Neem oil is good. Helps in a lot of cases for all sorts of reasons.

If the ground stays too wet for too long your going to drown the roots and be plagued by rot and fungus. A trick from a friend who grew his crops in a swamp, what he was growing and why it was in a swamp isn't important, used to grow his plants in five gallon buckets with the bottom cut out. This raised his plants up a good fourteen inches so they still did okay and didn't drown if the land was under half a foot of water for a week.

With the bottom of the bucket cut out when the roots needed more room they had somewhere to go.