I've been hearing that a lot of people are recommending wasp spray as a bear repellant. Proponents argue it has a longer range, and is more accurate to aim.
How effective is wasp spray as a bear repellant?
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The suggestion to use wasp spray for defense seems to be common enough that there’s a Snopes page on the topic. This particular urban legend is more often brought up in the context of defense against people, but it seems now to have been extended to bears. I would stick with the bear spray.
In the US, the phrase “It is a violation of Federal law to use this product in a manner inconsistent with its labeling” will be found on pesticide containers. This is a hint that this may be a bad idea. Wasp spray usually contains poisons rather than irritants, which creates additional legal problems if you use it on people or bears.
Regarding the claims around range, a can of UDAP bear spray has a range of 30-35’ (9-11 meters). Wasp sprays tend to be effective out to 15-22’ (6-7 meters). This oversight may be due to the origin of the myth in an anti-human context: keychain style pepper sprays have a shorter range, although even the anti-human sprays are available in longer-range versions.
Regarding precision, bear spray presents in a conical cloud. Beyond close range that cloud will be about 100” (2.5 meters) in diameter. In contrast, wasp spray presents as a narrow stream, the better to soak a small nest rather than contaminate a larger area. This is a negative for the wasp spray, for the same reason that firearms are considered less effective than bear spray: most people’s ability to effectively aim goes away when under extreme stress.
Edit to add: The neurotoxins in wasp spray (usually pyrethins) have a far greater impact on insects compared to mammals. This comes from differences in body size, absorption, capacity to metabolize, and sodium channel sensitivity. For example, in cases where people have been sprayed, no incapaciting effects were seen.
To summarize, the claims of the proponents appear to be incorrect regarding range, misapplied regarding accuracy, and baseless regarding actual efficacy. As there doesn't appear to be a mechanism by which wasp spray would deter a bear, actual testing is unlikely to be performed.