Weeds

C.O.R.N. Newsletter Articles

  1. Canada thistle rebounds?

    Author(s): Mark Loux

    It can be nice to see old friends.  Except when they cause crop and yield loss, refuse to leave after a few days, and don’t respond to chemicals.  A while back we wrote about what appeared to be an increase in populations of dandelions and other winter weeds and made some guesses about why this was happening.  Canada thistle has once again become a problem in some fields in a big way, probably for some of the same reaso

    Issue: 2021-19
  2. Poison hemlock (Conium maculatum L.) and wild parsnip (Pastinaca sativa L.) are combined in this report because these invasive non-native weeds are increasingly found growing together in Ohio. However, the defense chemicals of these weeds are very different and have vastly different modes of action. This is important to understand relative to management options as well as medical treatments for exposure to these highly dangerous weeds.

    Putting poison hemlock in perspective

    Author(s): Mark Loux , Author(s): Ted Wiseman , Author(s): Allen Gahler

    Wild Parsnip FlowersPoison hemlock seems to be on everyone’s radar more than usual this year, especially in northern Ohio.  We know that while hemlock has been all over southern Ohio for years, it is continuing to spread northward, where new occurrences and observations of it may be engendering concern in the general public and local government. There have also been comments that it seems “worse than usual” this year in

    Issue: 2021-19

  3. Roughstalk Bluegrass in Cereal Grain and Forage Crops

    Author(s): Richard Purdin , Author(s): Taylor Dill , Author(s): Les Ober, CCA

    Roughstalk BluegrassThere is a new and emerging weed challenging cereal grain and forage producers across the state. Roughstalk Bluegrass has taken root in wheat fields and newly established forage stands. This weed has reached population levels high enough to inhibit the harvest of cereal grains, reduce the quality of forages, and crowd out newly established forages.

    What is it?

    Issue: 2021-18

  4. Distribution of waterhemp and Palmer amaranth in Ohio

    Author(s): Mark Loux

    The maps that accompany this article show our current knowledge of waterhemp and Palmer amaranth distribution in Ohio.  These are based on information from a survey of OSU Extension County Educators, along with information we had from samples submitted, direct contacts, etc.  We still consider any new introductions of Palmer amaranth to be from an external source (brought in from outside Ohio) – hay or feed, infested equipment, CRP/cover/wildlife seedings.  Palmer is not really spreading around the state, and as the map shows, we have had a number of introductions that were immediately reme

    Issue: 2020-18

  5. It’s All About the Weed Seedbank – Part 2: Where Has All the Waterhemp Come From?

    Author(s): Mark Loux

    Weed populations are constantly shifting, in response to the pressure from our cultural and herbicide use practices, and how good our management of weeds is (or isn’t).  Two weeks ago in CORN, we wrote about the apparent decline in marestail in parts of the state, although in subsequent communication we heard fairly clearly that not everyone’s populations had declined yet.  And there is bad news - waterhemp is spreading at a rapid rate, and it’s a considerably more challenging pest than marestail for several reasons.  The question really is – why has waterhemp taken off over the past severa

    Issue: 2019-12
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Publications

  1. Ohio, Indiana and Illinois Weed Control Guide, Bulletin 789
    12/2020

    Ohio, Indiana and Illinois Weed Control Guide, Bulletin 789. Publication gives detailed guidance on weed control selections. Numerous tables by crop and application help producers select the best product option for their weed control situation. Hard copy and PDF available for purchase

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