By Mark Sulc, OSU
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 hayfields when it 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 a problem in subsequent cuttings. Continue reading
By Mark Loux, OSU
Herbicide options for burndown of existing weeds prior to planting of no-till wheat include glyphosate, Gramoxone, Sharpen, and dicamba. Among these, the combination of glyphosate and Sharpen probably provides the best combination of efficacy on marestail, flexibility in application timing, and residual control. Dicamba labels have the following restriction on preplant applications – “allow 10 days between application and planting for each 0.25 lb ai/A used”. A rate of 0.5 lb ai/A would therefore need to be applied at least 20 days before planting. We do not know of any 2,4-D product labels that support the use of 2,4-D prior to or at the time wheat planting. There is some risk of stand reduction and injury to wheat from applications of 2,4-D too close to the time of planting. Liberty and other glufosinate products are also not labeled for use as a burndown treatment for wheat. Sharpen should provide limited residual control of winter annuals that emerge after herbicide application, and the rate can be increased from 1 to 2 oz/A to improve the length of residual. Gramoxone should also effectively control small seedlings of marestail and other winter annuals. Be sure to use the appropriate adjuvants with any of these, and increase spray volume to 15 to 20 GPA to ensure adequate coverage with Sharpen or Gramoxone.
There are several effective postemergence herbicide treatments for wheat that can be applied in November to control these weeds, in fields where preplant burndown treatments are not used. The most effective postemergence treatments include Huskie, Quelex, or mixtures of dicamba with either Peak, tribenuron (Express, etc), or a tribenuron/thifensulfuron premix (Harmony Xtra, etc). We discourage the application of 2,4-D to emerged wheat in the fall due to the risk of injury and yield reduction.
Fall herbicide treatments have fallen off over the past several years for a couple of reasons, among them the effectiveness of new soybean trait systems for managing marestail, some generally crappy weather in late fall, and efforts to reduce input costs. We are seeing a resurgence in some weeds, such as dandelion, which respond well to fall herbicides, though. Some growers have also experienced issues with messy fields and late spring burndowns that could have been avoided with fall herbicides. It’s worth recalling the history of fall herbicide applications, which helps explain some of their benefits, especially if you have not been managing weeds or making recommendations for as long as some of us have. Continue reading
By Mark Loux OSU Extension
In our windshield scouting of soybeans this year we have seen a lot of weed-free fields. This makes sense given the shift toward Xtend, LibertyLink, LLGT27, and Enlist soybeans over the past several years, which provides us with effective POST options for our major weed problems – common and giant ragweed, marestail, and waterhemp (now if we could just get rid of the baggage some of these traits carry). We are however getting many reports of late-season waterhemp as it grows through the soybeans and becomes evident. This also makes sense given that statewide we are in the midst of an overall increase in waterhemp, and continue to move up the curve in terms of the number of fields infested and the size of the infestations. Prevention and management of waterhemp and Palmer amaranth has been one of the primary goals of our state and county educational programs for half a decade or more. And one of the most important points about waterhemp and Palmer that we try to get across is their capacity for prodigious seed production – 500,000 to upwards of a million seeds per plant – and what this means for their ability to rapidly ramp up populations, infest equipment, etc. Continue reading
Common waterhemp true leaves without singular hair in the leaf tip notch
OSU weed scientists and ag engineers are looking for soybean fields that have populations of waterhemp or Palmer amaranth surviving into July and August (after all control with herbicides has been attempted). We have a project involving the use of a drone to identify these weeds in mid to late season when they are evident above the soybean canopy. We need fields with more than just a few surviving plants. Populations consisting of a few good patches up though a disaster are fine. Contact Mark Loux – firstname.lastname@example.org, 614-395-2440. Thanks in advance for your help.
There was a great deal of action last Friday in the case that vacated the registrations of XtendiMax, Engenia, and FeXapan dicamba-based products. Despite a barrage of court filings on Friday, however, nothing has changed the current legal status of the dicamba products in Ohio, and Ohio growers may use existing stocks of the products now. Still, they must end-use by June 30th, 2020.
Here’s a rundown of the orders that the Ninth Circuit Court of Appeals issued in the case last Friday:
The court denied the emergency motion that the petitioners (National Family Farm Coalition, Center for Food Safety, Center for Biological Diversity, and Pesticide Action Network North America) filed on June 13th. That motion asked the court to enforce its previous mandate to vacate the registrations, to prevent any further use of the products, and to hold the EPA in contempt for issuing the Cancellation Order the agency had made that allowed continued use of existing stocks of the products. The court did not provide its reasoning for denying the motion. Continue reading
By: Mark Loux and Bruce Ackley, OSU Extension
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 remediated. The number of counties where an infestation(s) is being managed is still low, and within those counties, the outbreak occurs in only a few fields still. Waterhemp is much more widespread in Ohio and is spreading rapidly within the state from existing infestations to new areas via equipment, water, animals, etc. We do not have Ag Educators in all counties, and even where we do, infestations can occur without us knowing about them. Feel free to contact us with new information to update the maps. Continue reading
By: Alyssa Essman and Mark Loux, Ohio State University Extension, Weed Science Specialist
The 2019 growing season came and went and left many fields in a state of disarray heading into 2020. Many growers that were unable to plant decided to use cover crops, to reduce soil erosion and provide some weed suppression during the extended fallow period. Terminating these cover crops using the right methods at the right time will be critical to ensure timely planting and prevent the cover crops from competing with cash crops. The three main methods of cover crop termination are natural (species that winter kill), chemical, and mechanical. Cover crops may also be bailed, grazed, or harvested as silage. Most species require some sort of management decision for termination. Cover crop species, growth stage, weather, and cover cropping goals should all be considered when planning termination method and timing. These decisions require a balance between growing the cover long enough to maximize benefits and terminating in time to prevent potential penalties to the following cash crop. Continue reading
By: Harold Watters, OSU Extension Ag Crops Field Specialist
Our OSU Extension AgNR educators observed soybean fields across the state again this fall to see what was out there for our annual fall soybean weed survey. I was supposed to share this early enough so you could at least get a fall application on to get a head start on controlling marestail, but it seems we have more problems than that to deal with.
Statewide our most frequently observed weed problem was again marestail. It was present in 36% of the fields. The second most likely observation was weed-free — at 29% of the fields. That’s a big jump over several years ago, and likely due to LibertyLink, Enlist, and Extend soybeans. Third, fourth and fifth places in a three-way tie were giant ragweed, volunteer corn and then giant foxtail (or just generic grass) — all in about 19% of the fields. Next, and getting ever more widespread, is waterhemp at 15% of the fields across the state. Continue reading