Fungicides should be used only when other approaches to disease control have failed. Two types of fungicide are used, protectant multi-site inhibitors and systemic single-site inhibitors. Protectant fungicides are largely based on copper and have been in use for many years. Such fungicides are highly effective in control of foliar diseases even during wet weather, but application is necessary at 7-10 day intervals. Protectant fungicides are also ineffective in control of diseases such as stem cankers, where the fungicides is protected from contact by the dark.