PLPA 2010 1st Edition Lecture 11Outline of Last Lecture I. Rust FungiOutline of Current Lecture II. Plant Diseases III: TreesCurrent Lecture- Tree Diseases:o Chestnuts:  Lots of chestnuts in America in 20th century Cryphonectria Parasitica: fungus introduced from Asia, where it doesn’t cause much trouble. Makes a canker in the tree that girdles and kills the tree. Can reproduce sexually (genetically diverse, faster)/asexually Deadly to our American chestnuts Blight spread rapidly from the east coast in It got just about everywhere by the 1940’s (ecological catastrophe) 4 billion trees died within 40 years There are still chestnuts around here, sprouting from stumps dead almosta century but they rarely get big enough to fruit For the last 70 years, scientists have been trying to breed a resistant chestnut tree. Interbreed Asian and American chestnut treeso Tar Spot: Rhytisma spp.: In silver and red leaves Each tar spot is a point of infection- Where a spore hit the growing leaf In a bad year, tar spot might defoliate the tree But the trees survive, make new leaves After spending winter on the ground, the spots split open and shoots spores just as new maple leaves are forming Ascospores are like needles A little raking can decrease the disease Fungicide sprays aren’t really needed Although homeowners get upset, we are not so worried about maples- Lots of tree diseases fall into this categoryo Sudden Oak Death:These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. Caused by phytophtoraramorum- Tree Diseases in General:o Every kind of tree is affected by many kinds of diseaseso Normally, tree diseases kill the weak and the strong surviveo Trees and their pathogen are engaged in a constant, slow evolutionary battle- Managing Plant Diseases:o In agriculture. We rely on: Breeding new resistant varieties of plants that can completely or partially resist pathogens Treating crops with fungicideso These strategies are hard to apply to forest trees- Global Trade and Diseaseo Our most devastating trees diseases are often introductions from elsewhereo When a foreign pathogen is introduced to a place where the trees haven’t met it before.. The rate of disease introductions is increasing:- Chestnut blight- Dutch Elm