Hand-pick dogwood sawfly larvae to stave off an infestation safely

Backyard Q&A

In the Garden

August 29, 2004|By Jon Traunfeld & Ellen Nibali | Jon Traunfeld & Ellen Nibali,Special to the Sun

Two weeks ago, I thought I saw bird droppings on my red twig dogwood. They turned out to be caterpillars with a powdery white coating. More were curled under the leaves. Now my shrubs are being defoliated at an alarming rate. The caterpillars have stripped four shrubs. We hand-picked them and dropped them into a bucket of water and noticed more caterpillars that are green with black markings. What I can do to salvage what little remains of the shrubs? Should I cut them to the ground?

All the "caterpillars" defoliating your dogwoods are dogwood sawfly larvae, not true caterpillars but the immature stage of a wasp. They go through several molts, and at the final one they lose the original white covering and are greenish yellow with black spots. Handpicking is the safest way to go. In spite of defoliation, your dogwoods should be fine next year. There is no need to cut them back. Next year, monitor the plants beginning in June. At the first sign of damage and / or sawflies, pick off the sawfly larvae and dump them into soapy water. Large numbers can be sprayed with insecticidal soap. See our publication "IPM Series: Dogwood."

I need a positive identification on a plant similar to a currant or blackberry. It is taking over several wooded hillsides on my farm. How can I get rid of it? The stems have a reddish color and sharp spines.

If this plant produces pink flowers followed by red fruits from June-September, it is wineberry, Rubus phoenicolasius. Native to China, wineberry is also distinguished by its many fine, almost soft-looking prickles on the stem. (Our native raspberry has coarser prickles with a blue-green stem in the summer and a lavender stem in the winter.) Wineberry is proving to be invasive in Maryland. Eradicate by hand-digging or using a herbicide with the chemical Triclopyr.

Which vegetables can I plant this time of year? I was told collards, kale and cabbage are OK. Is there anything else?

All greens in the cabbage family and Asian greens can be grown now, including cauliflower and broccoli, also turnips, carrots, beets, corn salad, radishes, lettuces, and spinach. Keep seedlings and transplants well watered and mulched.

Spinach and lettuce seeds may germinate poorly in warm soils and should be sown heavily to compensate. Keep in mind that fall vegetables require more time to mature because of reduced sunlight and ambient temperatures. Add at least two weeks to the "days to maturity" number on your seed packets.

Covering your seedlings with a floating row cover will help you extend the season into November and December. Our publication HG#16 gives planting dates for spring and fall.

Checklist

1. It's a good time to build cold frames and other season extenders.

2. Identify lawn weeds. Fall is an excellent time to apply herbicide to perennial weeds.

3. Iris can be divided now and foliage can be trimmed and neatened.

Jon Traunfeld, regional specialist, and Ellen Nibali, horticulture consultant, work at the University of Maryland Cooperative Extension's Home and Garden Information Center. The center offers Maryland residents free gardening information and answers to plant and pest questions. Call its hot line at 800-342-2507 (Monday through Friday, 8 a.m.-1 p.m.) or e-mail questions to www.hgic.umd.edu. (You can also download or order publications and diagnose plant problems online.)

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