Growing certain plants in the garden can attract good bugs, who in turn eat the bad bugs. I don't spray anything in the garden and nature does a great job of dealing with pests and diseases.
Planting dill is one of the best ways to bring in the good guys. Most small flowering herbs like oregano, basil and thyme will atrract good bugs. By not using systemic pesticides of any time, you let nature do the work for you and you'll be surprised how well the garden can take care of itself.
As I mentioned in yesterday's post, letting a corner of the garden grow wild offers habitat for beneficials. Cover crops planted at the end of the season, like winter rye will also attract good bugs. The cover crop will also add fertility to the soil the next season when it's dug under as a green manure.