top three garden enemies: poison ivy, cigarette butts, and japanese beetles.
today, we conquer how to conquer japanese beetles.
as for the other two–i can discuss poison ivy eradication in a future post. but, as for those nasty butts…somehow it’s socially UNacceptable to spray horticultural oil on smokers? go figure.
so, japanese beetles. they eat, they hump, they decimate. the first thing we should understand about them (especially if we’re using the IPM approach) is their life cycle: they start out as those nasty white grubs in the soil below the lawn that you see when you are eagerly plowing out new beds with your shiny new shovel in the spring. they overwinter in the ground, pushing up and snacking on plant roots as the weather warms. as you unearth them, throw them in the trash. the life you save may be your own rose’s. exposing the tasty grubs for your bird allies–chickens, starlings, and native birds–is another benefit to hooking or cultivating your soil, which should be a part of your maintenance routine.
if you have a nice piece of property and you’re interested in a long-term solution to your JB problem, then milky spore may be something to look in to. purchased in large cans, milky spore is a powder infused with the bacteria bacillus popilliae. applied in a grid-pattern across your lawn for two or three consecutive years, this biological control can be effective for up to fifteen years…of course, there’s a catch. japanese beetles can travel up to five miles, so your neighbor next door or your neighbor in the next neighborhood’s beetles can re-infest your sanctuary. though, after applying milky spore to a client’s landscaped property just this spring, i have seen a notable decrease in plant damage. the best idea–no matter what you choose–is to take some step(s) at level one, when these bad babies are still underfoot. in the moment of quiet balance between spring and summer is the time of decision. what plants, what colors, how tall, what shape…folded into these decisions should be pest-repellent and -resistant plants. to repel japanese beetles, chives, catmint, tansy, and rue are good choices mostly for their odorous qualities. resistant choices include lilacs, rhododendrons, yews, and others with a waxy leaf and sturdy flower. quite opposite of repelling and resisting are the trap-crops, that draw the pests to them and away from your favorites. the sacrificial plants–er, i mean the trap crops for japanese beetles include evening primrose, marigolds, larkspur, and white or pastel zinnias. go ahead, throw them to the wolves…
so they grow up, and they grow up, and they grow up…into shiny beetles with voracious appetites. and now we’re talking about a population level that is out of control, or at least out of your comfort level. those characteristic skeletonized leaves are everywhere and you’re pulling out your hair with frustration. time to revisit the four tiers of IPM…
identification & monitoring: achieved
action threshold level: achieved
control: poised for combat
as always, begin with the least of the list of evils, mechanical controls. this case, in the morning, spread an old sheet out beneath the infested plants and give a good shake. the dew on their wings paired with the cool morning air makes the beetles lethargic and easy targets. empty the sheet into a bucket of soapy water. this bucket can be taken around to ‘spot clean’ single plants if the sheet isn’t necessary.
as far as biological controls at this stage, pheromone traps (available at downtown home & garden) or homemade baited traps (water, sugar, banana, and yeast in a plastic bottle with the top off) can draw in scores of the beetles, and can be disposed of in a fairly non-gross manner. however, if you are into gruesome, try harvesting one cup of beetles, setting your blender to puree, and applying through a hose-end sprayer. a bonus to this is if you use beetles infected with the milky spore bacteria, you can reuse the bacillus-infused beetles to perpetuate the spread of the biological control. alternatively, a pesticide like rotenone-pyrethrin (made from tropical plants, effective on hard-bodied insects and made from chrysanthemums, effective on soft-bodied insects, respectively) will kill the beetles quickly and effectively. a word of caution–rotenone-pyrethrin isn’t picky about what it kills–beneficial insects and fish aren’t safe, so use only when necessary and only as much as necessary.