Pre-treatment of tropicals BEFORE bringing them in for the winter

Last year I brought all my tropicals in to work when the night temps dipped below 55*F. A few days later the office became plagued with gnats. I'm looking for a proper pesticide to apply to the trees (specifically the root mass) to kill off larvae and prevent a repeat of last year.

(Especially, since most of the tropicals will migrate to MY basement for the winter instead of work.)

One nursery suggested some granuals (can't remember of what) but advised using them outside before bringing them in.

Any suggestions?

forbey

At our club's spring auction I purchased a neea buxifolia which came with little black gnats... soil may be too damp. I found yellow sticky paper at the garden center which when put in pot attracted the gnats. End of problem !!

Good luck!
Norma

I also found a product called "Gnatrol", on line, it is a specific variety of Bt (Bacillus thuringiensis). It's a nasty little nematode that is ingested by the pest and proceeds to eat all the hosts food, resulting in larvae starving to death. It is applied as a drench. I probably need to find some more.

The sticky yellow traps were somewhat effective, but did not solve my problem last year.

forbey

There are many tropicals that prefer being left out until the temperature goes into the 40s, or some until a frost warning.
Bacillus thuringiensis is a bacterium, not a nematode.
Fungus gnats (black flies in UK) themselves are a nuisance, but not particularly dangerous to bonsai. The larvae feed primarily on decaying organic matter, but may damage roots. Fungus gnats are a canary, an indication of an unhealthy situation which may lead to root rot. They mean you have too much organic matter in your soil, or it is the wrong kind. You should avoid peat moss, Michigan peat, compost (US definition), or any highly decayed or finely ground organic matter. Chopped pine bark or fir bark are recommended, sifted to remove the dust. Since I can't tolerate breathing dust, I wash all my potting components in a strainer or colander.
Overwatering may be a factor, but bonsai in well-drained soil tolerate frequent watering or rain. Any soil insecticide just before you bring your plants in will take care of the situation temporarily, but if necessary, they should be repotted to prevent fungus gnats.
Iris

I stand corrected on the nematode vs bacterium issue. It's been a while since I read over the info on the Bt. If looking for the proper variety of Bt for black flies, gnats, etc. find a treatment with Bti (Bacillus thuringiensis subspecies israelensis) The USEPA Fact Sheet for Bti is located at:

http://www.epa.gov/pesticides/biopesticides/ingredients/factsheets/factsheet_006476.htm

Gnats were not a problem for my trees, they did however, make me fairly unpopular with my co-workers.

We did survive the infestation.

I simply want to take out the pests before I tick off my co-workers.

Thanks for the info, Iris.

forbey