clavipes) affects many plants in the rose family.Īdditional alternate hosts include common juniper, prostrate juniper, Rocky Mountain juniper, and savin juniper. Its telial phase is short and stubby, and its spots on apple or crabapple leaves are initially yellow and then turn orange.Ĭedar-quince rust ( G. These other fungal diseases have life cycles similar to that of cedar apple rust, but their telial phases are less dramatic.Ĭedar-hawthorn rust ( Gymnosporangium globosum) affects pear, serviceberry, and quince.Īdditional alternate hosts include Rocky Mountain juniper, common juniper, and prostrate juniper. Other Fungal RustsĪdditional rusts plague apples and crabapples in addition to other types of fruit. Unfortunately, you need to treat them repeatedly from mid-summer until fall, which can be expensive. You can treat them with a liquid copper product like you would with apple trees. The time to treat the junipers is before the galls produce their teliohorns, or when they are producing the aeciospores. This can also help to reduce the amount of cedar apple rust on your tree. Should You Treat Junipers?Īlthough the galls don’t do much damage to junipers, treating them with fungicide can help prevent their spores from spreading. You can find this product in most farm and home stores ( such as Tractor Supply) or you can purchase it through ARBICO Organics. It contains myclobutanil as its active ingredient.Ĭopper is not a cure-all, but it can help in preventing damage to the leaves and fruit. Several extension agencies recommend that you use Immunox® to control cedar apple rust. Unfortunately, captan, the fungicide in many pre-mixed sprays for home fruit trees, does not work on this particular fungal pathogen. Only certain types of fungicides are effective.Įxtension agents at North Carolina State University attribute this trend to an increase in occurrences on apple trees in the state. The fungus that causes apple scab is now frequently resistant to the sterol-inhibiting fungicides, and manufacturers have moved on to using newer classes of fungicides. In the old days, sprays for apple scab would also take care of cedar apple rust. They are known as “SI,” or sterol inhibitors. The most effective types of fungicides to use are those that inhibit fungal sterols. The time to treat your tree is between the pink stage of the blossoms (when the leaves are turning green) to the period when the petals drop. This is critical in the spring, when the juniper galls are releasing their spores. If your tree has a history of infection with cedar apple rust, you will want to get ahead of the infection and take preemptive measures. Later in the summer, brownish cylindrical tubes with hairs sticking out appear underneath the yellow spots, or on the twigs and fruit. Instead of galls, infected apple and crabapple trees manifest circular yellow spots on the upper surface of their leaves soon after bloom. As few as 4-5 hours of rain at 50-75☏ is time enough to produce a severe infection on apples. If conditions are right, these telial horns produce another type of spore that produces yet another kind of spore, which is blown back to infect apple leaves and fruit. To make them even more outrageous, the telia are gelatinous. Instead of turning into a cockroach, the galls swell and grow spurs called telial horns that are brown at first but turn bright orange in the rain.Īpple cedar rust is straight out of the disco era with its large galls and radically orange telial horns that protrude in all directions. Not only do the galls on junipers look like an organism from a bad 1960s sci-fi movie, but the reproduction process is also something usually found only in a Star Trek episode.ĭuring the spring rains 18 months later comes a metamorphosis that rivals that of Kafka’s.
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