I run a landscape design, installation, and maintenance outfit out of Central Ohio and I could tell you what we use as a yearly program, if that would help anyone out. Timing is approximate on an average year (last year everything needed to be applied 3 weeks early... this year you can apply a week or 2 late and be right on time).
1) a pre-emergent herbicide, mainly to control Crabgrass (and other hard to control weeds post-emergence), before April 1
2) a broad-spectrum post-emergent herbicide that acts as a "weed and feed", put down about now (early May)
3) a grub-killing pesticide with fertilizer to get the grubs before they become a nuisance, around mid-June (usually most expensive treatment. If they have a problem with top-feeding insects like chinch bugs, we would treat for that instead or in addition to the grub control)
4 & 5) 2 separate applications of slow-release fertilizers (NPK ratio = 30 or more-0-5), one in late Sept/early Oct, one in November (no pesticide or herbicide with it, just want to store all the energy in the grass as we can so it can carry over to the spring. It will go bananas the following spring, crowd out potential weeds, and look 2 shades of emerald green better than your neighbor who's not doing it. Most important of the applications. If you only do one or 2 lawn applications the entire year, make sure you do one or both of these).
As an add-on program, we do spot spraying every 4 weeks or so (depending on the label) with a selective herbicide (like SureGuard or Escalade, NOT a non-selective herbicide like Round-Up/glyphosate that will kill everything and leave spots in your turf). It takes care of a good deal of the major problem weeds like Dandelions, Canadian Thistle, Spurge, Oxalis/Clover, Chickweed, Bittercress, Ground Ivy, etc. without affecting the turf. You get a lot better results using a spot-spray in conjunction with a normal lawn program. We've taken yards that hadn't been treated in 2-4 years and got them into really good (borderline great) condition in 1 year.
If you have a lawn care program and you're doing more than 5 applications, you can risk burning your lawn out... especially if its being applied in the hot months when the lawn is generally dormant (July/August). It can do more harm than good. As a general rule of thumb, stay away from companies with high-pressure tactics (Trugreen Chemlawn are the poster boys for this) and stay away from companies that don't have their name on the side of their truck (if they don't even bother with that, they probably don't carry a state pesticide licence either). Choose a company where you know EXACTLY what is being put on your lawn and track the results, both positive and negative. It might sound common sense, but if you don't trust the company you are using wholeheartedly with your lawn, don't use them.
that is sweet. Would be awesome if you had a lot of land where you could drive straight-aways
