Photo: Greg Thomas

The West holds few hatch secrets anymore, and the best of the big bug action—Salmonflies, Green Drakes, and Red Quills—has been flogged to death in the literature and on the streams. What we dream of is a trip back to the 1950s and 1960s, when there were fewer people on the water and the hatches were still open for interpretation and discovery, including the delightful and rewarding construction of new fly patterns to match them.

This dream became reality when I slipped into southwest Montana’s Big Hole River and found moths falling out of the trees, and gorgeous browns and rainbows smashing the hell out of them. It was mid-August, a time when hatches are slow and the trout have been fished hard for three or four months. I looked upstream and down, and took in a visual mile—there wasn’t another angler on the water. But in every direction, hundreds of fluttering bugs peppered the air. Those that fell to the water were immediately slammed.

Making a Comeback

Those surprising bugs turned out to be spruce moths. And trout rose to my offering every time I presented it within a few feet. Some fish left their feeding lanes and plowed 4 or 5 feet through shallow water to bang the fly, providing the ultimate in trout-fishing visuals.

In the late 1980s through the 1990s, spruce moths were almost nonexistent on the Big Hole and other Western trout streams throughout their range, which begins in British Columbia and Alberta and dips south through Washington, Oregon, Idaho, Montana, Wyoming, Utah, Colorado, New Mexico, and Arizona.

The extended hiatus—a good thing for spruce and fir forests adversely affected by the parasitic moths—was influenced by natural conditions, namely extended freezing temperatures during spring, strong numbers of natural predators, and control measures applied by the USDA Forest Service. During the early 2000s the spruce moth, also known as the Western spruce budworm (Choristoneura occidentalis), returned—to dismay or delight, depending on which side of the forestry/fly-fishing fence you fall.

Entomologists, including Ken Gibson at the Forest Service’s northern region headquarters in Missoula, Montana, aren’t sure what influences the cyclical nature of spruce moths. But there’s little doubt that weather has a major impact. Conditions, right now and for the foreseeable future, are close to ideal.

“Spruce budworms work on a one-year life cycle,” Gibson says. “The eggs are deposited in the tops of trees in August. By September, the immature larvae hatch. They don’t feed during winter, they just spend their time in a silken case. In the early spring, just as the buds are developing and expanding, the larvae leave their cases and bore into the buds or feed on foliage.”

Spruce moths typically feed until the early part of July before they pupate and become adults. This happens over a two-week period. During warm years it may happen earlier, and during cold years it happens later. Typically, they are ready to fly by early August. Once airborne, they mate and then deposit eggs.

Gibson expects to see spruce moth populations continue to boom for the next seven or eight years, and possibly much longer. “Right now populations have rebounded from the late frosts we saw in the 1990s and they are really high,” he says. “Our aerial surveys show a million acres of defoliation in western Montana alone.”

The Secret Stash

If there’s an overlooked major Western hatch, spruce moths are it. The hatch is short-lived and it’s been mostly forgotten for ten years or more. It arrives at a time (the dog days of summer) when guided angling pressure is light—and it’s safe to presume fingers of larger rivers carry the moths and are missed by anglers targeting the known sections and documented hatches.

Some of the best waters where anglers are rediscovering spruce moths include the Big Hole, Madison, Gallatin, Rock Creek, Yellowstone, St. Joe, Kelly Creek, Clearwater, Lochsa, Selway, Middle Fork Salmon, Yakima, and the West Fork Bitterroot. Spruce moths are on additional waters ranging from large streams to tiny, forested tributaries of major rivers, including some roadless regions that beg to be explored.

When inquiring about spruce moth activity in Colorado, I learned that the bug is present throughout most of the western half of the state. It also has a presence along the Front Range, and it was most active during 2006 in southern portions of the state: specifically La Plata, Las Animas, and Huerfano counties. The spruce moth is affecting timber in the Gunnison, Rio Grande, Routt, San Isabel, and San Juan national forests, but I couldn’t find an angler or outfitter who knew if the activity translated to fishing opportunity. That should spark interest because fly fishers could spend an entire summer prospecting for an untouched hatch. The same could occur in Utah, Wyoming, New Mexico, and Arizona.

Topping the Heap

The Western revival of spruce moths signifies one of the best angling opportunities of the year, if not the best. Compared to some of the Rockies’ other noted hatches, spruce moths are smaller than Salmonflies and they don’t elicit the same kind of fly-fishing buzz. They do, however, come off when angling pressure is modest and water conditions are at their predictable best.

Spruce moths may not be as glamorous as Green Drakes but they’re more abundant. The moths are bigger and more predictable than major early-season caddis hatches, and the trout are bigger and in better shape during late summer than in the spring. Compared to Western Trico hatches, also present in late August, spruce moths may be less impressive in numbers, but you won’t waste time trying to thread 6X tippets through the eyes of minuscule #22 hooks, and once you get a fly attached, matching spruce moths means you’ll actually see your fly on the water.

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