I did pest control a few years ago - mostly commercial (packing houses, restaurants & grocery stores).
Given your environment (micro-agricultural), I'll take a guess at fungus gnats.
Here's a description and a link if you want to know more.
<p><strong>Drains can build up sludge that attracts fruit flies and drain flies. TERRO<sup>®</sup> has solutions for dealing with both of these pests.</strong></p> <p>When your home is under siege by tiny
www.terro.com
HOW TO ID FRUIT FLIES
Without a doubt, fruit flies are the most common flying insects that will pester you in the kitchen. They are attracted to fresh and decomposing fruit as well as sugary juices and alcohol.
- Colors: The two most common fruit flies, the Red Eyed Fruit Fly and the Dark-Eyed Fruit Fly, have striped abdomens. Their eye colors are, as the name suggests, red or black, respectively.
- Size: Red Eyed Fruit Flies are about ⅛-inch long. Dark Eyed Fruit Flies are a bit bigger, at about 3⁄16-inch long.
- Body type: Similar to a house fly, but much smaller.
- Where: Fruit flies may be buzzing around your fruit bowl, inside a trash receptacle, in a recycling bin or in your drain or garbage disposal.
HOW TO ID FUNGUS GNATS
If you spot a swarm of bugs flitting above a houseplant, you probably have fungus gnats instead of fruit flies. Fungus gnat larva and pupa prefer moist soil to protect them as they develop. Before they progress to adult form, they can severely damage the root system of your potted plants.
- Colors: Adults - brown or black with light colored legs.
- Size: Adults are less than ⅛-inch long. Their larva and pupa forms are about the same size.
- Body type: Although they are technically flies, they have a mosquito-like appearance.
- Where: Fungus gnats will be spotted flying close to your potted plants and will show little interest in going anywhere else as long as there is moist soil available.
HOW TO ID DRAIN FLIES
These hairy bugs are another kitchen pest. They thrive in dark, damp conditions and often find an ideal home inside a drain, which can include a floor or a sink drain, sink overflow or another area open to plumbing. Although they don’t bite, their presence can aggravate asthma in some people.
- Colors: Light gray or tan with a dark border around wings.
- Size: About ⅛-inch long.
- Body type: Moth-like with fuzzy bodies and antennae.
- Where: Drain flies breed inside of drains, often laying eggs in the sludge that accumulates inside. Adults will clumsily fly out of the drain and land nearby on walls and ceilings.
**** Just realized that the link is a pest control site - just my $.02 ---
1. Be
VERY wary of "organic" pesticides. Being in California, most of my chemicals were organic. The two most lethal chemicals onboard the companies vehicles are both organic - I was required to wear a full-face, double cartridge respirators and a tyvek suit and practiced real decon procedures in my garage after those days.
2. MANY safe options available, but be aware that most will take a bit of time to work fully. Avoid spraying pyrethrins (chrysanthemum flower derived) or other chemicals if at all possible