Chestnut blight treatment7/24/2023 ![]() Note how the pathogen causes the collapse of stems along the outer surface of the stem. Canker caused by a highly virulent form of Cryphonectria parasitica on American chestnut. Hypovirulence is not a registered treatment and should not be applied in orchards planning to harvest chestnuts.only pruning dormant trees, removing active cankers). eliminating close American chestnuts, cultivar selection) and cultural practices (e.g. At this time, there is no registered treatment for chestnut blight, so growers must rely on preventative measures (e.g.Don’t bring in stock from areas where blight is found.Keep blight away by keeping American chestnut trees off the farm.Japanese chestnut is tolerant, but can carry the fungus.European chestnut and hybrids are susceptible.The fungus may not kill the Chinese trees, but if it reproduces on them then it can act to promote the fungal pathogen into new areas. When infected, it acts like a carrier of the disease. Chinese can be infected but is mostly tolerant.For orchard production, it is critical to understand the following: There is a lot of information regarding chestnut blight, though much of it is focused on forest grown American chestnut. As these blight “tolerant” trees get older, they get larger and the infections increase in size. These crosses (Chinese X American hybrids) are blight susceptible in the sense that they may not die from blight, but they will allow the pathogen to grow, colonize and sporulate all over the tree, spreading the chestnut blight fungus for many miles around the infected tree(s). ![]() ![]() These trees are probably not pure Chinese, but have originated from seed collected from a Chinese chestnut tree pollinized by an American chestnut tree. It is also important to understand that Chinese-like trees can become infected with blight. It is also important to note that interplanting of Chinese and European chestnuts also leads to a pollen-generated problem called internal kernel breakdown (IKB) where European X Japanese hybrid trees produce nuts with decaying kernels when pollinized by Chinese chestnut trees. Research in Michigan has demonstrated that European hybrid chestnuts produce 2 to 5 times more nuts and go into production much sooner than Chinese chestnuts however, Michigan growers are faced with the challenge of chestnut blight infections reducing orchard productivity. Michigan is one of the only states where growers routinely plant both Chinese and European hybrid chestnut species, sometimes side by side in commercial orchards. mollissima) due to the continued presence of the chestnut blight pathogen in eastern states. crenata) and, eastern growers plant the naturally chestnut blight-resistant Chinese species ( C. Generally, growers in western states (a chestnut blight-free environment) can plant chestnut blight–susceptible European chestnut ( C. This fungus reduced the great American chestnut forest of the Appalachian Mountains to a simple sucker sprout population that rarely produces any nuts. American chestnut is the most susceptible species to chestnut blight, a fungus that was introduced to North America in the early 1900s. Chestnut blightĬhestnut blight is probably the single most important pathogen affecting chestnut production in Michigan and the primary factor that dictates which chestnut species is planted in commercial orchards in North America. Refer the the current Michigan Chestnut Management Guide for more information on nutrient management, scouting, and registered pesticides.
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