Hello. My garden faces west in Bloor West Village. It has full sun. My cherry tree planted last year was thriving in the spring with lots of blossoms but now it looks to be in distress. the leaves are drying out and have a blotchy appearance. There are some small holes in them but I can’t see any insects. Can you suggest a possible course of action? Thanks
Based on symptoms you have identified, this is a fungal disease called Leaf Spot. Due to rainy cool weather we have been all too familiar with this season, fungal diseases are going to be aplenty. So perhaps this was not as noticeable in years past, this year it is more evident. Generally the disease if not too extensive is not so serious, but if your tree undergoes heavier infestations in several successive years, this can weaken your tree.
Please find below several site links and excerpts, which should provide you with necessary background, cultural practices and fungicide recommendations.
I have highlighted several key points on fungicide application. Also please read instructions on your fungicide label to note important details such as ; conditions to spray, formulation, frequency, etc.
Good luck with the problem.
Pesticide Risk Reduction Program Pest Management Centre Agriculture and Agri-Food Canada
Damage: Cherry leaf spot or shot-hole, reduces flowering and weakens the tree. Leaves develop small purple to brown spots, with definite borders, in early summer. In July, the centres of the infected spots frequently fall out, giving a shot-hole appearance. The leaves turn yellow and fall. Cherry leaf spot often defoliates the tree by midsummer. Repeated defoliation makes the tree more susceptible to winter injury and may eventually kill it.
Life Cycle: The fungus overwinters on fallen leaves. In spring following wet weather, spores form and are dispersed by wind to new leaves where they cause infection. The initial leaf infections form spots and more spores are produced in the spots. These spores are rain splashed to infect other leaves. Secondary spread and infection by spores continues repeatedly, whenever wet, warm weather occurs, until leaves fall in autumn.
Chemical Controls: Most fungicides applied to sweet cherry for brown rot control will control cherry leaf spot. Copper applied to sweet cherry for bacterial canker, helps to control leaf spot. Captan, ferbam propiconazole and sulpur are registered for control of leaf spot on sweet cherry.
Cultural Controls: Cultural controls include good pruning to allow for rapid drying of foliage and good spray penetration. There are no practical methods to reduce primary inoculum.
If trees have a history of leaf spot infection severe enough to result in significant leaf loss before September, fungicides can be used to protect leaves. Fungicide applications should be started two weeks after bloom, when leaves are completely unfolded and repeated at the interval specified on the fungicide label through the growing season, including one application after harvest. Fungicides with an active ingredient of myclobutanil or captan will protect leaves from infection with cherry leaf spot when applied properly. The leaf spot fungi may develop resistance to myclobutanil if this fungicide is applied too frequently. To avoid fungicide resistance, alternate between myclobutanil and captan when making repeated fungicide applications. Fungicides with an active ingredient of copper may provide some protection against leaf spot infection and some formulations acceptable for use in organic production are available. Fungicides work best if combined with sanitation.