Grey Spot, WTF!?

Discussion in 'Pesticide & Herbicide Application' started by Florida Gardener, Nov 18, 2009.

  1. This has been out of control since September down here in S. Florida. My best account that had fresh sod laid in may and has been fertilized twice since then and has looked picture perfect and has also been sprayed by a spray company 2 weeks ago had a little patch with it while I was over the other day. I'm getting really tired of this disease!
     
  2. greendoctor

    greendoctor LawnSite Fanatic
    Posts: 8,941

    I once had a bad experience with gray leaf spot on st augustine. It was my fault on top of that. I was growing in a lawn from sprigs. It was being irrigated twice a day, in the shade. Weather conditions at that time were hot and humid. I also put down almost a lb of N from urea to try and hurry the grow in. Gray leaf spot. It did not go away until the lawn was sprayed with Insignia, followed by 3336, followed by Eagle EW. All at 14 day intervals. That lawn never had gray leaf spot again. Since that time, I fertilize that lawn with potassium nitrate and micronutrients. No more urea. I have no idea what your spray company is using, but if I had to guess it would be propiconazole, which is the cheapest fungicide and also the least effective against gray leaf spot. I also have to look hard at how common lawn fertilizers are all urea based.
     
  3. Green

    The area of emergence is in full sun, and has been getting watered 2x/week. The weather has been high of 80-84 the past 2 weeks with very low humidity.
    Not sure what my spray company is using, but another of my customer's that they take care of had a small emergence as well( one of the neighbors has it bad 2 doors down) and they came back to treat and it is completely gone.
     
  4. txgrassguy

    txgrassguy LawnSite Gold Member
    Posts: 3,083

    How did you identify the Grey Leaf spot?
    Through a soil sample or from the technicians diagnosis?
    I ask as Helminthorsporium Leaf Spot may also be a factor.
    Regardless both diseases are exasperated by excess N fertility levels and poor/compacted soil conditions.
    Green offers a pretty good chemical control however I'd suggest an aggressive hollow core aerification with core clean up prior to additional control measures to alleviate the most common stressor to the site.
    Micro-nutrients are the most commonly overlooked control to assure a healthy turf site - and when coupled with an aggressive aerification and raking program wherein extensive bagging of clippings occur essentially all the stressors common to St. Augustine can be eliminated.
    Doesn't do well for the spray company profits though.
     
  5. By what the company told me and the signs matched the UF literature......Chlorotic patches of St. Augustine throughout the yard. Is the other disease similar to grey spot??

    This new sod was put down in May. My Lesco guy told me to fertilize after the 1st 6 weeks and then again 6 weeks from that point with the 15-0-15 dialed back a few notches(#16 instead of #19). The lawn looked PERFECT. It still does, except what appears to be grey spot popped up about a week ago. The company sprayed on the 4th and they are going back this week to control the disease. I just hit it with the 15-0-15 this week at the #16 setting. This isn't too much N, is it??

    All I know is this has been popping up everywhere the past 2 months down here. We haven't had steady rain since August either. In fact, since September, it has been pretty dry.
     
  6. txgrassguy

    txgrassguy LawnSite Gold Member
    Posts: 3,083

    First of all have you calibrated your spreader - those number settings are meant to be a starting point. Walking speed, variances in spreaders and material will all cause a difference between the set points and what is actually happening.
    From what you are saying about the amount of fert, what is the formulation and source of the Nitrogen?
    Stressed turf, including newly laid sod, should be fertilized very judiciously. Also without seeing the coverage of the irrigation system the salts in synthetic urea can easily stress the turf even beyond what Obama is doing to our economy.
    A good tip is to use the activated bio-sludge fertilizers like Milorginite when applying fert to new turf. No salts, a great ash content once the material breaks down and it is almost impossible to over apply - plus this stuff is great for microbial populations.
     
  7. ted putnam

    ted putnam LawnSite Platinum Member
    Posts: 4,539

    Especially when environmental factors, whatever they might be are cause for increased possibility of disease, you have to get out of the mindset that you are there to apply fert because its been 6 weeks. You are there to do what's best for the lawn at that time. Applying standard fert to St Aug that has much leaf spot in it at all is like throwing gasoline on a fire if those environmental factors persist. Some you can control, some you can't. Make sure the fire is completely out so you aren't just fanning the flames.
     
  8. I'm not just fertilizing b/c it has been 6 weeks. The lawn has been perfect(and still is) minus the very small area of the fungus. My Lesco dealer told me that the sod needs to root in and establish itself those first three months and that the 15-0-15 would help it do so. He told me to not apply as I normally would and to dial the spreader setting back. His recommendations worked GREAT. It has been 3 months since I last fertilized and gave the lawn a round before winter to go until early spring. Even on this round I dialed the spreader to the setting it has been for the first two apps.
     
  9. ted putnam

    ted putnam LawnSite Platinum Member
    Posts: 4,539

    Sorry, I misread. If you are fertilizing and another company is spraying( which to me is recipe for disaster) your schedules need to jive or it can end up being a case of a dog chasing his tail. As far as rates. Like someone else said, calibration is the key. Numbers are merely a reference point. I'm not sure if Daconil is still available but it is a great fungicide for solving the leaf spot problem. Good Luck
     
  10. txgrassguy

    txgrassguy LawnSite Gold Member
    Posts: 3,083

    Not to beat a dead horse but those spreader settings are there to assist in calibrating to ensure accurate applications.
    In the future I'd suggest pulling a soil sample first to acquire the recommended inputs and apply accordingly.
    High levels of quickly available salt based N sources on stressed St. Augustine is a sure recipe for pathogen problems.
    Especially when one considers how slow St. Augustine is to recover from injury.
    Catch cans are available for the Lesco spreader to aid in calibration or you can use what my crews do - a 7 mil thick garbage bag. It sure isn't pretty but it works.
     

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