Idaho rivers have a host of unwanted organisms - from New Zealand mud snails (Silver Creek), to whirling disease and rock snot (South Fork of the Boise River) - and the list of threats to trout streams seems to keep growing.

Anglers can unintentionally transmit those things when they move from one body of water to another so they should be cautious to prevent transmission of harmful organisms.

Felt-soled wading boots have been the standard for many years because they provide excellent traction on wet rocks. But felt soles harbor mud, grit and vegetation and are slow to dry, so they are potential carriers of unwanted organism.

Some wading boot manufacturers, such as Simms of Bozeman, Mont., have introduced newly designed rubber-soled wading boots as an alternative to felt.

Like many anglers, I was curious to see how they would match up against felt-soled boots, so I recently gave a pair a try.

For background, I fly fish year-round throughout Idaho and typically take a few trips out of state every year. I own three pairs of felt-soled wading boots, including one pair with steel studs embedded in the soles.

My wading boots sometimes go weeks without completely drying, and I am not always meticulous about cleaning them.

I was interested in rubber-soled boots because I get tired of having saturated wading boots and have concerns they could harbor nasty little critters.

I tried some rubber-soled wading boots made by Simms that feature their "Streamtread" soles.

My initial impression hit when I first put them on. They felt more like a stout hiking boot than a wading boot, like I could strap on crampons and climb a mountain. As I quickly learned, that support helped my traction, which I needed.

My unscientific gauge of traction is the Streamtread rubber soles, which were designed and manufactured by Vibram, provided about 80 percent of the traction of felt.

But with the rigid sidewalls on the boots and the excellent ankle support, I was closer to 90 percent of the overall traction I would have had with my felt-soled boots.

Rubber soles should improve as companies continue to experiment with different tread designs and compounds.

The traction I got from rubber soles was well behind felt with studded soles, which are the gold standard of traction for me.

You have the option of adding studs to the Streamtread soles, and with that combination, I think the traction would at least equal - if not exceed -that of felt-soled boots.

But in my experience, studs have liabilities. They're like ice skates when I climb into my fiberglass driftboat, and don't do the floor of my boat any favors, either.

Studs also can be annoying when I am hiking long distances between fishing spots.

While felt soles provide excellent traction, they aren't perfect, either. They tend to wear out quickly, especially if you do lots of hiking.

I am no engineer, but I bet rubber soles are more durable than felt soles, which typically wear out well before my boots, and I usually end up buying new ones instead of replacing the worn soles.

If you fish during winter and walk in snow, felt soles turn into Frankenstein boots as snow and ice build up on the soles.

Felt soles also retain a lot of water and tend to saturate everything they come in contact with. That might not seem like a big deal until you have to pack wet boots in your luggage for a flight.

Rubber-soled boots are easy to clean, retain much less water and dry quicker.

Will rubber soles eventually replace felt? I doubt it for the simple reason that lots of companies make wading boots and there will always be a demand for felt.

But I think rubber soles are a viable alternative. The narrow gap in traction is offset by the durability and convenience of rubber soles.

There's still some argument about how big of a role wading boots play in transmitting harmful organisms, but I am confident the risk is decreased if I wear rubber soles instead of felt.

Simms plans to phase out all of its felt-soled boots by next year, and Trout Unlimited has asked other manufacturers to quit using felt soles by 2011.

I'm not going to toss out my felt soles, but I will be more careful to clean and dry them after they're used, and I am unlikely to replace them when they wear out.

When I weigh the advantages and disadvantages, I think rubber soles are the way to go.