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Blister beetles and baby stink bugs

Friday - 8/5/2011, 10:35am  ET

  • Gallery: (2 images)

New stink bug trap 'the bee's knees'

Mike McGrath, Garden Plot

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Blister beetles: a dangerous garden pest

Gwen in Purcellville e-mailed a photo and this message: "Can you identify this pest that's been decimating my tomato plants? I've been handpicking them, but I have to leave for a few days and I'd hate to come home to nothing but a pile of bug poop."

Gwen's photo clearly shows a blister beetle, a very dangerous farm pest (just one beetle in a load of hay can make a horse dangerously ill if the horse eats it). The beetles sometimes migrate into nearby gardens when farmers cut the hay the beetles were infesting.

They are voracious plant eaters, and as their name more than implies, because of the nasty blisters they cause when they're crushed. (I e-mailed Gwen about this. She explained that she was, thankfully, wearing rubber gloves when she was picking them off her plants.)

Spray the beetles and the plants they're attacking with an organic insecticide whose active ingredient is neem or one of the spinosads. Any beetles that eat the sprayed leaves will die-with little to no potential harm to you or the environment.

If it's an emergency situation like Gwen's and there's no time to seek out such a product, spray them with Pam or one of the other aerosol no-sick cooking sprays. They're essentially the same as a light horticultural oil spray. (But, as with any soap or oil spray, you must coat the pest for the spray to be effective. Just spraying the leaves won't protect the plants.)

And listeners, if these beetles appear in your garden, be very careful not to touch them with your bare hands; they're real bad actors.

Baby stink bugs look different

It's dirty picture week here at the Plot! Kat in Leesburg writes: "I noticed that my Petite Pepper plant was developing spots, checked it carefully and noticed the pest whose photo I've attached to this e-mail. I have been unable to identify it, so I used an organic spray that only kills pests on contact. It worked but new ones appear within hours. Can you help?"

Sure thing, Kat. Your photo clearly shows a stink bug in its juvenile stage, before it develops that distinctive shield shape we're so used to seeing. This is a great use for the new Rescue stink bug trap that recently went on sale at garden centers throughout our area-it's designed to catch all stages of the stinkers, including this otherwise hard-to-control juvenile delinquent.

Here's a link to more information, including a list of area retailers who are carrying the traps and lures.

Those aren't pine cones. They're caterpillar condos

Barbara in Stafford tersely writes: "Bagworms on Leyland Cypress trees! What do you do and when?"

First, congratulations on noticing this well-camouflaged pest, Barb. Bagworms spin cocoons that are almost identical in appearance to the pine cones that commonly appear on the evergreens they attack.

Now, the silk they use to attach those cocoons to evergreens is stronger than Spider-Man's webbing, and can girdle the branch it's on. So first, prune off (and, of course, destroy) any bags you can reach. Don't worry about cutting off the branch tips. It's much better for the tree's long term health than leaving those bags on.

Then spray the tree every 10 days or so with the organic caterpillar killer Bt. Also known as "BTK", it's sold under brand names like Dipel (the most common brand name), Thuracide (also widely available at retail) and Green Step (the brand sold by the all-natural mail order firm Gardens Alive). Bt is wonderfully selective, and only harms caterpillars that chew on the sprayed plants. It'll kill any of the bagworm caterpillars that try and feed on your tree without any risk to people, pets or the environment.

Lots of cicadas = lots of cicada killers

Sandy in Vienna writes: "Year after year it seems like hundreds of Cicada Killer wasps invade my yard. I know they'll be gone in a few weeks, but what can I do to get some relief now? And how can I keep them from coming back next year?"

Well, Sandy, you may be seeing a lot more of these large wasps than normal because we're in the middle of a big cicada brood emergence. You can hear the noisy creatures everywhere. As you know from your years of experience, these big wasps look fearsome but they don't sting us humans, so just let them be for now. They're protecting young plants (especially fruit trees) by picking off some of the cicadas that would otherwise feed on the young plants.

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