Will blackgrass seed be viable if sprayed now?

[Tractor Boy]

I have some stubbles that are due to be spring cropped. I was hoping to only use a dose of glyphosate in the spring pre drilling but have been scuppered.
Basically although there were no viable seed heads in the crop harvested in August there must have been some blackgrass in the bottom that has over the past month put heads up. I sprayed some yesterday and have some more to do with 4L/ha 360 glypho. Some of the heads are massive, some are flowering, although some have either not started flowering or have finished but the heads are still green. Will the glyphosate render all the seed unviable?
Some of these are after a spring cereal or linseed and are due to go another spring crop.

 

[Oat]

If some are flowering, then other seeds on the head are probably already viable and/or will be before any glyphosate has a chance to act

 

[deleted user 837354]

If some are flowering, then other seeds on the head are probably already viable and/or will be before any glyphosate has a chance to act

I agree. Knowing my luck they will be unaffected by the glyphosate.

 

[Oat]

I agree. Knowing my luck they will be unaffected by the glyphosate.

Only if you have been recommending repeated low rates and have bred resistance

 

[Kingcj]

Is it too wet to cultivate? A shallow pass would give it a headache and encourage others to germinate in spring when it warms up before you drill it?

 

[yellow belly]

Glyphosate should stop seeds 2 weeks after flowering it takes 2 weeks for the seeds to be viable after fertilisation

Test the seed by squeezing it and if it is watery ripe then it may be viable

We had some rape fields that were unsprayed at harvest which had some bg heads that were flowering when we drillied wheat in early October and then treated with glyphosate the heads we checked last week had no viable seeds when you squeeze the head it feels empty

Bg may produce a lot of seeds more than 50% are normally unviable

This time of year flowering bg may not fertilise because of low light levels and low temperature

My son did his degree dissertation on black grass and studied many of the scientific papers on black grass written over the last 30 years

 

[Tractor Boy]

Is it too wet to cultivate? A shallow pass would give it a headache and encourage others to germinate in spring when it warms up before you drill it?

I use a no til drill, and don’t really have a shallow stubble cultivator even if I wanted to use one.

 

[yellow belly]

Is it too wet to cultivate? A shallow pass would give it a headache and encourage others to germinate in spring when it warms up before you drill it?

Cutting bg heads off stops them dead similar to glyphosate bur any not cut would not die
I have found that bg that is flowering is easier to kill with glyphosate than when it is at stem extension
My theory is that at stem extension the bg does not translocate glyphosate to the non emerged tillers and they send out a root and get past glyphosate whatever rate
Seedling bg needs very little glyphosate to kill it but very hard water needs a much higher dose
Glyphosate mixed with liquid Fert or other chemical (pre ems ) is also very effective
We should all save water off the roof for glyphosate use

 

[Kingcj]

Fair enough, your options are limited then. I should keep my eye on those fields in spring and give it another dose if necessary. Probably not considered best practice but .....

 

[Kingcj]

Cutting bg heads off stops them dead similar to glyphosate

I've found in spring when mowing field margins that black grass that has its head cut off grows another head very quickly but a smaller one, the more times you mow it the smaller the replacement heads become

 

[yellow belly]

I've found in spring when mowing field margins that black grass that has its head cut off grows another head very quickly but a smaller one, the more times you mow it the smaller the replacement heads become

I agree that cutting can miss some heads so glyphosate is the best option