You aerated. You seeded. You watered. You fertilized.

You sat back and waited for your lawn to grow lush and thick and green just in time for summer, and now this.

A brown spot.

Then two.

Before you knew it, you had a full-blown crisis on your hands, a yard full of unsightly straw-colored blotches.

Take heart: You're not alone.

Turf-killing diseases, especially one fungus commonly known as leaf blight, got an early start thanks to a wet spring and are quickly spreading across Lancaster County lawns because of summer's heat and humidity, according to turfgrass experts.

"This is one of the worst cases I've seen in lawns in almost 25 years of managing turf," said Jeff Hazlett, the owner of Ever Green Tree & Lawn Care in Lancaster. "It's kind of unprecedented. I've never seen this much damage to turf."

The primary disease, ascochyta, has shown up in yards over the past three weeks, creating large irregular patches of yellowed grass.

Often, leaves infected with the fungus show bleached tips a third to halfway down the blade, according to Colorado State University's extension. The part of the leaf separating the healthy and diseased sections is abrupt and slightly pinched.

"It kills it from the tip of the leaf blade down, and, basically, it's the top of the plant that gets killed," Hazlett said.

Ascochyta is among five common yard diseases that are thriving this year, said Jim Welshans, a turfgrass specialist and educator with the Penn State Agricultural cooperative extension.

"With this humidity, I've seen a lot of diseases out there," he said. "It's been a challenging year for growing turfgrass."

The conditions are just right for all types of scary-sounding, turf-killing disease — ascochyta, red thread, brown patch, dollar spot, summer patch.

Eric Morgan of Lancaster-based Organic Approach said the fundamental problem is rooted much deeper, both physically and literally.

Many homeowners put down synthetic fertilizers that include salt and other chemicals that kill biological diversity and ultimately do more harm than good.

"The end result is that they are reducing, slowly but surely over time, the biological diversity whose sole purpose in life is to aerate soil and antagonistically compete with disease-causing pathogens," Morgan said.

He said many of the most pockmarked lawns can be found in new developments.

"In the last 10 to 15 years, builders have buried more stone," Morgan said. "You get rock outcroppings below the surface, and there's no fix for that."

Pockets of stone underground can lead grass to dry out more quickly.

So if you've got brown spots in your yard, what should you do?

For now — nothing. Turning on the sprinkler won't work.

"Just let it go," Welshans said. "I like to have a nice lawn, too, but I'm not one who likes to go in and waste water on grass. It's not going to do anything. And for home lawns, I'm never a pusher of using too many fungicides."

Hazlett estimates that 75 percent to 80 percent of lawns infected by the disease will recover on their own.

If it doesn't, here's what you do: Wait until September, mow the brown patches really short, run an aerator over them, rip up the blotchy grass and plant new seed.

But make sure you follow those instructions.

"Grass seed is like any other seed," Welshans said. "It needs soil contact to germinate. Too many times people just go out and throw it on top of the grass and then it doesn't germinate."

tmurse@lnpnews.com