Going Ninja on Japanese Beetles

The Mountain Xpress, August 2,2006

Japanese BeetleFirst one or two metallic green and copper beetles here and there, then suddenly, hundreds of munch-tanks on your prize rose bush or peach tree, devouring petals and turning green leaves to brown skeletons. Before you reach for the Sevin dust, consider these safer options.

Japanese beetles can start showing up as early as late May and last until September, but their peak activity only lasts four to six weeks. When I first discovered JB's on my grape arbor last month, it looked like there must have been at least 300 of them. Within a couple of days, however, I had gotten the population down to about 25, plus a few more scattered about the yard. If you have a concentrated infestation of a single tree, trellis, etc. and a few minutes to spare each morning and evening, then my advice should work well. You can't get them all, but at least there's only one generation to worry about: the eggs they lay in the ground in late summer won't emerge as adults until next year. Grubs could be devouring your lawn in the interim, but that's a separate concern.

The prevailing wisdom says that the best way to deal with japanese beetles in the short term is to gather them up by hand, and I have to concur. Granted, for those of us over the age of eight, handling insects can be a bit unnerving (to find out, put a few beetles in your hand and let them try to push their way down between your fingers). The good news is that one, they don't bite; and two, you rarely have to actually touch them. You can even use a hand-held vacuum cleaner, but that sort of spoils the fun. Think of stalking these space invaders as a fun game, like you're some kind of neo-ninja, and it won't seem tedious. If the thrill of the hunt pales after a few days, do as garden guru Walter Reeves suggests and find a child to do it: "at a nickel per bug, a trip to the ice cream store can soon be financed!"

Figure 2-1: Diagram of the Life Cycle of the Japanese BeetleThe problem with the beetle traps you can buy in the store is that they can trap thousands of beetles a day; however, they always attract more beetles to your yard than they actually catch. The only effective way to use such a trap, then, is to place it a few hundred yards away (i.e., in someone else's yard). Obviously, using traps requires some neighborly cooperation.

It is possible to make your own trap, perhaps a weaker one with a shorter range.1  There are also a number of "trap crops," i.e., plants (including weeds) that JB's love. You just pick the beetles off the trap plant. The problem once again is that you may attract more beetles than you catch. It's best, then, whenever possible, to avoid or remove plants the beetles like. These include smartweed, virginia creeper, wild rose and wild grape. You can find a list of others online (or just find out the hard way).

There are a number of plants which attract yet poison japanese beetles (like sugar and humans). These include four o'clocks, larkspur, white geranium, red or dwarf buckeye, and castor bean. Assuming these trap crops don't also attract more beetles than they kill, you might consider planting them for next year. Keep in mind, however, that these are poisonous to children and pets as well.

There are other methods: attracting birds, many of which love to eat JB's; introducing parasitic insects and diseases; and simply covering smaller plants with netting. These approaches were either too involved or just not feasible for my needs. I did try the biodynamic, that'll-teach-them method of putting my catch and some water in a blender and spraying that on the plants. I certainly found it repulsive, but even with habanero oil and tobacco added, it didn't seem to phase them. Fortunately, simply gathering them every morning has been enough– and not a bad way to get out of the house and keep tabs on my garden as well.

The cardinal principle of JB-hunting is that the early gardener gets the beetle. In the morning, japanese beetles are either too cold or too wet to fly. Evenings work too, but not as well. It's said that the beetles won't fly in the heat of the day either, but that's not my experience.

The easiest thing to do, then, especially if the beetles are too high up or too numerous (or onerous) to pick by hand, is get out early, spread a tarp out under the bush, vine, etc. and jostle the plant. When japanese beetles sense danger, they bail out. On the ground, they're usually very hard to see. Your mission, then, should you choose to accept it, is to intercept them in between. With a tarp under the plant, the job is easy. You just 'shake and rake,' gathering up the pickins like mulberries (only crunchier).

Japanese Beetles matingWith bushier plants, or as things warm up, the tarp method doesn't work as well. You may still be successful by holding a container under them or just your cupped palm. Beetles that have dug themselves into the center of rose or other blooms may need to be dug out.

Always look carefully before you reach for a bug. There are bound to be more, maybe even on the underside of the same leaf. If you haven't already noticed, these beetles are awfully "social." They can smell each other's parfum sexuelhundreds of yards away, and they don't hesitate to join the party. That's great for us: it makes them easier to find, and the more you get rid of, the fewer come. Your work has a cumulative effect.

If it's mid-day and there's no chance of getting a tarp under them that evening, you can at least shake the bush or tree and have them fly off, hopefully landing somewhere else. But keep in mind that this can spread them to other plants in your yard, where they will quickly make lace doilies out of your canna lilies, etc. if you're not patrolling the grounds daily. You'll notice that beetles start from the top of a plant and work their way down. They're also attracted to already-damaged plants, so removing damaged leaves can help.

So what do you do with them when you catch them? Some get satisfaction from squishing them. After your tenth or so squished beetle, however, practicality usually overtakes vindictiveness. Most prefer to drop them into a container with a little soapy water at the bottom (they're not good swimmers). If you have a lot of ground (or height) to cover, you can carry your sacrificial cenote hands-free by cutting two parallel two-inch slots in the side, running a belt through the slots, and wearing it on your hip.

For an interesting/gruesome variation, try placing your beetles in an open container without water. You'll find that the more you add, the more likely they are to stick around. It's as if they become unable to think for themselves and can't decide if they should stay or go. They clump together increasingly until they're one writhing mass, and it's not clear whether they're climbing all over each other to escape or to mate. I suspect that in excitation, whether sex or fear, they release the same pheromone. Either way, it looks exactly like a Hieronymus Bosch painting of hell. There must be something to learn from this.

In any event, not to prolong their suffering (or enjoyment or both), when I'm done gathering I put the frantic throng in the freezer and within a couple minutes they are immobile. I heard it's one of the more pleasant ways to die.

Whether you use the squish, soap, or sex method, you can put your expired bugs out for the birds, feed them to fish, or do some kind of art project with them.

So that's the "crouching tiger, hidden beetle" method of JB management. Remember to look at it as fun (at least on your end). Isn't that a good approach to life?

1 Directions for a simple trap can be found at http://www.ghorganics.com/JapaneseBeetle.html.