It's difficult to diagnose a lawn problem and recommend a correct treatment with limited information. Photos of your lawn damage would be helpful (close-up, farther away and from a distance showing damage patterns). There could be a variety of reasons that involve a number of factors.

What makes you suspect it is insect related? If insects are killing your lawn, you would be able to see many insects causing the damage. Or, if you think its grubs, pulling up a 12-inch section of lawn you would see a large number of grubs.

http://extension.colostate.edu/topic-areas/insects/billbugs-and-white-grubs-5-516/

I would not recommend treating with Spectricide until it is certain what insect you are treating for, if indeed it is an insect.

Most lawn problems are irrigation related. If you have an automatic sprinkler system, have you recently done an irrigation audit to determine if the lawn is receiving proper water coverage? In lawns with slopes or hills, irrigation runoff can be a problem so running multiple, shorter cycles is recommended.

http://extension.colostate.edu/topic-areas/yard-garden/operating-and-maintaining-a-home-irrigation-s...

A large number of lawns this year are suffering from mite injury due to the warm, dry winter. There are [3] photos attached that show what mite damage looks like. And here is a CSU Fact Sheet on mites:

http://extension.colostate.edu/topic-areas/insects/clover-and-other-mites-of-turfgrass-5-505/

Another issue affecting lawns is Ascochyta leaf blight. This is a fungus in which leaf tip dieback extends halfway down the leaf blade. Here is more information:

http://csuhort.blogspot.com/2017/05/ascochyta-leaf-blight-on-lawns-2017.html

http://extension.colostate.edu/topic-areas/yard-garden/ascochyta-leaf-blight-of-turf-2-901/

Other information that is helpful in a diagnosis:

• What kind of lawn variety do you have? Kentucky bluegrass, turf-type tall fescue, fine fescue or a warm season variety?

• Has this problem occurred in past years or is this the first time?

• How big of an area is affected? Smaller, scattered areas, one localized area, the entire lawn, only south or west facing areas?

• Describe what the lawn or damage looks like? Is it completely dead, yellowing, dry looking, have rings or circles?

• When did you notice the problem? Last fall, early spring, last week?

• What are your normal lawn care practices? Aerating, mowing, mowing height, fertilization, pesticides?

• Do you have a sprinkler system? What type of heads, number of days and length of time?

The best thing to do would be to contact the local extension office. They will gather more detailed information from you and provide guidance based on your answers. Arapahoe County CSU Extension Office is<personal data hidden>. They can also provide you an email address in which to send photos, or if needed, ask you to provide a turf sample.

More lawn care facts sheets:

http://extension.colostate.edu/topic-areas/yard-garden/#yard

http://extension.colostate.edu/topic-areas/insects/?target=publications