Roundup and the colour of dead weeds!

I need to spray several acres two or three times a year. I've used several brands of Glyphosate (never Roundup as it's too expensive) but all brands at the standard (360 ?) strength. Over the past five years that I've been doing it, I've found that the visible effects can vary quite a lot, even within one brand. After several trials, I've settled on a dilution of 1:80, i.e 125ml in 10 litres of water. I have many varieties of weeds, some more pernicious than others. Sometimes there are visible signs (yellowing, wilting) within a couple of days. Sometimes this is longer. My theory is that the varying rates of decine depend largely on weather conditions. If the weather is generally cool and/or damp it can take more than a month for total collapse. If the weather is hot and dry then the weeds can be totally crisped within a couple of weeks. I suspect that the glyphosate (if properly applied) has much the same effect but that the speed of collapse may depend on extra stress factors (e.g. hot drought). However, the final outcome is always the same. Of course depending on the time of year, regrowth can occur relatively soon afterwards if flowering and seeding has happened before spraying.
For what it's worth.

Replies

Kirsty Blair May 12, 2010 at 10:53pm

After 7-10days the weeds should be well dead. Did it rain (or snow) within the 8hrs of spraying - some of the R/up may have washed off - just a thought.
Bigyin May 13, 2010 at 9:16am

I need to spray several acres two or three times a year. I've used several brands of Glyphosate (never Roundup as it's too expensive) but all brands at the standard (360 ?) strength. Over the past five years that I've been doing it, I've found that the visible effects can vary quite a lot, even within one brand. After several trials, I've settled on a dilution of 1:80, i.e 125ml in 10 litres of water. I have many varieties of weeds, some more pernicious than others. Sometimes there are visible signs (yellowing, wilting) within a couple of days. Sometimes this is longer. My theory is that the varying rates of decine depend largely on weather conditions. If the weather is generally cool and/or damp it can take more than a month for total collapse. If the weather is hot and dry then the weeds can be totally crisped within a couple of weeks. I suspect that the glyphosate (if properly applied) has much the same effect but that the speed of collapse may depend on extra stress factors (e.g. hot drought). However, the final outcome is always the same. Of course depending on the time of year, regrowth can occur relatively soon afterwards if flowering and seeding has happened before spraying.
For what it's worth.
Bigyin May 13, 2010 at 6:58pm

Or a drop of washing up liquid.