Both insects and diseases are active in the Spring and Fall. I'm seeing mite activity, Dollar Spot Disease and weeds such as Dandelion, thistle and a few others. Crabgrass typically doesn't emerge until late May or early June. Dollar Spot can be caused by poor cultural practices such as waiting too late to start watering in the Spring and the lawn goes from extremely dry to extremely wet as the homeowner tries to "catch up" with heavy watering and get it to green up because their neighbor's lawn is so nice and green already. Also the heat tends to cause atmospheric conditions favorable for this disease. If you are watering good like you should and mowing properly; weekly at 3" with a sharp blade you are doing everything right as far as cultural practices go and your lawn STILL gets this disease it's because the heat combined with the moisture in the lawn creates humidity on the surface and is a condition favorable for the fungus to grow that causes the disease. Then there's good old Necrotic Ring Spot that's active in Spring and Fall and that's when it spreads the most. For more information on lawn insects and diseases please go to http://www.wienslawncare.com/lawntips.html or http://www.wienslawncare.com/products.html as I have videos on all these lawn insects and diseases that you can watch.