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Japanese Beetle Bug Traps: Is there a Catch?

While some nature lovers among us may declare that Japanese beetles are a part of nature and should be permitted to chomp away at the greenery, I don’t find myself among that set. For one thing, if we want to extend that line of thinking, then clearly humans are a part of nature too; should humans be allowed to do whatever they want on the grounds that they are “natural?” For another thing, Japanese beetles are an introduced species in the United States, not part of the original ecosystem: they’ve been in this country for less than a century and aren’t being very well restrained. They certainly haven’t been that well restrained in my yard, taking the leaves on a newly planted Mountain Ash tree to pieces:

A Mountain Ash tree, before and after the introduction of a Japanese beetle bug bag

Some say that these “bug bags” actually attract more Japanese beetles than they trap. My experience, with two traps each placed about 40 feet away from the victimized tree in question, is that the traps work. The picture you see on the left is typical of the condition of the Mountain Ash tree before I introduced a Japanese beetle bug trap scented with pheromones and colored an attractive yellow; the picture you see on the right is representative of the current condition of the Mountain Ash, two weeks after I put a pair of “bug bags” up. The difference in the leaf condition is striking, with new growth being given a chance to leaf out before being chewed down. Before I hung the traps up, I’d find 6-8 beetles on my young tree every morning. By the morning after the traps went up, the Japanese beetles stopped coming to the tree and started falling in the bag. I haven’t spotted a single beetle on that tree since.

The Japanese beetle traps I’ve deployed don’t use pesticides that could harm other living things; they attract with a pheromone scent and physically trap Japanese beetles in a slick bag out of which they can’t climb. They seem to me like the perfect pest management tool in terms of effectiveness and environmental responsibility. Yes, they seem that way, which is why the cynic in me wonders whether there is some dastardly downside to these devices that I haven’t considered. Is there a reason I shouldn’t be hanging these bags in my yard?

7 thoughts on “Japanese Beetle Bug Traps: Is there a Catch?”

  1. Mark says:

    The Japanese beetle is an introduced species to the US and a serious pest. Killing as many as you can will protect native species of plants. By all means, trap away and be happy about it!

  2. J. Clifford says:

    If only there was a pheromone decoy for white tailed deer – not to trap and kill them, but to get them to go somewhere else! The deer in my garden eat entire tender branches, buds and all, not just mature leaves, and are a much worse problem than japanese beetles. Those people who say that the reintroduction of wolves would be bad for agriculture are only thinking about the livestock side of the equation. Vegetable crops are ravaged because deer don’t have adequate predation pressure from wolves any more.

    1. Jacob says:

      Everyonce in a while around here they allow for larger deer hunting permit limits in order to deal with that situation. Deers can become extreme pests and can be very dangerous when there are too many in popultated areas.

  3. Hendrix says:

    I would check what other kinds of bugs end up in the trap. It sounds like a fairly specific trap considering the quick success, and it seems unlikely you’re impacting other insect populations, but for the sake of science you might check if beneficial insects are getting trapped.

    1. Jim says:

      Good point, Hendrix: we wouldn’t want to trap helpful mantises or ladybird beetles, for instance.

      I have been checking, and I’ve seen nothing but Japanese beetles in the trap.

  4. Tom says:

    i tried them but found that they draw more beetles to the area, many of which go for the trap but others feed on plants i’m trying to protect. This year i physically picked them off and threw them into a coffee can with about an inch of equal parts water and bleach. i had about the same results, but far fewer beetles to deal with compared with the traps.

  5. Jim says:

    I’m wondering whether there’s some time correlation. Maybe if you put up a Japanese beetle bag early in the beetle season, you might find there are more beetles later because the peak comes. Maybe if you put up a Japanese beetle bag in the middle of the beetle season, you’ll be amazed at how beetle numbers recede because the peak has passed.

    I guess I’ll have to wait until next year for the full season’s effects to see if correlation implies causation.

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