I received this question recently.
“Yesterday, while watering the plants (which are thriving) I noticed there were small bugs that flew out from under the lid. They were very small and hard to notice at first yet, I am not sure if we should be concerned. Lately at our school we have been having fruit fly problems, so the teachers used a small cup of vinegar to try to get ‘rid of them. Is that something we should try? If you have any advice or information for our bug problem, please let us know. ”
Here’s my response.
First off, if the plants look like they are thriving, you may not have to worry over a few bugs.
On the seedlings I raise in the basement, I do have problems with small gnat type flies and also white flies. If I didn’t do anything, the population would get out of control.
Yellow sticky traps. These are very effective with the flying insects, but less so with white fly. This might also help with the fruit fly problem at the school.
My second method is to use a shop vac with a soft bristle and simply vacuum the plants and remove the bugs mechanically. Be gentle with the plants.
My third method is to use Safe Insect Killing Soap. I have had good results with this spray and it should not have any residual effects when you put the plants outside. You could also try a horticultural oil spray which should be safe to use.
With the above, first test the spray on one plant to make sure it doesn’t hurt the plant.
I would not use anything stronger than the above methods.