Cedar-Quince Rust

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Many ornamental fruit trees are showing signs of Cedar-Quince Rust this year due to the very wet conditions that we have experienced. Cedar-Quince Rust, Cedar-Apple Rust and Cedar-Hawthorn Rust are three very similar tree diseases that require two hosts to complete their life cycle. Along with the trees mentioned, the presence of a cedar tree is also required as the disease goes back and forth between the two plants. In the case of Cedar-Quince Rust on crabapples, hawthorns and quince or a few other ornamental fruit trees, the signs of the disease are the orange to pink aecia or tubes that cover the fruit and can develop on the branches of the tree. If the aecia develop on branches, they can form a canker that can lead to branch tip dieback. The spores from the aecia will spread to nearby cedars and junipers, where they will form perennial, elongated swellings on twigs and branches. The following year, these swellings will produce orange, gelatinous telia, which then produce spores that will re-infect the ornamental fruit trees. These swellings, or cankers, can continue to produce spores for 4 to 6 years. This is a cosmetic disease that doesn't usually damage a tree unless the aecia begin to develop on the branches and cause tip die-back. It is difficult to plan a tree care regimen to prevent this disease. Determining when to spray a fungicide requires knowing where the location of the cedar or juniper that is spreading the disease. Since the spores can travel up to two miles, the likelihood of knowing when to apply a preventive spray is very difficult. The time to spray is when the junipers or cedars have formed the gelatinous horns. The fruit will wither and fall off, which it will do anyway, so treating for Cedar-Quince Rust is usually not necessary.