Spruce Moths

Spruce Moths

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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Photo: Greg Thomas

Spruce Moth Prime Time

Spruce moth hatches have limitations. First, the hatch arrives when daytime temperatures can soar to 90-degrees F. or higher. The hatch typically starts during the first week in August, builds through the middle weeks, and dies before the end of the month. (Depending on air temperature and elevation, it may begin in early July and extend into late September.) Hatches get going around 8 A.M. or 9 A.M., just as the sun tops the mountains and warms the air. It lasts until noon or 1 P.M., when the heat really builds and the frenzy often dies. During a hot summer, emergency angling restrictions (especially in afternoon hours) may be placed on some of the streams where spruce moths are found.

A typical spruce moth day starts in the morning as air temperatures rise and the moths gain energy. As soon as they warm, they move out of the trees and begin searching for mates: first a few, quickly dozens, followed by hundreds or thousands depending on the location.

Spruce moths are strong fliers, but they are not immune to wind. In the Rockies, summer winds start early and deposit errant moths onto the water. The trout take notice, quickly moving from dark hiding places — around rocks, under logs, in the deeper pools and runs — into prime feeding lanes.

Trout often target moths in water shallower than 4 feet. If a Trico spinner fall is already in progress, the fish may switch from diminutive mayflies and focus instead on moths. A high-floating moth pattern with a Trico dropper tied off the hook bend is a good way to take advantage of both hatches. Look for fish along rocky banks where depth and cover offer security. You rarely focus on a particular rising trout — just cover the water.

Matching the Hatch

Fish are gluttonous and attack attractor drys like #12-14 Goddard and Elk-hair Caddis during early stages of the hatch. Occasionally, in their haste to devour a moth — or in an attempt to drown it — trout may miss your offering the first time, possibly even the second time, and return a third time to waylay their victim. If a fish misses, don't worry that you may have jerked the fly away and created a commotion — it's the same way naturals act as they try to escape the death tug of the surface film.

As the hatch progresses toward noon, gorged trout may get picky. For these fish, tie on a specific spruce moth imitation such as Gary LaFontaine's Spruce Moth — a pattern that has proven its merit on Montana's Rock Creek — or Patrick Daigle's Spent Spruce Moth (available from Blue Ribbon Flies, blueribbonflies.com). Brief delays in action often end with a strong gust of wind blowing more moths out of the trees, which can prompt another frantic round of feeding.

When the hatch subsides and the fish return to their picky, late-summer routines, downsizing your flies and tippets may solicit a few more takes. Early in the hatch, 4X tippet is fine (you might even get away with 3X), but later in the hatch, 5X may be required. Another late-stage tactic is to bypass picky fish. Sometimes the best thing to do is say, "You win," and move on to more willing customers.

Don't Miss the Show

Anyone who experiences a solid spruce moth event is fortunate, and those who fail to take advantage of the current upswing, especially in Montana and Idaho, are missing out. In fact, owner Doug Persico of Fishermans Mercantile in Rock Creek, Montana, thinks the sin is worse for dry-fly anglers.

"I think that a guy who passes up a chance to fish the spruce moth [hatch] is passing on one of the great experiences in angling," he says. "If you are a dry-fly fisherman, it doesn't get any better. It beats the Salmonfly hatch, and it even beats my dearly beloved spring March Brown hatch. The weather is great, the fish are eager, and they love spruce moths. Even the big fish come up for them, so you get the best of it all."

Ennion Williams, manager of Lone Mountain Ranch in Big Sky, Montana, has guided anglers during the spruce moth hatch for several years.

"It always came off around the beginning of August, but now it's beginning in July and lasting longer," he notes. "The patterns we use are the Stimulator or a light-bodied Elk-hair, size 10 or 12. The fish do get picky later in the hatch. You can change flies or tweak them to create a crippled version, or you can sink them.

Williams says there's no aquatic stage to the spruce moth, but the fish do eat drowned moths below the surface. The Gallatin has had a massive hatch the last few years and it brings up some of the largest fish. "It just takes over during a time of the year that used to be pretty slow."

That's also the way it is on the Big Hole. Last year, I couldn't help but consider my good fortune when the moths started out of the trees. The skies were blue and the morning was crisp enough to offer a shot of energy, but not cold enough to say that summer was ending.

There were only a few anglers spread over miles of prime stream. A half hour later I had landed a half dozen or more fish, including an 18-inch brown that broke my 4-weight rod. I raced to the truck, swapped the rod, and was back on the water ten minutes later to find the river alive with trout. Every cast drew a rise.

In the end, the value of the spruce moth hatch — or any super-productive hatch for that matter — is a chance to see Western trout at their best and to be able to tempt large fish to the dry fly. That's the spruce moth hatch, a late-summer bonus for anglers lucky enough to find it. It's not known how long the current spruce moth infestation will last. So get out there and take advantage while the taking is good.

Greg Thomas is a Fly Fisherman field editor, the author of five books, and publisher of Tight Lines. He lives in Ennis, Montana.

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