What is the difference between contact and systemic fungicides?
Contact fungicides remain on the leaf surface, acting as a shield. They only provide a barrier to protect against infection so they must be applied before infection and very completely. Systemics penetrate the plants skin to the layers under the bark or the leaf surface. However there are different kinds of systemics. Some penetrate but do not move far. These are locally systemic or Mesostemic fungicides that bind the waxy layers that protect the plant. They move across the leaf some but not into the vascular tissue. http://www.farmline.com/folcorps/novarti… Others penetrate to the vascular channels. If the systemic enters the xylem it moves out to the leaves to protect the ends of the leaves. This is an acropetal penetrant. Since they move they must be reapplied more frequently. Terms for fungicides
