Q&A: Drain flies, powderpost beetles, honey bees and gnats

Photo: ©istock.com/JaruekChairak

Q: In a hospital sterile area, a janitorial closet has a drain fly problem. A vent stack for the drain system opens about 4 ft. above the floor. The elbow (trap) is dry. I shouldn’t use any pesticides in this area, but I can’t close off the stack. How can I solve this problem?
— Rick S., Maine

A: Because the trap is dry, the stack above the trap should not have any slime growing in it to support fly breeding. If there is any organic matter there, clean it out with a brush. Then fill the trap with water. I suspect the flies are breeding farther down in the stack and exiting in this closet. After you fill the trap with water, pour in several ounces of oil (any kind). The oil will lie on top of the water and slow or prevent evaporation, so the stack will not need to be refilled very frequently.

Q: I inspected a log cabin home with an Anobiid powderpost beetle infestation in the logs. The infestation is scattered in many areas. I considered a borate treatment, but the logs have all been painted. Can I still use a borate? What are other options for dealing with this infestation?
— Mike G., New Hampshire

A: You are correct: A borate will not penetrate a painted surface. Your options are removing the paint (perhaps by sand blasting), or fumigation. If you’re considering fumigation, take moisture readings first. If the wood is high in moisture — approaching 20 percent — the fumigant may not penetrate sufficiently to provide kill. I have had several such fumigations fail because of high moisture content.

Q: A customer has honey bees working their way up beneath a slate roof. There is no access inside to reach the area in question. Because bees are protected, is there anything I can do to help?
— Joann T., New York

A: Ask the homeowner to contact a beekeeper to remove the bees. The bees probably are setting up house and building honeycomb and making honey. Sooner or later, this will lead to other problems, such as staining from the honey or scavenger beetles of various types invading to feed on the honey.

Q: We are finding fungus gnats in a bank. An inspection of potted plants did not reveal an infestation. Where else should we look?
— John D. Delaware

A: Obviously, you are looking for a moisture source. I can think of two possible sources in a bank:

1. The roof. If there is a drop ceiling, pop some tiles to see whether there are any fungus gnats. If the bank had a roof leak, find out when it was repaired and whether the roofer removed all of the wet organic materials under the roof membrane.
2. The vault. Most bank vaults are constructed of two thick, metal shells — one outside and one inside. Between the two shells is wood to hold the shells apart.

If one or more walls of the vault is on an outside wall, condensation can occur between the two shells.

A vault company will need to drill holes in the bottom to permit drainage.

Email your questions about insect identification and pest management technologies and techniques to Dr. Mampe at dentomol@aol.com. Your questions most likely will be printed and answered in one of Pest Management Professional’s upcoming Ask the Expert columns.