Garden Notes: Dogwood Sawfly produces headaches for gardeners
One of the best garden books I have is “Bloom’s Best Perennials and Grasses” by Adrian Bloom. It shows a picture of a striking winter container: a red twig dogwood bush with an under planting of black mondo grass; and to complete the composition, snowdrops sparkle between the two plants.
Intending to follow Mr. Bloom’s example, I bought two red twig dogwood bushes. I planted them in the biggest containers I could find, and they grew on either side of the front door. They were a cheery red throughout the first winter and produced barely-there white blossoms and ho-hum leaves in the spring. Year-round container plants are particularly vulnerable to the cold winter temperatures we’ve had this past winter, so I’m looking for signs of life now.
Actually, I’m looking for two signs of life. Leaf buds and caterpillars. I wish Adrian Bloom would have clued me in on Dogwood Sawfly! Last summer, I started to notice that something was chewing the leaves. I turned over a leaf and found what looked like a nest of some disgusting looking caterpillars. It seemed every leaf had a squirming mess of six or eight caterpillars. First, I hit them with insecticidal soap, and when that was too polite for them, I started picking the scraggly leaves off and stomping on them. Just about the time I thought I had them all, they’d come back.
Dogwood Sawfly is a native pest resembling a wasp. The adults emerge as early as this month and insert their eggs into the dogwood leaf tissue. In summer, the larvae go through a number of growth stages. At every voracious stage, they eat the leaves between the veins and eventually leave only the midrib.
Sometimes wasps or hornets attack the larvae. They actually chew it in half and then fly it back to their nest. I usually don’t roll out the welcome mat for wasps and hornets, but I’ll make an exception to get rid of the Sawfly. After their last molt, they stop eating and start to look for somewhere to spend the winter. They prefer rotted wood. The following spring, they emerge as adults and start the cycle again.
Here’s the good news. Dogwood Sawfly produces just one generation a year, so if I find any and manage to eradicate all the larvae this spring, I won’t have to deal with them the rest of the summer. And even if they manage to sneak by me and chew all the leaves off the bushes, I’ll still have the red twigs. The Dogwood Sawfly doesn’t harm the plant. Just my aesthetic sensibilities.
* May 13, 11 a.m., Pollinators, a Master Gardeners program, Northern Blair Senior Center, 505 3rd Street, Tyrone
* May 16, 9 a.m. to 5 p.m., and May 17, 9 to 11 a.m., Blair Garden Club sale, Dorman’s Jewelry, 712 Pleasant Valley Blvd. Altoona
* May 17, Tyrone Garden Club’s plant sale, Tyrone City Park, 8 a.m.
Contact Teresa Futrick by e-mail at email@example.com