Noxious Weeds

Poison Hemlock and Wild Parsnip are Blooming in Southern Ohio

 

Originally posted on Buckeye Yard and Garden Online

By Joe Boggs- June 3, 2020

Poison hemlock (Conium maculatum) and wild parsnip (Pastinaca sativa) are two of our nastiest non-native weeds found in Ohio.  Poison hemlock is one of the deadliest plants in North America.  Wild parsnip can produce severe, painful blistering.  Both are commonly found growing together.

Poison hemlock and wild parsnip are members of the carrot family, Apiaceae.  The old name for the family was Umbelliferae which refers to the umbel flowers.  They are a key family feature with short flower stalks rising from a common point like the ribs on an umbrella.

Continue reading Poison Hemlock and Wild Parsnip are Blooming in Southern Ohio →

Omitting residual herbicides in soybeans – really – we have to have this argument again?

Source: Dr Mark Loux, OSU Extension

According to our network of sources, the effectiveness of new soybean trait systems has some growers once again thinking about omitting preemergence residual herbicides from their weed management programs.  Some people apparently need to learn the same lessons over and over again.  Having gone through this once in the early 2000’s when Roundup Ready soybeans had taken over and we all sprayed only glyphosate all day every day, we think we’re pretty sure where it leads.  We’re sensitive to concerns about the cost of production, but the cost-benefit analysis for residual herbicides is way in the positive column.  We’re not the ones who ultimately have to convince growers to keep using residual herbicides, and we respect those of you who do have to fight this battle.  Back in the first round of this when we were advocating for use of residuals, while the developers of RR soybeans were undermining us and telling everyone that residuals would reduce yield etc, we used to have people tell us “My agronomist/salesman is recommending that I use residuals, but I think he/she is just trying to get more money out of me”.  Our response at that time of course was “no pretty sure he/she is just trying save your **** and make sure you control your weeds so that your whole farm isn’t one big infestation of glyphosate-resistant marestail.”  And that answer probably works today too – maybe substituting waterhemp for marestail.

We need to state here that a good number of growers kept residual herbicides in their programs through all of this, and we assume they aren’t tempted to omit them now either.  For everyone else – maybe interventions are called for.  Where the recalcitrant person is repeatedly thumped with a stick while being reminded of what happened last time, until they change their minds.

Weed scientist:  so you’re going to use residual herbicides right?

Soybean grower:  no

Thump

WS:  remember what happened last time – lambsquarters became a problem when every residual herbicide would have controlled it.  Change your mind yet?

SB:  no

Thump

WS:  remember when the weather didn’t cooperate and you ended up spraying 2 foot tall weeds because of no initial control?  Do you want this again?

SG:  no

WS:  so you’re going to use residuals?

SG:  not sure

Thump

WS:  and you expect your local dealer to clean up whatever mess occurs when you don’t use residuals?

SG: yes

Thump

WS:  remember when you burnt out the FirstRate on marestail and then the glyphosate wouldn’t work?  Do you want this to happen with dicamba, 2,4-D and glufosinate?”

SG:  no

WS:  well then

SG:  maybe

Gentler persuasive tap

WS:  You know how bad a weed waterhemp is right?

SG:  yes

WS:  what if residuals will help prevent waterhemp infestations

SG:  Ok then – yes

WS:  ok then

Note:  we considered a number of sound effects here – thump, zap, whack…. Thump won out for no particular reason.  We could not decide whether getting hit by a stick was more or less acceptable than getting shocked in this context.

The bottom line is that residual herbicides provide both short- and long-term risk management in weed management for a relatively low cost.  A non-inclusive list of these:

– reduces weed populations overall and slows weed growth, resulting in more flexibility in the POST application window.

– Reduced risk of yield loss if weather interferes with timely POST application.  In the absence of residual herbicides, soybean yield loss can occur when weeds reach a height of 6 inches.

– increases the number of different sites of action used within a season, slowing the rate of resistance development

– reduces the number of weeds that are treated by POST herbicides, which also slows the rate of herbicide resistance development

– residuals control lambsquarters which is not well-controlled by POST herbicides

– the most significant weed problems in Ohio soybean production – waterhemp, giant ragweed, and marestail – cannot be consistently controlled with POST herbicides alone.  They require a comprehensive herbicide program that includes residual and POST herbicides.  It may be possible to make a total POST system work some years or for a while, but in the end this approach will result in problems with control and speed up the development of resistance.

This whole subject of omitting residual herbicides makes us cranky because we don’t have to guess what will happen.  We’ve made our best case here.  It’s up to you of course, but we suggest that we not have to come back and have this discussion again.  Because next time we’re bringing a few friends, a bigger stick, and a gorilla.

Disclaimer:  Parts of this article are meant in pure jest.  We would certainly never advocate in earnest the use of physical harm or other methods of persuasion to change the behavior of herbicide users.  This goes against everything that the discipline of weed science stands for, and also OSU.  Plus – we don’t even know where to rent a gorilla.

 

No Pigweed Left Behind – Late-Season Scouting for Palmer Amaranth and Waterhemp

Source: Dr. Mark Loux (edited)

Remain vigilant!  We have Palmer and Waterhemp in Knox County!! Now is an excellent time to scout for these weeds, especially in bean fields. If you would like help with identification call John at 740-397-0401.

If you don’t already have to deal with waterhemp or Palmer amaranth, you don’t want it.  Ask anyone who does.  Neither one of these weeds is easy to manage, and both can cause substantial increases in the cost of herbicide programs, which have to be constantly changed to account for the multiple resistance that will develop over time (not “can”, “will”).  The trend across the country is for Palmer and waterhemp to develop resistance to any new herbicide sites of action that are used in POST treatments within about three cycles of use.  Preventing new infestations of these weeds should be of high priority for Ohio growers.  When not adequately controlled, Palmer amaranth can take over a field faster than any other annual weed we deal with, and waterhemp is a close second.  Taking the time to find and remove any Palmer and waterhemp plants from fields in late-season before they produce seed will go a long way toward maintaining the profitability of Ohio farm operations.  There is information on Palmer amaranth and waterhemp identification on most university websites, including ours –  u.osu.edu/osuweeds/ (go to “weeds” and then “Palmer amaranth”).  An excellent brief video on identification can be found there, along with an ID fact sheet.  The dead giveaway for Palmer amaranth as we move into late summer is the long seedhead, and those on female seed-bearing plants are extremely rough to the touch.  We recommend the following as we progress from now through crop harvest: Continue reading No Pigweed Left Behind – Late-Season Scouting for Palmer Amaranth and Waterhemp →

The Ohio Noxious Weed Law – A Tool in the Prevention of Waterhemp and Palmer Amaranth

Source: Dr. Mark Loux

Waterhemp and Palmer amaranth are both now listed on the Ohio noxious weed law, which means that landowners must take steps to control infestations and prevent further spread.  Since these are annual weeds, preventing spread is achieved by preventing plants from reaching maturity and producing seed.  This is the basis for our “No pigweed left behind” effort, for which the goal is to create an understanding that the only way to beat these weeds is to prevent seed.  Prevention needs to occur in any area that might be subject to infestation, such as roadsides, parks, conservation seedings, parks, etc, in addition to agricultural fields.  The entities managing these areas are responsible for recognizing and controlling infestations of waterhemp and Palmer amaranth, but this does not always occur.  Not everyone involved in crop production or land management is aware of the waterhemp/Palmer problem to begin with, and many managers are busy enough that preventing noxious weed problems has low priority.

Our advice is to pay attention to what’s happening in your area or in the areas that you farm, with the goal of becoming aware of new infestations early enough that plant maturity and seed can still be prevented, regardless of where they may be occurring.  We recommend as a first step contacting the land manager or owner to explain the issue, make them aware that they have an infestation, and request that action be taken.  However, where it’s not possible to have this conversation, or there is a refusal to take action, the Ohio noxious weed law can be used to try to force action.  A two-page summary of the noxious weed law that can be found here on the OSU Ag Law Blog, and also links directly to the law itself.

The basic idea here is that following an unsuccessful attempt to work with a landowner or manager, noxious weed issues should be reported to township trustees, and this must be done in writing.  The trustees then have the responsibility to deal with the issue, and the method for doing so varies depending upon what the land is used for and who is managing it.  If it’s necessary to use the noxious weed law, be sure to start the process early enough in summer, well before potential seed production.  There is a need to allow time for all of the steps in the process to occur, and for notifications to be received and acted on (or not).  Our experience is that not all landowners and managers will take action upon first notification, and in addition to action, their response to notification can include minimal response of protesting their need to act.  Waiting too late to start the process can result in lack of resolution of these issues in time to prevent plant maturity and seed production.  The noxious weed law has been used several times within the last two years to force managers to control Palmer amaranth, and could be used to accomplish the same for waterhemp, which was recently added to the list.  Consider the law a tool to prevent the establishment and spread of these weeds when other methods are ineffective.

You can search this blog for a complete description and pictures of all the weeds on the Ohio Noxious weed list.

No pigweed left behind

No pigweed left behind

Noxious Weeds in Cover Crop Seed and Seed Germination

Source: Alexander Lindsey, Laura Lindsey, Mark Loux, Anne Dorrance, Stan Smith, John Armstrong, OSU Extension

Seed quality is key to establishing a good crop (or cover crop). Some of the critical components of seed quality are percent germination, mechanical analysis for purity (% other crops, % inert, and % weeds), and a listing of noxious weeds identified by scientific/common name and quantity found. As producers are looking for seed sources to provide living cover on acreage this year that was previously earmarked for corn or soybeans, it is important to pay attention to the quality. These tests may also be required on seed lots for use in some relief programs as well. Commercial or certified seed used for cover crops should have a seed tag that shows variety and the seed quality measurements above. However, if the seed is sourced from out of state, the noxious weeds listed (or NOT listed) on the tag by name may differ from those had the seed been sourced from Ohio.

Only the noxious weeds for the state where the seed was originally going to be sold are required to be listed on the tag by name and quantity (Federal Seed Act, part 201.16). Each state determines which species are included on this list, and can differ from state to state. If seed is outside of Ohio for use on-farm, producers may want to have the seed tested for an “all state noxious-weed exam” prior to planting if this was not done previously on the seed lot. Only 1.1-1.2 lbs of seed is needed for the test, but it is critical the sample is representative of the lot to ensure quality test results. This test would screen the seed sample supplied for the weed contained in this list: https://www.ams.usda.gov/sites/default/files/media/StateNoxiousWeedsSeedList.pdf, and may serve as a more comprehensive exam than was conducted at the time of initial seed lot labeling. One service provider that can conduct this exam is Central Ohio Seed Testing (a subsidiary of the Ohio Seed Improvement Association; https://ohseed1.org/about-our-lab/). Samples can also be sent to ODA for an Ohio noxious weed exam (https://agri.ohio.gov/wps/portal/gov/oda/divisions/plant-health/grain-warehouse-feed-and-seed/). Depending on the source of seed and the planned use, a seed lot may be eligible to be tested for free through ODA between June and December (up to three per farmer). Conducting a noxious weed exam could help slow the movement of problematic weeds throughout the state and minimize future weed problems.

Another issue to consider is the quality of seed in storage that was not planted this year due to weather. Storing seed in an environment where the temperature (in F) plus the % relative humidity are less than 100 (Harrington’s rule) helps to minimize the rate of seed deterioration (or loss in germination and vigor). Seed germination is an important consideration for determining seeding rate to ensure the critical final stand for yield is achieved for crops like corn and soybeans. Most seed germination percentages on a seed tag for agricultural seeds (like corn and soybeans) are valid for 12 months from the last date of the month in which they were completed, with the exception being cool season grasses which are valid for 15 months beyond the month of testing (Ohio Revised Code, Chapter 907.07). Be sure to check the seed tag for both the date of the test as well as the germination when planning seeding rates.

You can search this blog for a complete description and pictures of all of the weeds on the Ohio Noxious weed list.

It’s All About the Weed Seedbank – Part 1: Where Has All the Marestail Gone?

Source: Mark Loux

For the second year in a row, we are scrounging to find enough marestail at the OARDC Western Ag Station to conduct the research we had planned on this weed.  After years of having plenty of marestail, we have had to look around for off-site fields where there is still a high enough population.  Which, since we are scientists after all, or at least make our best attempts, left us thinking about reasons for the lack of marestail, and our overall marestail situation, and seedbanks.

While the short game in weed management is about getting good enough control to prevent weeds from being a yield-limiting factor and interfering with harvest, the long game is about preventing seed production and managing the soil seedbank.  One of the characteristics shared by marestail, giant ragweed, and the nasty pigweeds, waterhemp and Palmer amaranth, is a rapid decline in seed viability in the soil within the first year, and an overall decline to 5% or less viable seed within 3 to 4 years.  Another characteristic of marestail and pigweed seed is a relative lack of dormancy, which results in the potential for an almost immediate increase in population the year following a year of substantial escapes and seed production.  How big that increase is depends upon how many plants go to seed and how many seeds are produced per plant, with the potential of up to about 200,000 seeds per marestail plant and one million per waterhemp or Palmer amaranth plant.  The net result of these two characteristics, though, is that these weeds can ramp up population fast following a year of poor control, but populations can also decline rapidly with good control that prevents seed.

Continue reading It’s All About the Weed Seedbank – Part 1: Where Has All the Marestail Gone? →

The LL-GT27 soybean – what’s legal?

Source: Dr. Mark Loux, OSU Extension

We are starting to see the availability of soybean varieties with more than two herbicide resistance traits, which can expand the herbicide options, improve control, and allow multiple site of action tank mixes that reduce the rate of selection for resistance.  One of these is the Enlist soybean, with resistance to glyphosate, glufosinate, and 2,4-D.  As of this writing, full approval for the Enlist soybean is still being held up by the Philippines (because they can apparently).  The other is the LL-GT27 soybean, which has resistance to glyphosate, glufosinate, and isoxaflutole (Balance).  There is no label for use of isoxaflutole on this soybean yet, but it is legal to apply both glyphosate and glufosinate.  In Ohio, as long as neither label prohibits applying a mixture of two herbicides labeled for a specific use, it’s legal to apply the mixture.  So, it’s also legal to apply a mixture of glyphosate and glufosinate to the LL-GT27 soybean.  There is no label that actually mentions or provides guidance for this mixture, which does not affect legality, but could affect who assumes liability for the recommendation to apply a mixture if that matters to you.  Some seed companies are making the recommendation for POST application of the mix of glyphosate and glufosinate to the LL-GT27 soybean in printed materials.  Our interpretation after discussion with ODA, is that these materials are essentially supplements to labels, and so the seed company would assume some liability for the recommendation.

Continue reading The LL-GT27 soybean – what’s legal? →

Changes Made to Ohio’s Prohibited Noxious Weeds List

Source: Peggy Kirk Hall, Associate Professor, Agricultural & Resource Law (edited)

Palmer Amaranth

New changes to Ohio’s prohibited noxious weeds list took effect Friday, September 14th.  The Ohio Department of Agriculture (ODA) added 13 new species to the list, and removed 3 species.

On this blog, throughout the spring and summer I posted information and identification tips on each of the 21 Ohio noxious weeds.  This information can be easily found by typing “noxious weeds” in the Search this blog… box found on any page within our blog.  In the upcoming weeks, I will add similar posts for each of the new weeds added to this list.

Added to the list of prohibited noxious weeds are:

  • Yellow Groove Bamboo (Phyllostachys aureasculata), when the plant has spread from its original premise of planting and is not being maintained.
  • Field bindweed (Convolvulus arvensis).
  • Heart-podded hoary cress (Lepidium draba sub. draba).
  • Hairy whitetop or ballcress (Lepidium appelianum).
  • Perennial sowthistle (Sonchus arvensis).
  • Russian knapweed (Acroptilon repens).
  • Leafy spurge (Euphorbia esula).
  • Hedge bindweed (Calystegia sepium).
  • Serrated tussock (Nassella trichotoma).
  • Columbus grass (Sorghum x almum).
  • Musk thistle (Carduus nutans).
  • Forage Kochia (Bassia prostrata).
  • Water Hemp (Amaranthus tuberculatus).

Removed from the list are:

  • Wild carrot (Queen Anne’s lace) (Daucus carota L.).
  • Oxeye daisy (Chrysanthermum leucanthemum var. pinnatifidum).
  • Wild mustard (Brassica kaber var. pinnatifida).

Continue reading Changes Made to Ohio’s Prohibited Noxious Weeds List →

Harvest Considerations to Reduce Weed Seed Movement

Source: Iowa State University Extension

Weed seed spread by a combine

Harvest is just around the corner for many Iowa farmers and now is a good time to consider options to reduce movement of weed seed between fields with harvest equipment. While we may not think of it during harvest time, combines are extremely effective at transporting seed from field to field. A few precautions leading up to harvest and during harvest can help manage any escaped problem weeds.

Prior to harvest, scout fields for escaped weeds since weeds are easier to see after crops have matured. This is important to identify problem fields or areas for next year. Your notes about weed problems are critical to choosing effective management tactics for next year, so make this a priority prior to harvest. In some situations scattered weeds could be removed from the fields prior to harvest. It is much easier to manage weed issues before they drop mature seed or before that mature seed goes through a combine.

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