A: It could be mold but is probably algae. It can easily be killed with the hydrogen peroxide spray. Dilute the 3% grocery store product with water in a 50-50 mix and spray the problem areas.
A: The only thing that will solve this for sure is to dig a trench from the water holding areas to a lower point on the site where the water can run out. You don't have to put a pipe in the trench. Just fill the trench all the way to the surface with some kind of crushed rock. That way it serves as an inlet all along the trench.
A: If you aren't already, begin the organic fruit and pecan tree program. Stimulating the life in the soil is the only workable solution to the problems being created by the rain and super-saturated soils.
A: Look for slugs, snails and pillbugs. They have been prolific with all the recent rain. Sluggo and Sluggo Plus might help solve the problem.
A: I'm sure it's a pathogen related to all the rain and cool temperatures. To prevent further damage and spread, apply whole ground cornmeal at 2 lbs. per 100 sq ft and spray the subject plants with Serenade, potassium bicarbonate at a rounded tablespoon per gallon of water or a 1% mixture of hydrogen peroxide.
As a final comment – please turn the sprinklers off. You're wasting water and money as well as pouring gasoline on the fire! The enormous rain is doing enough damage without your help. I realize that most of you organic gardeners leave your systems on manual and don't make this serious mistake, but help me spread the word to those unenlightened ones.
P.S. Please donate to The Organic Research Center. TORC's mission is to stop the broad scale use of toxic chemical pesticides and fertilizers and to develop natural organic programs that work better in every way.