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Dealing with gnat-infested potting soil, moles

Fungus gnats are commonly carried home in packaged

Fungus gnats are commonly carried home in packaged potting mix.

Dear Jessica,

We recently repotted a houseplant with new potting soil. A short time later, we noticed tiny, flying bugs in the soil and in the house. Please help.

Theresa Graff, Holbrook

Dear Theresa,

The potting soil you purchased likely was infested with fungus gnats -- or their eggs. This is a fairly common occurrence, unfortunately, and no one brand of potting mix that I'm aware of is better than another in this regard. There are only two ways to avoid any chance of introducing fungus gnats when repotting: Purchase sterile potting mix (it will be noted on the bag, but may be difficult to find at this time of year because it's usually used for seed starting) or sterilize potting mix yourself by cooking it in the oven.

Sterilizing soil not only kills insects and their eggs, but also seeds, fungus and bacteria. In a pinch, used potting mix (which otherwise should never be reused) and even garden soil can be sterilized in the oven. Be forewarned, however, as there is a downside to this method: It will stink up your house.

To sterilize soil in the oven, spread it to a depth of four inches or less on a baking sheet or roasting pan, and cover tightly with heavy duty aluminum foil. Insert a meat thermometer through a hole in the foil into the middle of the soil. Bake at 180-190 degrees (higher could damage the soil and make it inhospitable to plants). When the internal temperature indicated by the thermometer registers 180 degrees, bake for 30 minutes longer.

Since it's too late in this case, the best thing to do now is dump the soil, rinse the plant and roots with water and clean the pot with a 10 percent bleach solution, then repot with fresh potting mix. Hopefully the next batch you buy will be gnat-free. Use yellow sticky tape traps to eliminate any gnats that remain in the house and prevent them from laying eggs in your new soil and starting the cycle all over again.


Dear Jessica,

Are moles active all year? On Dec. 14, my lawn and my neighbors' lawns were loaded with moles. Our neighborhood has a lot of construction going on, with woods being dug up and cleared. The moles are now in our yards. I tried pellets that didn't work. I bought Molemax Sonic Spikes, which seemed to work but I took them out for the winter because they run on batteries, which would be drained by cold temperatures. How can I eliminate them?

Vincent Ewart, Riverhead

Dear Vincent,

Although spring, summer and fall are seasons of higher activity, moles can, in fact, be active all year. It seems the construction in your neighborhood has displaced them and led them to seek new homes in your and your neighbors' yards.

The good news is you aren't likely infested. Moles are loners by nature, so you likely only have one or two at the most. These critters have voracious appetites and can consume about 70 percent of their body weight in grubs and insects each day, tunneling through as much as 100 feet of lawn in the process, leaving volcano-like mounds in their wake. They don't eat roots, bulbs or any other plant parts, but do disturb them in their quest for food.

If you're a glass-half-full kind of person, you might appreciate knowing that mole activity can actually be beneficial: It aerates soil and keeps it loose, which supports healthy grass and root sprawl, and the furry little critters can keep your soil free of grubs and other harmful insects like Japanese beetles. Still, it's understandable if you don't want holes and soil mounds wrecking the lawn you no doubt poured your blood, sweat and money into all summer long.

There are all manner of controls available, from fumigants and baits to insecticides aimed at eliminating grubs and, thus, killing off moles' food supply. None are especially effective, and some are harmful to the soil, environment, humans, pets and/or wildlife. I'm not aware of any data supporting the use of mechanical deterrents like the sonic spikes you mentioned, but if you've had success, then take advantage of them for as long as you can before snow deems them ineffective or impractical. Your only other recourse, which also is the most effective, would be to trap them. There are several traps on the market that will eliminate your mole, but with ongoing construction in the area, my guess is another will soon take its place.

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