DEBUNKING COMMON FLEA CONTROL MYTHS

What cold spell? An overnight low of 50 degrees is not a cold spell.

A "cold spell" suitable for killing fleas is roughly defined by parasitologist Dr. Michael Dryden as 10 days at 37o, or 5 days at 33o.

According to meteorologists, that last happened on the Coast in the Mesozoic Era, when the dinosaurs died.

More importantly, most of the pets we see in veterinary hospitals on the Coast are indoor pets. Do you think it has ever reached 33 degrees for 5 days inside your home?

Actually, a more important factor in flea survival is humidity. Like warmth, it is a commodity we have plenty of in South Mississippi, even in the wintertime.

Humidity in an adult flea or flea larva's microenvironment must plunge to 50% or less to be fatal. The microenvironment is the area immediately around the flea stage in question. For example, flea larvae like to go where they are in a dark and moist location, such as deep in carpet fibers underneath your couch. The air has to get a lot drier than when static electricity is produced to kill a hidden flea larva, and it has to stay that way a good while.

The typical wintertime scenario here is a rainy spell, followed by a cold front, followed by a rainy spell. On the rainy days, moisture is supplied heavily, with humidities in the 85% to 100% range. But even during the pretty blue sky days the humidity may drop to 20% in the daytime, and rise again to 85% at sunset. Since that time interval is too short to dehydrate the flea larvae, fleas are protected year round.

Indoor humidities are unlikely to vary more than 15% from outdoor humidities at any given time. Keep in mind, though, that outdoor humidities change constantly through the course of a day.

In fact, it is during the hot, dry part of the summer that fleas here are most endangered. You remember the hot, dry part of summer. It's the one we didn't have this year, because it rained through the whole part.

Instead of mild winters posing our biggest threat of bad flea infestations, warm wet summers promise us a good crop of fleas going into their favorite season, Fall. It is during this mild, wet season that they can increase their numbers and prepare to pester us all winter through.

Another common misconception is that rats, rabbits and squirrels harbor fleas that infest our pets. Actually, these species of mammals carry their own species of fleas, and if they get on pets at all, it is only transiently and they are unable to reproduce. Raccoons and opossums, though, may share fleas with dogs and cats.

My many thanks to Dr. Michael Dryden of Kansas State University, Parasitologist; Mr. John Hayden, refrigeration expert; and Mike Reader, Meteorologist for their technical assistance on this column.