Pre emergent soil temp, or specific date?

Discussion in 'Pesticide & Herbicide Application' started by Shady Brook, Feb 25, 2003.

  1. Shady Brook

    Shady Brook LawnSite Bronze Member
    from Indiana
    Messages: 1,517

    Do you guys put down pre emergent according to a date on the calander, or do you check soil temps?

    I have been hearing from the extention office, and from some local guys the earlier the better to put down your pre M. Seems to me, you would get a longer more effective coverage time, if you waited til the Soil temp approached that neccesary for crab germination? Or are their other factors I am not considering. I would enjoy hearing your thoughts.

  2. kickin sum grass

    kickin sum grass LawnSite Senior Member
    Messages: 628

    it depends on how many customers you have. If you are large you have to start earlier to get it all done. I think you were from indiana..... You will want to have it down by the time the forsythias bloom. crabgrass germinates at the same time. That means all the environmental conditions are right for germination and blooming. Also you may want to try dimension instead of pre-m. it has longer residual so you can start earlier as well as some post activity. I have had better luck with it and only need 1 app for good results. this will free up your next app to apply another comb fertilizer if you need to.
  3. Shady Brook

    Shady Brook LawnSite Bronze Member
    from Indiana
    Messages: 1,517

    Thanks Kick

    Now I need to find a forsythias. :)

    So there is no need to be really early. Would it make sense to apply as late as possible to have a more lasting effect? I will not have a ton of customers, so that waiting will not be a problem if it works well.

    I think you are right about Dimension, seems really good. The one source I will use most does not carry much with dimension, he carries Team mostly. I can probably work something out to get the dimension from another source.

    Thanks again
  4. 1grnlwn

    1grnlwn LawnSite Bronze Member
    Messages: 1,261

    I wait as long as possible. Crabgrass starts to germinate at 55 deg so ground at about 50 deg works for me. May start earlier this year so weed and feed not so late.

  5. GroundKprs

    GroundKprs LawnSite Bronze Member
    Messages: 1,969

    Many labels on consumer pre-ems state to apply when forsythia blooms, and there is much literature that states the same. Getting your pre-em down before target weeds germinate is the key, and any manufacturer will put CYA speak on his label. I my area, crabgrass germinates 3-6 weeks after forsythia blooms. This is from observation, not from labels. A better indicator of crabgrass germination is the flowering of lilacs: crabgrass will begin to germinate after lilac blooms begin to fade.

    Of course, all of nature is not on the same clock. The north side of a large building can be 3 weeks behind the south side of the same building in April, because the south side has warmed up so much more. But there are generalities one can see over time. For one, if you service both city and suburban lots, you will note that the city sites begin growth about a week sooner than the suburban ones. That's simply because any crowded human environment is usually warmer overall.

    And remember, it is the simplest things that will guide you in the care of plants. I'm sure we could find multiple extensive documents on determining the timing of crabgrass germination. If you want to get it exact every year, just watch the cracks in walks, drives, and parking lots. That is the warmest spot in the environment, and the first place hot weather weeds will germinate, LOL.

    So if I see crabgrass in the parking lot, I better be sure to have pre-em on there in the next 10 days. But if we are having a tremendous heat surge, I might only have 2-3 days. Of course you need to know what germinating crabgrass looks like also.
  6. kickin sum grass

    kickin sum grass LawnSite Senior Member
    Messages: 628

    unfortunaltly you wont be able to see germinating crabgrass unless you carry a mag-glass. Think about how small a crab seed is, germination is when the seed first splits and starts to absorb nutrients to grow into a plant. once you see the plant no matter how small it is a plant and pre-m will be wasted. Even if you could see a germinating crab grass seed and you aplied your pre-m right then it is still to late. by the time it got in the soil and set its barrier the germinating plant would already be past the point of it being effective.
    you are right that it is a couple weeks after forsythia blooms so that is why you need to have it down by the blooming so it can set its barrier and be there when needed.
  7. dougaustreim

    dougaustreim LawnSite Senior Member
    Messages: 488

    WE use Dimension then we don't have to worry about the dates being as exact. Dimension has long residual and has post activity even after you can see the small plants.

    Austreim Landscaping
  8. J&R

    J&R LawnSite Senior Member
    Messages: 835

    March 1-15 on summer PM & broadleaf and Oct 1-15 on winter PM
  9. GroundKprs

    GroundKprs LawnSite Bronze Member
    Messages: 1,969

    LOL, kickin, not too many of us have time to lay in grass with a magnifier, watching for crab to germinate. It's just that much activity of nature is based on cumulative temperatures. Growing degree days (GDD), if you are familiar, is the best means of predicting activity in nature, much better than a given date or temperatue reading. And an understanding of phenology (the scientific study of periodic biological phenomena, such as flowering, breeding, and migration, in relation to climatic conditions), will help you to manage plants on specific sites. Watching what other plants are doing will tell you when to anticipate good or bad activity in/on other plants nearby.

    Ergo, when I see crabgrass plants (maybe ½"-1" tall, 2 leaf stage) in Dr. D's asphalt parking lot, and temperatures are acting normally for our area in springtime, I know that crab will germinate in his lawn in 10-12 days. Why? Because the asphalt has absorbed a lot more heat than the soil of the lawn, and the soil in the asphalt cracks is that far ahead of the soil in the lawn in cumulative temps, or GDD, for the year.

    And if you know what newly germinated crab looks like, it's easy to manage this way at Dr. D's, LOL.

    And even though we manage each site to the individual characteristics and problems of that site, there are many things we can correlate over all sites managed, over years of (open-minded) observations. I know that if dollar spot is going to flare up here, I will see it on Dr. C's lawn first, a day or 2 before any other. His location is the key. So when conditions are building for dollar spot, and we may have to treat it, I start my day with a drive past Dr. C's, usually no more than 2 min out of my way, if at all.

    And you can't get much of this post on labels, LOL. Remember there is a lot you can do outside the label. I rarely apply any pre-ems before lilacs bloom. But then I am cutting out pre-ems in near future, so you have to be careful about what I say, LOL.
  10. kickin sum grass

    kickin sum grass LawnSite Senior Member
    Messages: 628

    I see what you were getting at on the previous post. Hope I didn't step on any toes....
    I will agree 100% on your last post. By watching a lawn you know something happens to first, you know you have to start looking at the other ones and can know which ones can be treated later or sooner.
    Mother nature can tell you a lot about what is going to happen in the near future if you know how to read her.....

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