It was most dismaying to return to school in August, looking forward to a new cider season, only to find the leaves and fruit in our orchard covered with bright orange and black spots. A mild and rainy spring had caused our trees to become infected with the fungus cedar apple rust. Now our apples are small and pithy. We’ll have a lot less cider this year unless we can find another source for apples. Woodmont Orchard across the street, which has most kindly helped us out in the past, has fewer apples to spare this year. After a bumper crop in 2013, the harvest is likely to be a bust this year.
Cedar apple rust has an interesting life cycle. It requires both apples (or other rose-related species) and cedars (or other juniper-related species) in order to propagate. This spring, spores produced on junipers, wild or cultivated, landed on our apple leaves and blossoms just as they were emerging and were able to grow because the temperature was between 45 and 75° and were damp with rain. Orange spots formed as the mycelia that forms the body of the fungus invaded the plant cells. Damaged leaves means fewer nutrients for the tree and less healthy fruit for us. A couple months later spores were produced by those spots. Carried by the wind some of those millions will land on cedars planted in neighboring yards or on low-lying junipers down in Spalding Town Forest. There over the next year they will form a gall. Then, during the next spring rains, strange orange tentacle-like protrusions will emerge from the gall. Within a few hours these will begin to produce spores that the fungus forcibly propels into the air. And these float away, some perhaps to land and grow again on our trees.
Prevention is difficult. Removing all local cedars and junipers is challenging. Some apple cultivars are resistant. Spraying with a sulphur will reduce or even eliminate the infection, as will powerful fungicides. Sulphur is considered an organic solution. The rust does not kill the trees. Some simply hope that conditions are not, as they were this year, perfect for spore germination. As a back-up, we are considering working with a local farmer who might be able to spray our trees with sulphur when conditions warrant (and the children are away).