I was just reading my new old farmers almanac and came adross this article. They certain plants and herbs keep away certain bugs so I'm passing it along. I edited out plants that I would never have in my garden because they are either too invasive and could become pests. So here's the list

basil------flies, hornworms

borage-----tomato hornworms

catnip-----aphids, flea beetles

flax-------potato bugs

garlic-----japanese beetles

leek-------carrot flies

marigold---mexican bean beetle,nematoids

nasturtium-squash bugs, striped pumpkin beetles

rosemary---cabbage moths, carrot flies,mexican bean beetles

sage-------cabbage moth, carrot flies

tansy------ants, japanese beetles, stripped cucumber beetles

thyme------cabbage worms

I don't know how effective these are but it would be worth a try.