For years the trees, shrubs and other plants in my forest garden have been incredibly healthy with no sign of disease on them. However this year pear rust (gymnosporangium sabinae) arrived and I only really became aware of it as a problem today when I noticed ugly galls protruding from the lower surfaces of certain leaves. These leaves have had bright orange spots for several weeks and had I been aware of the disease this would have been a warning sign. Pear rust is unusual in that it needs both pear trees and juniper bushes to complete its life cycle. This article has more details.
Before looking this up I had been round the garden and collected a small bag of all the affected leaves I could find. Fortunately the trees are all small and easy to reach! If I see the tell tale orange patches in future years I will take the affected leaves off immediately to save the trees the stress of playing host to this fungus.
Over recent years it has become my habit to reference the most relevant forest gardening principle(s) at the end of each blog post. And this principle highlights just how being a forest gardener is a never ending journey of ever increasing learning and deepening understanding of what is unfolding before us.
Forest garden principle: Polyculture learning is slow learning.
Dormant pruning does a lot for some diseases. It removes some of the host material that the pathogens overwinter in. It increases air circulation (which inhibits the proliferation of some diseases). Also, it concentrates resources into more vigorous growth that tends to be more resilient to disease.
I use the pruning method advocated by Ann Ralph in her book ‘grow a little fruit tree’ (https://www.amazon.co.uk/Grow-Little-Fruit-Tree-Ralph/dp/1612120547/ref=sr_1_1?dchild=1&keywords=grow+a+small+fruit+tree&qid=1633862757&s=books&sr=1-1) don’t know if this link will work! She uses summer pruning to discourage vigorous growth to keep the trees small and it works well to keep my trees within the available space. This is the only instance of any fungal disease in years. It apparently lives perennially on juniper; and whilst I don’t have any and am not aware of any wild juniper hereabouts there may be cultivars in the neighbours’ gardens. If so I guess the rust will inevitably come back. I will keep my eyes peeled next year for the first signs and get the leaves off immediately.
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Oh gads! I LOATH summer pruning. I use the pruning methods that I grew up with in the Santa Clara Valley (while the last scraps of orchards were still here). Summer pruning was developed to facilitate fruit production within minimal space. It is described as ‘less work’, but without comparison to conventional dormant pruning. (Dormant pruning is actually a bit less work, and is more compatible with the natural life cycle of the subject fruit trees). In the end, summer pruning accomplishes most of what winter pruning does, and contains fruit trees more effectively. It partially disrupts the life cycles of many of the pathogens that afflict fruit trees, and invigorates the trees to be more resilient. Of course, I would still recommend removing all of the foliar debris that falls from the trees during winter, since some diseases overwinter in it. (For example, foliar blight can be a problem in ornamental pears here, especially among the evergreen pears that do not defoliate completely during winter.) You might want to investigate any correlation with air circulation and the proliferation of the disease. Many diseases proliferate in congested vegetation, such as rust and mildew on roses. Summer pruning increases foliar density (or more correctly, the density of branching), which is how it increased fruit production. Such increased density may also promote the rust. If so, you may want to prune any other encroaching vegetation away from the trees to improve air circulation. I really do not know if it would help. Although it works for my roses, my old apple tree rusted even with convention winter pruning and plenty of open space around it.