Question
I live in Council Bluffs, IA.  I have several Hibicus trees which I have kept for a number of years.  I put them outdoors in the Spring, and bring them in before frost in the Fall.  The problem I have is house flies!  Every year, late Winter I am bombarded with them!  I assume the must be from eggs laid in the soil.  Issues #2 and #3, I have exotic birds, so I can't bomb the house, and I have a small child.  Is there anything I can water into the soil to kill the flies, larvae, etc.  I use the Prozap Insect Guards and they do work for a few days.  They don't harm the birds, but are a bit unsightly.  I had used Diazinon in the past, but I understand it's been removed by the EPA.  Any other suggestions?

Answer
flies(and larval maggots) are a sign of keeping the soil too wet. they breed in wet soils. let your plants dry out sufficiently between waterings. water by weight. put a saucer under the pot. water and let the plant sit in the excess water for 5-10 minutes. after that time pour off any excess water in the saucer. pick up the pot. it should feel heavy. don't water again until it feels considerably lighter in weight. the soil will be light in color/not dark and wet. outdoors check the plants everyday. indoors check it every 5-10 days. watering frequency depends on many factors(sun exposure, wind, day temps, etc.).
you could buy a safer soap pesticide(professionally formulated) and apply it as a soil trench. they make yellow sticky plastic cards to put near the plants to attrack the adults. you could sprinkle a teaspoon of turf lime over the soil to sweeten(raise the soil pH) of the soil. acidic soils attrack gnats & other flies.
get to a local garden center/nursery and quiz them on a solution to your problem. buy your products from them and they should be more than happy to help you.
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