Depending on what you're growing and what "buggs" are eating your plants, you can go the bio way by growing certain other plants along side your vegetables to keep them away.

As far as fungus, you could be over watering, usiing contaminated soil?? Easy solution is to buy organic compost from your local seller (supermarket/farmers market) and add keep a close eye on the soil conditions.

I try and keep my garden as organic as possible too and it's a constant fight keeping on top of it all.