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Japanese Beetle Trap
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Tackle nasty lawn grubs NOW—Before they can grow up into Japanese beetles and other pests!
Q. Dear Mike - I am turning the front yard into a garden (perennials and shrubs) - no more lawn mowing! In the process of trying to break through the clay I found lots of grubs. This probably explains why I had so many Japanese beetles last summer! My organic options seems to be nematodes, which look like they need to be applied each year, and a 'milky spore' that is said to last ten years or more. What do you recommend?
---Ellen, Esq. In Wynnewood, PA
Hi, Mike. We moved into a new home, and have grubs by the ton! Literally every shovel full of dirt I turned over while putting in new flower beds last Fall unearthed at least a half dozen. I'll probably be most inclined to take action if you tell me that they'll also devour the roots of the flowers we're planting. Thank You, and keep up the great work!
---Vince in Coopersburg, PA
My lawn needs desperate help. My main problem is grubs - Japanese beetle and Masked chafer are both present, and I have brown patches in the lawn.
---Linda; New Stanton, Pennsylvania
A. "Desperate help"? Is that like "Desperate housewives"? Or just a reference to what kind of assistance you expect here? Let's see how desperate we can get…
White grubs—ugly grayish-white crescent shaped creatures—are the larval forms of a number of beetles. The best known is the Japanese beetle, but grubs can also be baby beetles of the May, June, Asiatic garden, or Oriental variety; or Northern, Southern or European masked chafers. (http://ohioline.osu.edu/hyg-fact/2000/2505.html)
If you're game, you can identify your exact grubs by their distinctive hinders. Yes, only You Bet Your Garden could bring you a University paper that will soon have you scrutinizing your nasty grubs' rear ends—you just don't get this kind of service from other gardening shows!
The adults all have the same basic body type—the classic 'scarab beetle'—and pretty much follow the same life cycle. Adults emerge in early summer, copulate as they defoliate (most of 'em, that is—some adult beetles don't bother plants at all!) and then the females lay eggs mid to late summer. Japanese beetle females only lay their eggs in sod—so if those are the only grubs you have, your flower roots will be safe. But others, like May and June beetles, lay their eggs in plain old dirt, and their grubs will eat the roots of flowers and veggies.
Anyway, the eggs hatch quickly, the grubs feed on roots (grass for most, but ornamental plants for some), go through three fast molts and are about an inch long and eating a ton by Fall. When the weather chills, they drop below the frost line, moving back up when the soil warms in Spring.
Large numbers of grubs feeding in a lawn will cause brown patches that look like drought stress to appear in late summer. To make sure that grubs are the cause, lift up these dead areas when the pests are close to the surface—in general, August and September in the Fall, and April and May in the Spring (as soon as soil temps reach 60 degrees). Got grubs? You have two good options to knock them out before beetles fly this season.
"The Spikes of Death" is the nickname a researcher gave those lawn-aerating sandals you see in garden catalogs (just search the term "lawn aerating sandals" on the web). Now, these things don't aerate lawns—you need to pull up plugs of earth to do that; but they are the perfect length to spear grubs when the pests are close to the surface. Just walk overtop of your brown patches this Spring when a soil thermometer says the dirt is 60 degrees and you'll kill more grubs than an insecticide. Same thing in the Fall. Be sure and think good thoughts as you dance.
Beneficial nematodes are microscopic wormy little guys that come packed five to 50 million in little sponges. You water them into a wet lawn on a warm evening and they work their way down below the soil line to prey on grubs. The members of a newer strain (Heterorhabditis species as opposed to the older Steinernema types; pay attention—there's going to be a test after the show) are more aggressive and mobile, actually going after the grubs as opposed to lurking in wait for them. When you buy nematodes make sure their scientific name starts with an 'H', and not an 'S'. (Gardens Alive "grub away" nematodes are the right species, and they offer two kinds—one for Southern lawns, and a 'Northern' variety that is active in cooler soils.)
Yes, you do need to reapply the nematodes every year (the same is true with toxic insecticides, which you won't even consider using because you're too smart to poison yourself, right?). You can release them in Spring or Fall. Or both if you need to control a really severe grub problem. They won't harm good soil dwellers, like earthworms, but are effective against some other lawn pests, AND they kill flea larvae in your lawn, which makes Springtime release a really, really good idea if fleas have troubled you in the past. They are very cool little guys.
Milky spore disease is one of the oldest organic remedies. (Here's a great scientific article about it: http://www.ag.uiuc.edu/cespubs/hyg/html/200120b.html; you can find it for sale at most large garden centers.) Apply it to a lawn as directed once every summer three years in a row and it will build up enough disease spores in your turf to prevent grubs for a decade or two. But it doesn't have much effect the first couple of years, and it only works on Japanese beetle grubs. So check them hinders.
One of the most effective controls is to simply avoid watering your lawn in the late summer egg-laying season; the eggs will die if the turf is dry. Don't chase starlings; these so-called 'pest' birds feed on the grub-babies in your lawn and adult beetles! Another great natural enemy is the Spring Tiphia wasp; the female goes down into the soil and lays her eggs right on the pests, killing up to 85 percent of the grubs in a lawn—better than nasty chemical insecticides! Plant for sythia, peonies, and fire thorn to attract these great beetle-killers; and don't kill what looks like winged carpenter ants visiting those plants in the Spring; those are the wasps!
And finally, don't plant the adult beetle's favorite foods near lawns if you can help it. With Japanese beetles, that means keeping the roses away, of course. With other types, it's fruit trees and shrubs. Check them grub hinders and then go look up what Mom and Dad like to eat.