Hi, I just spotted your question. There is an easy organic solution to your question which is always 'put down' by those who know everything. For a planter...mix 1 cup of fresh, uncooked coffee grounds with 1 cup of granulated sugar. Work this combination into planter soil surface and water well. Easy. Try it. An old method that was commonly used in the Victory gardening days to treat any plant prone to nematodes. If planting carrots, etc. run this sugar/coffee combination down the planting row then plant and cover seeds.