Thorough repotting may help get rid of fungus gnats, shore flies

Your Maine Garden

Q. A Columbia reader has written to ask for help with a minor plague in her house. She first noticed the tiny black flies rising from some of her house plants, then she noticed them in a bag of onions and also in the bathroom. Last spring the flies were rampant in flats of seedlings that she started indoors.

A. This is the second query I have had recently concerning these not-uncommon pests. The other person had so many of them that they would occasionally land in the coffee cup or cereal bowl in the morning.

Without seeing the bugs, I cannot positively identify them, but it’s a safe bet they are either fungus gnats or shore flies. The two insects have similar habits, feeding on the algae and fungi that grow on the surface of the soil in our plant pots. They are attracted to moist environments, which explains their migration to the bathroom and the coffee mug.

Both types of flies breed relatively quickly at indoor temperatures and lay their eggs in the soil. These soon hatch into larvae, tiny white maggots, that burrow in the soil and occasionally invade the roots of some plants.

Getting rid of fungus gnats and shore flies can be difficult, speaking as a greenhouseman who has not fully succeeded at the task in several years of trying. I would recommend that homeowners with a serious problem think about repotting all their plants at one time, taking great pains to remove as much of the old soil from the roots as is humanly possible. After shaking the roots vigorously, rinse them in a buck of tepid water. Make sure that all the old soil is quickly removed from the house. Use sticky yellow card traps to trap adult flies, or try killing them with a soapy water spray when you see them flying about.

For more information and a positive identification, contact the University of Maine’s Pest Management Office at 581-3880.

Q. An Ellsworth reader received a gift of six seeds from a plant identified only as Mirabilis, “Queen of Peru.” She was told to plant them indoors in January and set them out after the weather turns warm.

A. I must confess that this one sent me to the reference books, where it quickly became clear that the seeds must belong to an old-fashioned annual called four o’clock, a name which commemorates the plant’s interesting habit of opening its blossoms in the late afternoon. Marvel of Peru is the other officially recognized common name.

January would be about three months too early to start four o’clocks for setting out on Memorial Day, since the plants grow two feet tall and become rather bushy. Better to wait until the middle of March and give the vigorous seedlings as much light as possible.

Q. A Dixmont gardener wants tips on collecting greens for holiday decorations, specifically which types of evergreens to use and which to avoid.

A. Balsam fir (identified by its Christmasy smell and the two pale green stripes on the back of each short needle) is the backbone of the wreath and swag industry. Use pruning clippers to snip the last 12-18 inches of branches that have a nice full look.

Cedar tips contrast nicely with balsam, lending a different texture as well as shade to your arrangements. And let’s not forget our state tree, the white pine, which gives a bold touch to garlands and swags.

Avoid spruces, especially white spruce which can be smelly if brought indoors. Look for the still clinging red berries of highbush cranberry and turkey berry for native holly substitutes.

Greens used for table arrangements or other inside decorations will dry out very quickly unless they are in water. When dry, they pose a considerable fire hazard especially with lighted candles nearby.

One last note, Sunday is the safest day to be in the woods and blaze orange wouldn’t hurt a bit.

Michael Zuck of Bangor is a horticulturist and the NEWS’ garden columnist. Send inquiries to him at 2106 Essex St., Bangor, Maine, 04401.