Grass must grow to fill in where feet, insects, weeds and fungus affect it. It can't do this when it's dry. It can die from drought alone -- starved -- even if none of those other problems exists.
Above, right: This lawn has dead spots and many weed violets. However, the problem is not disease, grubs or weeds. It's compaction and drought. Water runs off the hard packed soil here. What does penetrate is claimed by a thirsty maple. Aeration and more water in shorter burst are the answer.
A core aerator punches into soil, pulls out plugs and deposits them on the surface.
(For more, see 'Add Air" in New Lawn From Seed.)
The plugs dry, crumble and fall back into the pits over time. Air, water,
soil animals and microorganisms move into the pits and improve the soil.
Right: What about spiked shoes?
(Photo ©2013 JK c/o GardenAtoZ.org)
Save your money. Spiked shoes don't aerate worth a darn. Those with solid spikes simply pack the soil even tighter around the holes they may make. Those with hollow spikes either don't penetrate or need unclogging at every step.
Here are the cores pulled from a gorgeous lawn at one of the world's most beautiful and wisely tended public gardens. Each core is two to three inches long. Notice that the greenskeeper aerated only the most heavily trafficked area, along the walk, and pulled enough cores to temporarily change the color of the lawn.
Adjust watering where a lawn is most dry: sandy areas, space occupied by large trees, slopes that face south or west, etc.
Above: Early one spring on this south facing slope, lawn died from grub damage. The lawn was too stressed to handle even minimal insect damage. Our solution: Aerate, reseed, and water better. (More about this grub situation.)
Only one in five troubled lawns has grub trouble. Even then, grubs are often confined to areas were drought, poor light, compaction or low fertility are preventing the grass from keeping up with normal grubbery.