Apple green crinkle disease renders fruit unmarketable. The disease can be a serious problem for fresh fruit production in the United States and around the world.
Because we do not have a rapid assay for this disease, the only way to detect it is to inoculate a fruiting apple tree (the indicator) with a bud from the tree to be tested. We then observe the development of fruit symptoms on the indicator. This is a very costly and time consuming process. Since the disease may not appear each year, the test must run for at least three cropping years. This delays any decision about the disease status of the sample being tested.
Apple green crinkle disease can be elusive. It is believed that cool temperatures for a period of up to 6 weeks following bloom are required for disease symptoms to appear. These conditions are not met every year so the disease may remain undetected for several years.
This increases the risk of the disease being spread inadvertently if a tree is selected for propagation in a year in which the symptoms are not evident. All of the trees propagated will be at risk of developing the disease. Propagation is the main method this disease is spread.
Reliable detection of disease such as apple green crinkle disease is critical to keep U.S. orchards productive, but time is of the essence. Delays in the introduction of new apple varieties into the nursery and production industry must be kept to a minimum to keep U.S. producers competitive with the global marketplace.