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Answers to your gardening questions |
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Complimentary Copy of "Keys to the Garden Gate" Five-part article series on flower-drying starts here Eight-part article series on vegetable gardening starts here Asian
Lily Beetles Japanese
Beetles An
effective Deer Fence! |
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Japanese
Beetles "Help! Japanese Beetles were especially bad this year. We put up three traps and had more beetles than anyone else in our neighborhood! What did we do wrong?"  About half of the gardeners we questioned
also felt there were increased populations of Japanese Beetles this season; the other half
said there were fewer. Oddly enough (on the surface, at least) most of the
"more beetles" half had installed commercial pheromone traps in their gardens or
on lawns. Japanese beetles literally flocked around traps. If anyone can be
faulted, it certainly isn't you. If the trap manufacturer had bothered to print a
simple warning on the label, you would have been in the "less beetles" half!
Seems to me it wouldn't have taken a rocket scientist to anticipate the hoards that would
be attracted to exactly the wrong spot! (There's a lot of that kind of
lack-of-information (or, in many cases, misinformation) going around. Puts me in
mind of the misinformation which peat moss producers print on their bags encouraging
consumers to use three or four inches of fresh peat moss as a mulch. Gives me the
"willies" just thinking about it!)
So, clearly, the manufacturer is more responsible for seasonal beetle woes than most hapless gardeners. You see, beetles are attracted to traps from quite a distance. Putting a trap in the midst of a garden is tantamount to sending out engraved invitations to the dinner table. True, many of them will get caught in the trap but not before they inflict serious damage to nearby (expensive or treasured) landscape plants. If that was your experience this year, you would have been far better off buying traps for your neighbor and having him place them in his yard! Next year, if you feel you must purchase traps, place them far upwind of your garden. A light breeze will carry the pheromone scent across the yard, beetles will "smell" it and fly out of your yard and in the direction of their demise. Deceptive . . . but effective. Here's some encouraging news:
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More About Japanese
Beetles - Welcome through Our Garden Gate! So . . . the gardening season is over. But not questions concerning some particularly annoying problems this year. A friend called Monday (November!), wanting to know if I had any idea why her tea-rose was just beginning a new flush of flower buds. And while Linda and I were driving near Augusta last week we were startled to come upon a crab apple tree with flowers on it. My grandmother would probably have responded to the sight back in the '40s with "It's all those atom bomb tests that're causing all these weird happenings!" Flying saucers were a frequent topic of discussion as well. If she were alive today she might say something like "Yep! El Nińo! It happens every 7 or 8 years!" As for me, I'll not venture a guess. What's certain, however, is that some mighty strange things have been goin' on around here! Some things simply resist explanation, while others are so easy I'm surprised everyone doesn't already have the answer. Listen to this frustrated gardener's recent plea for help: "Help! Japanese Beetles were especially bad this year. We put up three traps and had more beetles than anyone else in our neighborhood! What did we do wrong?" About half of the gardeners we questioned also felt there were increased populations of Japanese Beetles this season; the other half said there were fewer. Oddly enough (on the surface, at least) most of the "more-beetles" half had installed commercial pheromone traps in their gardens or on lawns. Japanese beetles literally flocked around traps. If anyone can be faulted, it certainly isn't you. If the trap manufacturer had bothered to print a simple warning on the label, you would have been in the "less beetles" half! Seems to me it wouldn't have taken a rocket scientist to anticipate the hoards that would be attracted to exactly the wrong spot, Duh! What a clever way to sell more traps! Buy a trap; attract more beetles. Buy a second one to handle the increased load; attract more beetles. Keep buying traps and filling up bags...and the beetles just keep showing up. Mightn't be a bad idea to invest in the trap-making company!
So, clearly, the manufacturers of pheromone beetle traps are more responsible for seasonal beetle woes than most hapless gardeners. You see, beetles are attracted to traps from hundreds of feet away. Putting a trap in the midst of a garden is tantamount to sending out engraved invitations to the dinner table. True, many of them will get caught in the trap but not before they inflict serious damage on nearby (expensive or treasured) landscape plants, mate, and lay their clutch of eggs in yours or your neighbor's lawn. If that was your experience this year, you would have been far better off buying traps for your neighbor and having him place them in his yard! Next year, if you feel you must purchase traps, place them far upwind of your garden (100- to 150-feet). A light breeze will carry the pheromone scent across the yard, beetles will "smell" it and fly out of your yard and in the direction of their demise. Deceptive . . . but effective. Pheromones, you see, effectively announce: "Here's where the action is." Get the point? Here's some encouraging news: Researchers at North Carolina State University have learned that Japanese beetles will avoid eating leaves of certain varieties of Prunus trees—cherries and related species—which contain high levels of the chemical, prunasin. When Japanese beetles eat plants with high prunasin concentration, these enzymes cause prunasin to convert to cyanide. While the levels of cyanide are not enough to actually kill beetles, it certainly acts as a deterrent, discouraging further feeding. This information could very well lead to the development of plants— other than cherries and prunes—having stronger resistance to this pest. Who knows, it might even lead to a natural pesticide or repellant derived from the leaves of cherry trees! I'll watch future research and keep you posted. In the meantime, don't forget to roll up that garden hose and drain all the gasoline out of your mower, tiller, shredder and trimmer before bringing them indoors for the winter. Now a surprise: There's now a new Japanese Beetle predator: Now a new “star” has emerged onto the gardening scene: Istocheta aldrichi — a small Tachinid fly whose chief aim in life is to locate small beetles upon which to glue their eggs. It was actually introduced in 1922 specifically to parasitize — and therefore control — destructive agriculturally-important insects. They look very much like common houseflies, the difference being that tachinids nearly always remain outdoors and feed chiefly on nectar, honeydew and, occasionally, pollen. They deposit only eggs, and have extra bristle-like hairs on their abdomen. Common houseflies, on the other hand, have much shorter abdominal “hairs,” seek out garbage, carrion, outhouses, and leftover food scraps upon which to deposit their live-born larvae (“maggots”). Here’s how tachinids get the Japanese Beetle destruction job done: * Tachinid flies over-winter as pupae in the long-dead shells of their beetle hosts, then emerge as adult flies during early June. * Adults
feed on the products of flowers, locate a mate, then immediately begin the
search for an appropriate host (mostly newly-emerged beetles) upon which to
firmly glue from one to three eggs. * Each female tachinid can deposit about 100 eggs over a fourteen day period. Deposited eggs hatch within 24 hours and the tiny “maggot” quickly burrows into the beetle’s abdominal cavity and begins to chow-down. * The now-parasitized beetle almost immediately falls to the ground and buries itself, where it perishes in a few days (compared to the normal 28- to 40-day destructive lifespan of non-parasitized beetles). * A few days after the host beetle dies, pupation (the next step in tachinid development) occurs, a stage that generally lasts about 1-1/2 to 2 weeks. . .followed immediately by a second generation of these beneficial predator flies. * Newly emerged adult tachinid flies begin the sequence all over again until cooling fall weather signals the last generation of the season to remain in the ground until the following spring. There are a great many types of tachinid flies that “specialize” in the parasitizing of a wide variety of insects including caterpillars like cabbage loopers and moth larvae and, of course, beetles. Field studies have consistently shown that from 40 to 50% of Northern New England Japanese Beetle populations are currently being parasitized by this very efficient little fly. So, follow these two very important new “rules”: If, while scouting your garden for Japanese Beetles, you see some with small, 1 mm whitish dots glued just behind their heads (see photo above), don’t — repeat: don’t — destroy them. I know that’s going to be difficult for most gardeners, but it’s been shown that those beetles will almost immediately fall to the ground to be quickly destroyed by an even more aggressive foe than us. . .and those beetles will never have the chance to lay any more eggs or harm your cherished plants! Also important is avoidance of toxic chemicals — or even natural insecticides — that might destroy or hinder the highly-desirable activities of any outdoor, nectar-feeding fly. Let’s all work hard to keep a good thing going! |
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Researchers at North Carolina
State University have learned that Japanese beetles will avoid eating leaves of certain
varieties of Prunus trees, cherries and related species, which contain high
levels of the chemical, prunasin. When Japanese beetles eat plants with high prunasin
concentration, these enzymes cause prunasin to convert to cyanide. While the levels of
cyanide are not enough to actually kill beetles, it certainly acts as a repellant,
discouraging further feeding. This information could very well lead to the development of
plants, other than cherries and prunes, having stronger resistance to this pest. Who
knows, it might even lead to a natural pesticide or repellant derived from the leaves of
cherry trees! I'll watch future research and keep you posted.
