Marestail – it’s everywhere

The photos of marestail here were taken in front of my house, along the intersection of the driveway and front walkway.    I have to suspect, given the proximity of these plants to where I exit the car every day, it’s likely that the marestail seed traveled with me from the OARDC Western Ag Research Station of another crop field.   I have found marestail all over Columbus, though, and there is plenty along the Scioto River which is just to the west of me.  So there is the possibility of seed traveling with prevailing weeds up the hill from the river.  So far the marestail around the house have been resistant to glyphosate, and my solution has been hand weeding and glufosinate (this allowed me to learn also that a high rate of glufosinate will kill lawn grasses).  One would think that resistance to glyphosate indicates the the seed came from an agricultural field rather than a native area, parkland, etc.  Recent work by a graduate student here at OSU compared the frequency of glyphosate resistance in marestail populations from north central Ohio with those from southern Iowa, and also compared populations from agricultural versus non-agricultural sites.  All of the populations from Ohio agricultural sites exhibited high level resistance, along with 60% of the populations from non-agricultural sites.   While over 90% of the Iowa populations from agricultural sites were resistant to glyphosate, the number with low versus high levels of resistance was fairly even.  And while 45% of the Iowa populations from non-agricultural sites were resistant to glyphosate, this occurred only at the lowest level of resistance for the majority.  In the end there can be plenty of glyphosate use and selection for resistance in both agricultural and non-agricultural areas, depending upon how they are managed.  Here in Ohio, it’s likely that a new infestation of marestail will be highly resistant to glyphosate, regardless of the seed source.  I suppose that cleaning my clothes and shoes well after working in marestail-infested areas could have prevented these plants in my driveway.  But I might have also needed a fine-meshed net on the west side of the house to prevent the influx of windborne seed.  Just some of the reasons why marestail remains enemy number one in soybeans.


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