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Discussion in 'Pesticide & Herbicide Application' started by Bull, Mar 13, 2005.
How do you determine this in relation to applying Pre M's???
Why not begin with your local extension office? I'm not sure what you're asking, to be honest.
Most crabgrass and other grassy weeds germinate at a specific ground temp. I'd have to look it up to find out specifically what it is. generally the ground temp method is better and certianly more accurite than the air temp method (3 days over 70 = crabgrass germination) I have a soil temperature probe somewhere, haven't used it in years. I pretty much went with getting the pre-em down before a certian date and leaving it at that. The weather effects everything and it's different every season. this year we are out early and I as well as other LCO's have all our 1st apps down already because of the temps that were in the 60's and 70's the past couple weeks. We could have eaisly waited now though as it's supposed to be higs in the low 40's and lows in the mid 20's all this week again with a good chance of snow! All this will lower the soil temps again and start the warming process over.
I am using Barricade which needs to be applied earlier than some to get activated before germination occours. Using demension you could delay your apps till later if need be or better yet use either in a split app and increase your pre-em window even longer. I'm in the transition zone so a split app or a high dose single app is what's needed to make it thru the summer...
Air temps? Ground temps? What about microclimates? - I have seen natural cycles 5 weeks off of general area activity because of microclimatic conditions.
Phenology can tell you what conditions are specific to each property location. Plants can tell you more than instruments.
PreM's work best when you apply them before the seeds germinate!
Sorry, couldnt resit, feeling spunky today
You have to like Jims answer.
Do a little detective work. I live in a basically cool climate. The grass begins to grow sometime in April/May. When you gents/ladies that live in these frozen places are out in that transition time look at certain areas to get some clues as to what is happening. Do you notice that areas around curbs, sidewalks, manhole covers in the middle of lawns are starting to grow and may actually have crabgrass growing while the rest of the lawn is brown. It is simple, the ground around these things IS warm enough to grow crabgrass and it is doing so while the rest of the lawn is still dormant. The sun is heating these dense structures of concrete and iron and the heat is transferred out to the adjoining soil.
That is in simple terms as to what I see and know that I am going to have to do a little Drive 75 spraying to catch up. All lawns do not hit the magical number at once. Local extension offices can give you historical data but I would be looking at the "clues" a couple weeks before that magical date. Good Luck.
Our state university has a web site showing soil temps all over the state in realtime. It is a great tool, but because soil temps vary from one lawn to another, they are a good guideline but microclimates do exist.
That's why it is best to just go by calendar and pick a date that is generally ahead of the germination window. When in doubt, apply it earlier and be on the safe side.