Question
I have spots of yellowing ST Aug throughout my lawn.  It gets enough water and fertilizer and I've recently spread lime.

Can you help?  

Answer
June through September are typically rainy months in Florida -- and I'll just take a wild guess here that you are growing this Lawn in the Orange Juice State since it happens to be the most popular Lawngrass there.  If not please correct me and we will move on from there.

Yellowing in St Augustine is often a Chinchbug problem -- literally, Chinchbugs are THE most important insect pest of St Augustinegrass, at least in Florida.  The straw-colored patches usually begin at your Lawn's edge, up and down the driveway, during the hottest, driest Summer months any time between May and September.  But you maintain this Lawn has been diligently irrigated, and you are just coming out of a Hurricane Trifecta, yes?  Scratch Chinchbugs -- or better yet, get a vacuum cleaner out there and vacuum some of those Yellow Patches.  See if you DO have a Chinchbug problem.  If yes, tell me.

A related problem can result from TOO MUCH WATER and is made worse by what many ordinary people would consider a 'good Lawn care regimen' which involves over-fertilizing your St Augustine with a lot of chemical Nitrogen.  This tires out your Lawn by boosting chlorophyll and pushing up weak new growth, followed by thatch build-up.  This thatch layer makes a great hiding place for Chinchbugs.  Not only do they get to live it up down there, they do it with impunity, because the ordinary people figure they can use insect spray to exterminate everything.  Instead, you eliminate entire communities of friendly Earwigs and Big-Eyed Bugs, which prey on Chinchbugs free of charge. Alas, the Chinchbugs are NOT eliminated; they find more than adequate protection under the layer of thatch.  But we don't know for certain.  Careful vacuuming will find them.  Again, tell me.

Next, we consider Gaeumannomyces graminis, the 'Take-all Root Rot' disease.  An ectotrophic Fungus.  Suspect Number One.  Reason:  It erupts frequently after a great deluge, when rain has fallen in buckets and poured day after day.

Symptoms are described by a University of Florida Extension agent:

www.jacksonville.com/tu-online/stories/052105/lif_18783904.shtml

Unfortunately, one of the WORST things you can do when this strikes is apply LIME to your Grass.  Too late.

Still, we don't know if this is the cause of your Yellowing Lawn.  Inspect the roots of your Grass; this is where this disease strikes, not the Leaves (which suffer due to inefficient root systems and according to research may also be damaged by a toxin that Fungus produces as it attacks the roots).  Are roots strong and healthy?  Or are they shriveling?  Or are they disappearing (as though eaten)?  Look.  Tell me.

Another possible suspect: Pyricularia grisea, another Fungus.  But affected patches are more Tan, Brown or Gray than Yellow or Straw.  Maybe.  Maybe not.

That's the short list.  Read it and weep.  Get it out of your system.  Then get back to me and tell me what you've found -- or if you are NOT in Florida.

THE LONG ISLAND GARDENER