost all populations are already resistant to this.  We are also part of a regional project that has been screening for dicamba and glufosinate resistance with populations that we supply, although none has been identified to date.  Our sample size has been small so far, so at this point we are looking to expand our screening to include waterhemp populations submitted by anyone in Ohio looking for more information about their response to herbicides.  It’s preferable to have seed from waterhemp plants that have survived POST herbicide treatments, or where it appears that preemergence herbicides were fairly ineffective, if possible.  But we will screen any populations provided within the constraints of time and greenhouse space.  For a quick reminder about how to tell when seed from waterhemp is mature, check out this video.  When seed is mature, you can cut off seedheads and place in an open paper bag until ready to get them to us.  Or just shake heads into some type of container to collect seed.  Send us an email and we will figure out the best way to get seed to us, or if you need more information.  loux.1@osu.edu

Also – a reminder that while we would like to have seed from surviving waterhemp plants, the most effective method of preventing future problems with this weed is to not let any go to seed.  Not only because plants that survive may have resistance, but because they produce gobs of seed that will result in misery the following year.  Removal of these plants should have high priority right now.  However, where it’s apparent that this is not going to happen for whatever reason, make a note of the infested fields, and check on them starting in a couple weeks for seed.  This should help us to get a better handle on how resistance in waterhemp is evolving.

Poison Hemlock is in Full Flower

By Joe Boggs – OSU Extension

Poison Hemlock is in Full Flower and Towering over Fields and Landscapes in Ohio.

Poison hemlock is one of the most lethal plants found in North America.  This biennial weed is now in full flower throughout much of Ohio.  So, the clock is ticking on preventing seed production by this non-native invasive plant.

As a biennial weed, poison hemlock spends the first year as a basal rosette and the second year as an erect, towering flowering plant that can measure 6-10′ tall.

Poison hemlock belongs to the carrot family, Apiaceae (formerly Umbelliferae).  It shares many characteristics with other notable non-native members of the carrot family found growing in Ohio such as Queen Anne’s Lace (Daucus carota) and Wild Parsnip (Pastinaca sativa).  Indeed, some of the accidental poisonings in the U.S. have occurred with people mistaking poison hemlock for Queen Anne’s Lace.

Poison hemlock contains highly toxic piperidine alkaloid compounds, including coniine and gamma-coniceine, which cause respiratory failure and death when ingested by mammals.  The roots are more toxic than the leaves and stems; however, all parts of the plant including the seeds should be considered dangerous.  It is a common misconception that poison hemlock sap will cause skin rashes and blisters.  In fact, poison hemlock toxins must be ingested or enter through the eyes, cuts, or other openings to cause poisoning.

All stages of the poison hemlock plant have bluish-green leaves that are 3-4 times pinnately compound, and the deeply cut parsley-like leaflets have sharp points.  Flowering plants have hairless, light-green to bluish-green stems that are covered with obvious purplish blotches.  Clusters of tiny white flowers are borne on structures called umbels that look like upside-down umbrellas.

While poison hemlock can be partially managed by mowing and tilling, the most effective control approach involves properly timed applications of selective or non-selective post-emergent herbicides including glyphosate (e.g. Roundup).  However, applications of herbicides must be made now to have any chance of reducing seed production this year.

Fall-Applied Herbicides: Odds and Ends

A commonly asked question about fall herbicides – how late in the fall can herbicides be applied and at what point is it too cold to apply?  We have applied well into December under some very cold conditions and still obtained effective control of winter annuals.  We suggest applying before Thanksgiving and aiming for a stretch of warmer weather if possible, but the effective treatments should work regardless.  Extended periods of freezing weather will cause the perennials to shut down – dandelion, thistle, dock.

We received a lot of questions about annual bluegrass this year, especially regarding difficulty in controlling it in the spring.  Fall is a good time to control this weed.  This will require the addition of glyphosate to whatever herbicide mix is being used. Continue reading Fall-Applied Herbicides: Odds and Ends →

Scout now for cressleaf groundsel in hayfields, or pay the price in May

By Mark Loux OSU Extension

Some hay producers have been unpleasantly surprised in the past when cressleaf groundsel infestations became evident in their hay fields in May prior to first cutting.  Cressleaf groundsel in hay or silage is toxic to animals, and infested areas of the field should not be harvested and fed.  Groundsel is a winter annual, emerging in late summer into fall, when it develops into a rosette that overwinters.  Growth restarts in spring, with stem elongation and an eventual height of up to several feet tall.  The weed becomes evident in hay fields when in becomes taller than the alfalfa/grass and develops bright yellow flowers in May.  The problem with passively waiting until this point to discover that the hay is infested with groundsel is that: 1) it’s too late to control it with herbicides; and 2) hay from infested areas has to be discarded instead of sold or fed, and large plant skeletons are still toxic even if herbicides were effective on them.  Groundsel plants finish their life cycle in late spring, once they flower and go to seed, so it should not be problem in subsequent cuttings.

Cressleaf Groundsel

The solution to this is scouting of hay fields in fall and early spring to determine the presence of cressleaf groundsel, when it is small and still susceptible to the few herbicides that can be used.  We expect groundsel to be more of a problem in new August seedings, since it would be emerging with the new stand of alfalfa/grass.  A well-managed established and uniform hay crop should be dense enough to largely prevent problems with winter annuals although there have been exceptions.  Groundsel will be most easily controlled in the fall while in the rosette stage.  Controlling plants in the spring is more difficult, because of cold conditions in early spring when plants are still small, and increased tolerance to herbicides as stems elongate.  Continue reading Scout now for cressleaf groundsel in hayfields, or pay the price in May →

Soil Residual Herbicides And Establishment Of Cover Crops In The Fall

By Marcelo Zimmer and Bill Johnson, Purdue Extension

Indiana growers have shown increased interest in utilizing cover crops in our corn and soybean production systems over the last decade.  Concurrently, there has also been increased utilization of soil residual herbicides to help manage herbicide-resistant weeds such as marestail (horseweed), waterhemp, and giant ragweed in our corn and soybean production systems.  Soil residual herbicides can remain active in the soil for a period of weeks to months after application.  The length of time a residual herbicide remains biologically active in the soil is influenced by soil texture, soil pH, organic matter, rainfall, and temperature.  Since these factors will vary from field to field, definitive time intervals of residual herbicide activity can be difficult to predict. Continue reading Soil Residual Herbicides And Establishment Of Cover Crops In The Fall →