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Growing Degree Days

Discussion in 'Pesticide & Herbicide Application' started by heritage, Feb 11, 2004.

  1. heritage

    heritage LawnSite Bronze Member
    Posts: 1,268

    How many of you professionals are using GDD for insect activity as well as for timing your crabgrass pre-emergence herbicide applications. I have been using this system for 3 years and it really helps with monitoring and spraying pests at the right time. Using 25% less insecticides now with better results.
  2. KenH

    KenH LawnSite Bronze Member
    from CT
    Posts: 1,622

    I have a number I can call which tells me GDD and current insect activity. For crab pre., I use my own method.....:p
  3. Russ

    Russ LawnSite Senior Member
    Posts: 539

  4. Rtom45

    Rtom45 LawnSite Senior Member
    Posts: 456

    Penn State also has that information. I'll have to check the link and post it later. Very useful information.
  5. TSM

    TSM LawnSite Senior Member
    from MA
    Posts: 711

    Knowing GDD is a must. We dont use it in our lawn program but definately in our tree/shrub program.

    Thing is, even if you dont use this method, you should understand it. It is another way we can distingish ourselves from the homeowner or fly-by-nighter.
  6. Pete,

    Never heard of using Gdd for crab and goose control.
    What are the GDD total?
    I have always check soil temp at 3 in depth under turfgrass cover of average density. When soil temp is 55 degrees for three consecutive days at SUNRISE, you better have pre emerge down very soon!!!!!!!
  7. GroundKprs

    GroundKprs LawnSite Bronze Member
    Posts: 1,969

    Tim, I do not use GDD directly for pre-em timing, but I do find that phenological indicators are fairly accurate, and some of those relationships can be based on the same cumulative temperature data that GDD's are.

    For instance, I heard years ago that the fading of lilac flowers closely preceded the first emergence of crabgrass. (Most labels suggest that pre-ems be applied by time of forsythia flowering, but that is 4-6 weeks before lilacs fade. But then, manufacturers always build in a big safety margin.) I have used this indicator in my area for 20 years, and have never been burned. You don't wait for the lilacs to flower, unless you want to reduce early stress on some weak turf areas. But when you see them start to flower, you know you only have 10-14 days to finish up your pre-ems.

    Of course, you need to qualify your indicator plants, and be aware of microclimate conditions. A lilac on the shady north side of a three story building would not be a good indicator for the sunny lawn on the south side of the same building.

    GDD's and phenology are much more developed for insect and disease problems in ornamentals - not really used that much for turf.
  8. heritage

    heritage LawnSite Bronze Member
    Posts: 1,268

    Crabgrass starts to germinate around 150 GDD Base 50
    25% Germination at 200 GDD
    75% Germination at 600 GDD
    100% Germination at 1100 GDD
    Based on a study done at the University Of Maryland.
    I do a split app and begin around 50 GDD and finish round 1 before 150 GDD
    Last year our 1st GDD accumalation was march 16th and we were at 50 GDD on march 28th. We were at 150 GDD on april 28th and 1100 GDD july 4th.
    Forsythia dropped blooms here avarage april 26th...this is when soil temps are around 55F at 2". Phenological indicators are a great way to monitor also.....I have just found GDD to be easier all around for me. I do go by averages and do understand that there are microclimates with variations like southern exposure w/ poor air movement ect.

    Thought this might be interesting to some professionals unaware of this method.....I like it a lot!

    Pete D.
  9. Rtom45

    Rtom45 LawnSite Senior Member
    Posts: 456

    For growing degree day information in PA. and surrounding states, go to http://www.psu.edu/ur/search.html Type in growing degree days. Google search will bring up about 10 pages of listings with relevant information. You should also be able to refine and narrow your search from there.
  10. grassguy_

    grassguy_ LawnSite Senior Member
    from Ohio
    Posts: 633

    I use the GDD for insect monitoring thru Ohio State's website. Thay have monitoring sites or numbers for various areas of Ohio. The person to catch if you want some more info on GDD models is Tremor here on the board. I know last year he was working or trying to put one together that was primarily insects in general.

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