Letter: Sealing Tree Holes to Mosquitos Is No Great Fix

Dear editors: On Saturday, April 16, the Record Searchlight published an article about mosquito season and how homeowners can reduce the populations of mosquitoes in their neighborhoods. Particular attention was given to treehole mosquitoes, which are a nuisance indeed. I’d like A News Cafe readers to know that trying to control these pests by sealing up tree cavities would do more harm than good.

These tree cavities, which can hold water year-round, are oases in our hot arid summers. They provide predator-free watering places for songbirds, lizards and even bats. (Yes, you can put out a birdbath for songbirds, but these just make the local feral cats’ job much easier.) Ever wonder where tree frogs, so abundant in the spring, sit out the long summer days until rain returns? That’s where.

All these creatures, of course, eat mosquitoes.

Don’t forget the “small majority” — the invertebrate neighbors who make up most of our world. Tree cavity oases provide the water source for honeybees, countless native flies and wasps who pollinate plants, and the tree ant colonies that are at the heart of the blue oak woodland food chain. If treeholes are filled, these creatures will be forced to mob dripping water spigots, where they’ll come into conflict with humans.

And the part of the cavity which holds water is just a tiny part of the whole. Like a damp vestibule to a vast and airy mansion, it leads to countless cozy chambers where owls, bluebirds, bats, woodpeckers and sapsuckers (to name a few) raise their young. We hear a lot about pollution and wildlife die-offs, but these flashy perils are not the biggest threat to wildlife by a long shot. By far the biggest threat to most creatures is habitat loss. Habitat loss is what you cause when you fill tree cavities.

Finally, consider what is best for the tree. Most arborists discourage homeowners from filling tree cavities, because we now know that doing so greatly increases trees’ susceptibility to fungal infections and blights.

So don’t try to fill tree cavities. The costs outweigh the benefits.

Wolfgang Rougle owns Twining Tree Farm and lives in Cottonwood, California.

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