Yesterday I sprayed a mixture of Gly, Arsenal, a surfactant and water (about 60 gallons) on Cogan grass for a client. It was bright and hot, about 90 degrees. I finished about 1 pm and last night about 9 pm it rained. Wouldn't that be plenty of time after spraying that the rain wouldn't hurt the spray?

I would think so. If I remember the label correctly, Arsenal is supposed to be rainfast within the hour. With high temps, if the humidity wasn't terribly high, the gly should be ok as well.

Generally, if the plant has a chance to absorb the herbicide (it is completely dry after spraying) before it rains you should be fine. Based on your description of conditions it should have been good within an hour.

I believe if it was just about any other plant you'd be fine. Definitely ideal conditions and enough time before rain, but Cogongrass is apparently a tough SOB.

Two years ago it showed up in a cornfield in the eastern part of VA. Since then we have received information to be on the lookout for it. From what I've read, the mixture you used is about the most effective control I've seen, but it's not uncommon for Cogongrass to regrow after one application. If you would, later on, post the outcome of your application. Hope it works, I've read where it's a very serious problem in the south, especially FL and AL.

Here's some info, but you might have already seen it.

http://www.cogongrass.org/control.cfm


http://www.threatsummary.forestthrea...fm?threatID=82

The state of Florida has finally started doing something about the stuff, co-pay of about $90 an acre the first year of the program. It is very hard to kill. When stressed it can separate some of the roots that will later regrow, spray can cause the stress. It can also grow from the small seeds it blossoms in the spring. Those light little buggars can blow for 15 or so miles and recolonize. It usually takes 3 years of repetative spraying to completely kill it. Many areas of southeast Asia have it so bad that entire villages have had to relocate. If you have a very big patch of it, don't set a match to it unless you are prepared. It will burn like you have sprayed it with a diesel gas mixture. Spray any spots of it you find before it gets started in your area.

my experience with Gly is you'll be OK as well.

I can't speak for Arenal, no experience with it.

FH