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The Fungus Didn't Get Them First; Invasive Caterpillars Defoliating Trees

A fuzzy gray and black caterpillar sits on a raspberry leaf.
grannyogrimm
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The invasive Lymantria dispar munches on a raspberry leaf. The caterpillars can defoliate oak and maple trees during a summer season.

As the hot sun beats down and afternoon rain showers quench our gardens, up in the canopy of our hardwood trees, an invasive species is having a field day.

The species formerly known as the gypsy moth caterpillar is back with a vengeance.

Its Latin name is lymantria dispar dispar or LDD, and these critters are decimating leaves in our region. The LDD favor the leaves of oaks, maples and apple trees along with all kinds of different deciduous trees.

Listed as one of the hundred most destructive invasive species in the word, its larvae consume the leaves of over 500 species of trees, shrubs and plants and you may be noticing them in your trees right now.

Most years, a fungus in the atmosphere kills the larvae and keeps them in check. However, the weather this spring may have favored the caterpillars over the fungus.

There are some techniques to combat the crunching, munching LDD caterpillars. And if you have healthy, older and established trees, they will probably weather the caterpillars just fine. 

The trees you really want to protect from these invasives are the ones you may have just planted this spring. 

The method to combat the critters is a simple one: use soap and water.

In the morning or evening, go out to your trees armed with a pail of soapy water, then simply pick them off the leaves and tree trunk and knock them into the pail.

You can try another trick to trap the critters: wrap burlap or sticky tape around the tree trunks. This method can help trap and gather the caterpillars and then you can shake them into that soapy water.

Q: My phlox all have black spots and yellowed, dropping lower leaves. I removed the bad leaves and sprayed them with baking soda and water last week and still have spots. Then a gardener said to spray with a 1:2 ratio of hydrogen peroxide to water, which I did yesterday, but I am worried that the disease will spread everywhere. — Kate, in Jamaica

It's not unusual to have the black spots on phlox, especially during humid weather. The yellowing of the phox leaves could be caused by powdery mildew, which phlox is known to get.

You might try another flower variety that is more disease-resistant, like David phlox.

If you are going to spray something on your phlox leaves, the baking soda spray is a good choice. There is also an organic spray called Serenade, which is a bacteria that fights the fungus.

And both baking soda and the fungicide work best as preventive sprays. Use them early on, before you see signs of the damage and they'll help keep the plants healthy.

Q: I'm interested in flowers that attract bees in the narrow space between my house and the neighbor's next door. It only gets direct sunlight for an hour or two each day. This spring I picked shade wildflower seeds to scatter. My only concern is getting stuff to grow for bees. — Robyn in Denver, CO

If you have a shady spot, you can still grow a bee garden! 

Some options that do well in shade or part shade are flowers like bleeding hearts. Lamium is another great choice, as its a ground cover that flowers early and thrives in shade.

You can also plant coral bells and hellebores, which is an early-flowering plant and perennial. Some other great choices that do well in shade and that bees love are companula and ligularia, which is a summer- and fall-blooming flower.

Get the right plants for your shade garden and you'll support the bees, as well!

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All Things Gardening is powered by you, the listener! Send your gardening questions and conundrums and Charlie may answer them in upcoming episodes. You can also leave a voicemail with your gardening question by calling VPR at (802) 655-9451.

Hear All Things Gardening during Weekend Edition Sunday with VPR host Mary Engisch, Sunday mornings at 9:35.

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