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 on 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. 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 – email@example.com, 614-395-2440. Thanks in advance for your help.
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