Lefty Kreh is one of the world's best fly casters in part because he can't abide the idea of casting a fly incorrectly. Or, really, doing anything incorrectly. "Anything that irritates me, I try to do something about," Kreh said Thursday by phone from his Maryland home. "Except women."

Now 90 years of age and still fishing, still talking about fishing, and, most important, still teaching fishing, Kreh (pronounced "cray") will appear Friday through Sunday at the Great Waters Fly Fishing Expo at the National Sports Center in Blaine.

His teachings are regarded by many anglers less as instruction than orations delivered by a guru, and his arrival here is anticipated with the same excitement commonly associated with hooking a very big fish.

As the New York Times once said, if there is a rock star of fishing, Kreh is it.

Growing up poor on the East Coast, Kreh's family was on "relief," as it was called back then, and kids in his predominantly black neighborhood quickly tagged young Bernard, a natural lefthander, with the nickname "Lefty."

Now, among anglers worldwide, that single-word moniker is not so much a name as it is a brand, in the manner of Madonna and Sting.

The author of 31 books on fishing, with a 32nd in the works, and a frequent guest on television fishing shows, including the Outdoor Channel's "Buccaneers and Bones," Kreh was a multimedia specialist decades before Al Gore invented the Internet.

As a young man, Kreh contributed outdoors stories to local papers in rural Maryland. Some of these tales spoke of angling adventures on the small lakes and (then) clean rivers of Maryland and West Virginia, while others were treatises on soil alkalinity and how it can affect leaf color — interested as Kreh was not only in fishing and hunting but in the broader natural world.

Much of that world is different now, he says, than it was a half-century go.

"World War II changed everything about our land and water," said Kreh, who fought in the Battle of the Bulge. "When the guys came home, using the GI Bill, they were able to get educations, and a lot of them never came back to the small towns where they grew up.

"Essentially this broke up the feudal system that had been in place in America. Once middle-class people could buy their own homes, not just rent as they did before, what followed was the breakup of the countryside, where game had been plentiful and lakes and rivers were clean."

Kreh was the Baltimore Sun outdoors columnist from 1973 to 1992.

It was a great job until he needed more time to pursue what would become one of his passions: saltwater fly fishing, about which he is not only a highly knowledgeable expert but an adept practitioner.

Well known for his pinpoint casts in pursuit of bonefish, tarpon and permit on the Caribbean flats, Kreh insists the skills required to hook and land these fish are no different from those needed to fool brown trout in the small streams of western Wisconsin or southeast Minnesota.

"All strokes are identical with a fly rod, golf club, baseball bat, tennis racquet, hammer, Frisbee, even throwing a spear," Kreh said. "The initial movement is slow, then smoothly accelerates and stops. There are no separate motions — it is a continuous smooth acceleration to a stop — an instinctive and natural movement."

At this weekend's expo, Kreh will demonstrate his skills not only as a caster but also as a teacher.

"I've found the best teachers never display knowledge, they share it," Kreh said, adding, "to teach good casting, you have to be able to make all of the bad casts as well as the good casts, so people can tell the difference."

That said, don't expect "Lefty" to throw a line this weekend with his left arm.

In a misguided exhibition of domesticity some years ago that he now deeply regrets, he nearly tore his left biceps muscle from his arm while flipping over a mattress.

He's been casting righthanded ever since.

Editor's note: Show hours today are 3 p.m. to 8 p.m. Hours Saturday are 10 a.m. to 6 p.m., and on Sunday 10 a.m. to 4 p.m. More at greatwatersflyfishingexpo.com.