PESTICIDES DON'T WORK:  We applied chemicals for both insects and fungus, but the St. Augustinegrass still doesn't come back.   What's wrong? Broward County

ANSWER: Without more information, my response is speculative.   Were chinch bugs or brown patch present?  One should apply pesticides only against pests if they are present.  Here are some possible signs you can look for.   Chinch bugs are a common destroyer of St. Augustinegrass lawns.  The adult southern chinch bug is slate-black, with silvery wings, and 1/8 to 1/6 of an inch long.   Chinch bug damage usually occurs as distinctive patches, which may be initially circular, but later irregularly shaped.  Orangish-yellow dying St. Augustinegrass occurs on the perimeter of brown dead grass, and weeds occur in the dead center.  You should be able to find chinch bugs in the dying perimeter, by parting the leaves and thatch with your hands.

Chemical treatment can be ineffective against the southern chinch bug because of improper application and, less commonly, because of insect resistance.  Assuming hypothetically that there were chinch bugs, and that they were effectively controlled, the dead areas can take months to become recolonized from the surviving outskirts.  If the dead areas are larger than 5 feet across, you should resod or plug.  If there is a thick layer of thatch, you should loosen up and cart off the excess thatch to the compost pile, even if you are plugging.

Brown patch, in my experience, is not common, while there are other common maladies you should evaluate, such as take-all root rot disease, improper irrigation, and chemical injury. Hold off on chemicals until you figure out the problem.