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Attack of the Japanese beetles: Eradicating them the safe and easy way

Friday - 7/11/2014, 9:28am  ET

japanesebeetle.jpg
There are a lot of ways to deal with Japanese beetles, Toxic chemicals are never necessary. (AP Photo/North Dakota Department of Agriculture)

WASHINGTON -- Josefine over in Boyds has met the Beatles. Well, the Japanese beetles, that is. She writes: "They are turning my Japanese maple into a lacy-leafed mess! Using something like Spectracide to kill them is not an option, as lots of hummingbirds use this tree to access their nectar feeders. What can I do?"

Well, the first thing to do when Japanese beetles or other members of the scarab beetle family attack is to take down any Japanese beetle traps in the area. The lures on these traps are so effective at attracting the brightly-colored beetles that they can easily quadruple the number of evil insects swarming into your backyard.

If you want to use the traps correctly, place them at the far outskirts of your property, where they can intercept the beetles far away from your desired plantings. Or, even better, give traps to all your neighbors.

Step two: In the world of safe and sane pest control, spraying poisons such as Spectracide is never an option. Instead, blast the beetles or other insects off the plants they're attacking with sharp streams of plain water. Set your hose nozzle to fire its absolute sharpest stream, and knock the beetles right out of the tree or off of whatever plant they're attacking. Do this first thing in the morning, not the evening.

Studies have consistently shown that these non-toxic H2O knockdowns are just as effective as insecticides -- and much more emotionally satisfying.

The best modern sprays for beetle battles

Josefine wants to beat the beetles eating her Japanese maple without using anything that will harm her abundant nearby hummingbird population.

Well, Jo, two organic insecticides (substances approved for use in certified organic agriculture) are very effective: Neem, which comes from the seed of a tropical tree, and spinosads, a group of naturally occurring soil organisms. Both act as feeding deterrents -- insects that eat a little bit of the sprayed leaves should lose their appetite. If they continue to eat anyway, they die.

Just be sure to only spray the leaves of the tree and be careful not to get any spray on nearby flowers. Spinosads are harmless to humans and other non-insects, but can be toxic to bees for the first few hours after application.

And cover those hummingbird feeders or move them temporarily to another area when you spray, just to be on the safe side.

Maybe your beetles just need a good wash and wax

Two other completely non-toxic products are highly effective against Japanese beetles and other blatantly visible pests. Now, once again, I would always start with a knock-down spray of sharp streams of plain water early one morning.

The next morning, I would spray any remaining beetles (that I couldn't reach to satisfyingly squish) with either insecticidal soap or horticultural oil designed for use in the summertime. But not dormant oil, which is only for use in the winter. Professionally made insecticidal soaps and oils smother any pests they hit, and are extremely safe for people, pets, and plants.

Just don't hit any bees or other good bugs directly with the spray. There's no residual action with soaps and oils, You only kill the pests you soak with the spray.

Oh, and don't worry about the long-term health of the attacked tree. Its leaves have had enough time to photosynthesize the energy they need to regrow next season, when it's hoped the beetles won't be so bad. And some feeding by insects is actually good for most plants, as it naturally stimulates new growth.

Cut your lawn correctly to cut future beetle attacks

Josefine also wisely wants to know what she can do to limit future problems.

"When is the most effective time to apply grub control products? Fall or early spring? she asks

Well first, let's follow the life cycle of your foe, Jo. The beetles now feasting on area plants will soon begin mating, and the females will then be on the lookout for lawns that are scalped and sopping wet.

Females Japanese beetles lay their eggs in turf grass, and you can do two things to deter them from using your lawn as their nursery. One is to let the lawn dry out in between waterings -- the beetles won't lay eggs in soil that's dry at the surface.

Lawns with automatic sprinkler systems that water daily are at the biggest risk of beetle grub damage. Their soil is always attractively moist at the surface.

The other is to never cut lower than 3 inches. Female beetles won't try and fight their way through a thick and healthy turf. And, of course, a 3-inch cut and infrequent watering are also the biggest keys to having a great-looking lawn in general.

Best non-toxic grub controls for spring and fall

But Josefine is still waiting to learn whether to apply grub control products in fall or early spring.

Well, Jo, if you mean a water-polluting, highly-toxic chemical grub control, the answer is never. They're terrible for you and the environment, and they prevent natural grub controls from working.

Now, the nasty crescent-shaped grub form of Japanese and other scarab beetles is at its largest and hungriest in the late summer. That's when feeding by Japanese beetle grubs can really destroy the roots of a lawn.

It's also the perfect time to apply milk spore disease. A naturally occurring soil organism that's deadly only to beetle grubs, milky spore is only effective when grubs are actively feeding in warm soil, which occurs throughout August and September. Although stores display and sell it in the spring, milky spore disease doesn't work when applied in the spring, as the soil is too cold and the grubs aren't feeding.

Get the timing right, shun chemical grub killers and with one application of milky spore your lawn could be grub-free for years to come.

In the spring, beneficial nematodes are the treatment of choice. These microscopic predators seek out and tunnel into grubs before they can become rose-wrecking armored adults -- but they don't bother earthworms or other good soil-dwellers.

Typically acquired via mail-order (because they have a short shelf life, be sure to check expiration dates if you find them at retail), beneficial nematodes come in packages of several million that are the size of a small sponge. You open their sealed container, drop the sponge that's keeping them alive into a watering can and water them into your pre-watered turf in the evening -- after the spring soils have warmed up but before any adult beetles are active -- just in time to plant tomatoes and peppers outdoors.

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