If you have gnats increase the acidity of the soil with lemon juice or lime juice or better yet coffee grounds which provides nitrogen also. I learned this with my worm castings when the soil is alkaline gnats thrive. Also patchouli, cedar wood, peppermint works.
Here is a list I have compiled of natural pest controls from various sources. Unfortunatley I can not take credit.
Ants: peppermint, coffee
Aphids: cedar wood, peppermint, spearmint
Beetles: peppermint, thyme
Cutworm: thyme sage
Fleas: peppermint, lemon-grass, lavender, rosemary
Flies: lavender, peppermint, rosemary, sage
Gnats: patchouli, cedar wood, peppermint
Lice: peppermint
MITES orange peel and extract ingredient of neem oil - azadirachtin
Mosquitoes: lavender, lemon-grass, eucalyptus, cypress, lemon, orange, cedar wood, peppermint, geranium
Moths: cedar wood, peppermint, lavender, and even a glass of wine
Roaches - Baking soda and powdered sugar mixed in equal parts
Slugs: cedar wood. Fir (pine)
Ticks: clove, lemon-grass, sage, thyme
Weevils: cedar wood, patchouli, sandalwood
Cucumbers are a natural and generally non-toxic way to repel or get rid of bugs including ants, wasps, mites, moths, flies and other insects.
Barriers act like barbed wire to keep crawling pests, such as ants, out. These include garlic - grind it up with water and apply - cayenne pepper, cinnamon, powdered charcoal, bone meal, talcum powder or chalk. Keep in mind that different pests have different aversions, so you'll have to see what substance works best with the ones trying to sneak into your home.
Diatomaceous earth is made up of the fossilized remains of diatoms, single-cell organisms. The glass-like nature of diatomaceous earth makes it one of the oldest forms of insecticide. The sharp surfaces cut through the insect cuticle and the insect dies of dehydration. Diatomaceous earth kills earwigs, ants and box elder bugs. Since it's non-discriminate when it kills, be sure to only apply it just to the ground surface where you think insects are overstaying their welcome.
A natural fly catcher related to wine is to put something sickly sweet like mango peels in the bottom of narrow-necked wine bottles. The flies can fly in, but can't fly out.
You can even make your own fly paper. Boil water, sugar and corn syrup together. Spread the extra-sticky mixture on brown paper grocery bags and voila you have your own fly paper which will trap flies.
Vinegar is a great herbicide. Fill a spray bottle with vinegar - white is best since it won't stain; you certainly don't want to use expensive, aged Balsamic vinegar on weeds - and spray the vinegar on your unwelcome flora on your porch, patio or back yard. It's one of the few things that will work against noxious weeds such as Canadian Thistle. All vinegars are diluted, so try and buy the highest concentration you can at the supermarket.