Question
I keep my st. aug (raleigh) cut at the highest level my mower will cut.  I have been fighting gray leaf spot for several weeks.  Firstly, is there a problem with the height of my grass in dealing with diseases.  Secondly, is there a good way of getting rid of and preventing gray leaf spot.  Lastly and somewhat off topic, my newly sodded back yard is not near as thick as my from.  I understand that it is new and will take time.  My question is how much time before my back yard is thick like the front??

Thanks for your time

Answer
One of the requirements for a disease to show up is humidity or dampness over a time period. The height of cut can contribute to this by preventing good air circulation. Rain falls late in the afternoon; the grass stays wet after the sun has gone down; late at night dew forms; early in the morning the sprinklers come on (I am guessing here). The lawn can stay wet for days!
Consider lowering the height of cut, cutting back on irrigation and witholding fertilizer applications.
Chemical appears to be the most viable option now. In the long term you can get on to an organic program but the results will take time.
The sod in the backyard must root in, start to function and supply the top growth with the raw materials for leaves and runners to start growing out. This process cannot be speeded up but you can facilitate it by providing the right things and conditions when they will do the most good. Watering is most important in the first eight weeks to the extent that it would be a waste to apply chemical fertilizers.
Be patient and watch Mother Nature do what She does best.