Clethodim on brassicas, then rye

[Brian662]

Have some foxtail and witch grass starting in on my brassicas that are slow to fill in due to drought. Trying to maximize plot space, I normally overseed brassicas with rye. I've found the recommended plantback time on wheat/rye after a clethodim application is 30 days, is that everyone's experience as well? Would a lighter rate of clethodim cut that down? I still haven't applied extra urea to the brassicas because we haven't had a drop of rain in 24 days, but I'm afraid when I do the grasses will explode.

Any suggestions?

 

[Wind Gypsy]

Craig Harper's food plot book says clethodim doesn't have any soil residual for what that is worth.

I've got just one instance where i sprayed cleth and than broadcasted rye shortly after but there are too many other contributing factors that could have led to the poor results beyond the Cleth to glean much from it.

 

[FarmerDan]

Clethodim has no soil residual. It is rendered inert by soil microbes and water.

 

[Brian662]

That's interesting, nearly every thing I find online from multiple universities show 7 days to one month.

Screenshots below from
University Nebraska
University of Arkansas
Same information from Mississippi soy bean organizations, not pictured.

 

[FarmerDan]

I sometimes get a little cavalier. Soil persistence of contact herbicides never bothered me. But to be safe, safe, safe you are right to follow the label instructions.

A clethodim label will take the most conservative approach possible to avoid any remote liability or controversy.

I should have added this caveat. I look at everything as an event with a probability. Are there situations where my statement above will be wrong? Sure but I understand my soils, weather, and the action of the herbicides being used.

If you apply your herbicide at the appropriate rate -- and do not follow a 'more is better' thought process then the amount of herbicide persisting in the soil at its half life, to me, means it is ineffective.

https://files.dnr.state.mn.us/forestry/certification/pesticides/dnr-esra-clethodim.pdf

 

[Wild Thing]

Clethodim has no soil residual. It is rendered inert by soil microbes and water.

That was always my understanding as well Farmer Dan....until just recently. I guess it depends upon who/what you believe as to whether or not Clethodim has residual effects in the soil. As of this past week or two, I have now moved into the...."It definitely does have residual effects in the soil" group. Here is why:

This year I decided to terminate 3 small switchgrass plots and convert them back into food plots. I mowed them twice this summer (as a bonus - I used some of the thatch to mulch around some oak and crabapple seedlings and it worked great). On August 8th I sprayed the plots with Glyphosate in preparation for drilling my fall cover crop mix into these plots. A guy on the Michigan Sportsman Forum suggested that the Gly alone may not work as well as I might want it to and he suggested that I also spray the switchgrass with Clethodim just to make sure.... On August 12th, I sprayed all 3 plots with Clethodim/Crop Oil (16 oz & 1 Qt/acre).




On August 13th - the day after spraying the Clethodim, I drilled my fall cover crop which included mostly legumes and a heavy dose of cereal rye (100#/acre). We got some timely rains and my wife and I went on vacation out west to see some National Parks. You can imagine my dismay when we returned on September 4th to see this. I had almost zero germination of the rye seed.


This strip, adjacent to the switchgrass plot was drilled with the same mix on the same day and everything came up fine...


The near section of this plot had no switchgrass in it so I didn't spray it with Clethodim but I did spray the rest of the plot. That portion that had not been sprayed with Cleth germinated just fine...but I had zero gemination of rye in the portion of the plot which had been sprayed with Clethodim.


The other seeds in the mix all germinated just fine (peas, radish, vetch, clovers....but the rye never germinated. The only explanation I have for this phenomena is that the Clethodim did, in fact, have some residual effect in the soil.


Other plots where I drilled the same seed mix at the same depth a week or so later have all come up just fine. The only place where the rye failed to germinate was in those switchgrass plots where I had sprayed Clethodim the day before planting.









Here is what an article from the NDA had to say:

"Residual soil activity varies widely based on the herbicide, use rate, soil, and precipitation. Some herbicides have short residual activity, whereas others may remain active for many months. For example, clethodim is a grass-selective herbicide that remains active in the soil for approximately seven days."

Plant-Back Intervals Prevent Herbicide Trouble in Food PlotsNational Deer Associationhttps://deerassociation.com › plant-back-intervals

I hope the residual effect really does only last 7 days as I broadcasted 200# more of cereal rye in those plots yesterday (Sept 5th). Hopefully I will see it come up soon.

 

[omicron1792]

You know wild, I like to drill first, then spray. If you spray and drill you will push some thatch with chemicals down into the ground with the seed. If you drill first they will be covered and not be in contact with chemicals.

My guess is the chemicals slow the germination but don’t stop it. I bet the field will do just fine after a slower start.

Lots of data that gly affects seed germination, but only if in contact with the seed.

 

[omicron1792]

I sometimes get a little cavalier. Soil persistence of contact herbicides never bothered me. But to be safe, safe, safe you are right to follow the label instructions.

A clethodim label will take the most conservative approach possible to avoid any remote liability or controversy.

I should have added this caveat. I look at everything as an event with a probability. Are there situations where my statement above will be wrong? Sure but I understand my soils, weather, and the action of the herbicides being used.

If you apply your herbicide at the appropriate rate -- and do not follow a 'more is better' thought process then the amount of herbicide persisting in the soil at its half life, to me, means it is ineffective.

https://files.dnr.state.mn.us/forestry/certification/pesticides/dnr-esra-clethodim.pdf

View attachment 56839

You’re a wealth of info farmer. Thank you my man.

 

[Telemark]

That was always my understanding as well Farmer Dan....until just recently. I guess it depends upon who/what you believe as to whether or not Clethodim has residual effects in the soil. As of this past week or two, I have now moved into the...."It definitely does have residual effects in the soil" group. Here is why:

This year I decided to terminate 3 small switchgrass plots and convert them back into food plots. I mowed them twice this summer (as a bonus - I used some of the thatch to mulch around some oak and crabapple seedlings and it worked great). On August 8th I sprayed the plots with Glyphosate in preparation for drilling my fall cover crop mix into these plots. A guy on the Michigan Sportsman Forum suggested that the Gly alone may not work as well as I might want it to and he suggested that I also spray the switchgrass with Clethodim just to make sure.... On August 12th, I sprayed all 3 plots with Clethodim/Crop Oil (16 oz & 1 Qt/acre).
View attachment 56858

View attachment 56859

On August 13th - the day after spraying the Clethodim, I drilled my fall cover crop which included mostly legumes and a heavy dose of cereal rye (100#/acre). We got some timely rains and my wife and I went on vacation out west to see some National Parks. You can imagine my dismay when we returned on September 4th to see this. I had almost zero germination of the rye seed.
View attachment 56860

This strip, adjacent to the switchgrass plot was drilled with the same mix on the same day and everything came up fine...
View attachment 56861

The near section of this plot had no switchgrass in it so I didn't spray it with Clethodim but I did spray the rest of the plot. That portion that had not been sprayed with Cleth germinated just fine...but I had zero gemination of rye in the portion of the plot which had been sprayed with Clethodim.
View attachment 56862

The other seeds in the mix all germinated just fine (peas, radish, vetch, clovers....but the rye never germinated. The only explanation I have for this phenomena is that the Clethodim did, in fact, have some residual effect in the soil.
View attachment 56863

Other plots where I drilled the same seed mix at the same depth a week or so later have all come up just fine. The only place where the rye failed to germinate was in those switchgrass plots where I had sprayed Clethodim the day before planting.

View attachment 56865

View attachment 56866

View attachment 56867

View attachment 56868

Here is what an article from the NDA had to say:

"Residual soil activity varies widely based on the herbicide, use rate, soil, and precipitation. Some herbicides have short residual activity, whereas others may remain active for many months. For example, clethodim is a grass-selective herbicide that remains active in the soil for approximately seven days."

Plant-Back Intervals Prevent Herbicide Trouble in Food PlotsNational Deer Associationhttps://deerassociation.com › plant-back-intervals

I hope the residual effect really does only last 7 days as I broadcasted 200# more of cereal rye in those plots yesterday (Sept 5th). Hopefully I will see it come up soon.

That may have been at least partially due to the use of the oil. The herbicide would definitely behave differently in oil than in water, almost certainly making it more persistent.

 

[Wild Thing]

You know wild, I like to drill first, then spray. If you spray and drill you will push some thatch with chemicals down into the ground with the seed. If you drill first they will be covered and not be in contact with chemicals.

My guess is the chemicals slow the germination but don’t stop it. I bet the field will do just fine after a slower start.

Lots of data that gly affects seed germination, but only if in contact with the seed.

I have planted both ways many times in the past - drill first - then spray .... spray first - then drill. Both ways have always worked out well for me. It wasn't until a year or so ago when I saw the video of the guy spraying the seed laying on top of the soil with Gly and then having very dismal results that I decided from here on I will spray first and plant later. This has always worked out well for me.

Virtually ALL of the other plots I have planted over the years where I sprayed first and and then planted later have had optimal germination. The only time I have experienced a failure was this year in the switchgrass plots where I sprayed Clethodim first and planted later. Of course....I think this is the first time I have ever followed a Clethodim treatment with a grass planting. I have always just used Clethodim to treat grasses in alfalfa, clovers, etc.

 

[omicron1792]

I have planted both ways many times in the past - drill first - then spray .... spray first - then drill. Both ways have always worked out well for me. It wasn't until a year or so ago when I saw the video of the guy spraying the seed laying on top of the soil with Gly and then having very dismal results that I decided from here on I will spray first and plant later. This has always worked out well for me.

Virtually ALL of the other plots I have planted over the years and then planted later have had optimal germination. The only time I have experienced a failure was this year in the switchgrass plots where I sprayed Clethodim first and planted later. Of course....I think this is the first time I have ever followed a Clethodim treatment with a grass planting. I have always just used Clethodim to treat grasses in alfalfa, clovers, etc.

I think If you spray and plant a couple of days later that’s fine. I read it as you planted same day. That’s just been my experience.

Broadcast and spray after does worse in my opinion. Drill buries most of seed. Spray away!

 

[omicron1792]

That may have been at least partially due to the use of the oil. The herbicide would definitely behave differently in oil than in water, almost certainly making it more persistent.

I think this is true! As farmer said cleth/gly have to contact soil to go inert. Corp oil prob kept some in suspension and active.

 

[Wild Thing]

I think If you spray and plant a couple of days later that’s fine. I read it as you planted same day. That’s just been my experience.

Broadcast and spray after does worse in my opinion. Drill buries most of seed. Spray away!

Nope - I sprayed on August 12th and drilled the seed on August 13th - the following day.

 

[Brian662]

I have read other accounts of people that have had results similar to WildThing with this same scenario. I guess moral of the story is buyer beware, under certain conditions you may experience a residual that negatively effects germination.
My plan will be to spray the cleth and wait at least a week before broadcasting seed. With the lack of rain we've had, it may not matter anyways.

 

[FarmerDan]

I have planted both ways many times in the past - drill first - then spray .... spray first - then drill. Both ways have always worked out well for me. It wasn't until a year or so ago when I saw the video of the guy spraying the seed laying on top of the soil with Gly and then having very dismal results that I decided from here on I will spray first and plant later. This has always worked out well for me.

Virtually ALL of the other plots I have planted over the years where I sprayed first and and then planted later have had optimal germination. The only time I have experienced a failure was this year in the switchgrass plots where I sprayed Clethodim first and planted later. Of course....I think this is the first time I have ever followed a Clethodim treatment with a grass planting. I have always just used Clethodim to treat grasses in alfalfa, clovers, etc.

I am humbled....

 

[Brian662]

I think this is true! As farmer said cleth/gly have to contact soil to go inert. Corp oil prob kept some in suspension and active.

But the label says to use cleth with oil, so isn't that a moot point?
If you can't get the cleth to do its job without crop oil, you may as well not use it. If there is a soil residual from crop oil or the cleth, when used as directed, then isn't it cause for concern?

 

[omicron1792]

But the label says to use cleth with oil, so isn't that a moot point?
If you can't get the cleth to do its job without crop oil, you may as well not use it. If there is a soil residual from crop oil or the cleth, when used as directed, then isn't it cause for concern?

I like water based NIS better. Maybe a little less effective but have never had that issue.

 

[omicron1792]

But the label says to use cleth with oil, so isn't that a moot point?
If you can't get the cleth to do its job without crop oil, you may as well not use it. If there is a soil residual from crop oil or the cleth, when used as directed, then isn't it cause for concern?

Most say use crop oil or NIS, with crop oil being a bit more effective.

https://www3.epa.gov/pesticides/chem_search/ppls/042750-00072-20200520.pdf

 

[Wild Thing]

I am humbled....

LOL - Not trying to humble or prove you wrong at all Farmer Dan. I know you have much more experience in this business than I do for sure. Truthfully, I had never even given a thought to whether or not there was any residual with Clethodim as I have always used it for maintenance in broadleaf plots. I am sure this was the first time I have ever followed a Clethodim spraying with a grass planting. My experience with the rye failing to geminate after spraying the switchgrass with Cleth was very enlightening for sure.

It is a time-tested fact.....that you do learn something new every day (or maybe at least every year). I know I do for sure.