Hi,
We live in Etobicoke and have a 14 yr old cherry tree on our front lawn, approximately 24ft tall, 16ft wide. Our lawn faces south and the tree gets full sun and has good drainage. It flowered beautifully this spring and produced a huge crop of cherries. In the last couple of weeks the leaves have been rapidly turning yellow, speckled and falling dead to the ground. Is this Cherry Tree Leaf Spot? How can we treat this?
Many thanks.
Thank you for contacting Toronto Master Gardeners. We believe you have correctly identified the problem with your cherry tree, however, you may want to review these photos of cherry leaf spot (Blumeriella jaapii) to absolutely confirm the disease.
The Ontario fruit growers blog provides the following information on fungus symptoms and life cycle. Please visit the blog for detailed information, but here are a few points about this fungal disease:
Symptoms:
“Small purple lesions on the upper leaf surface can appear within 5 days if there are damp conditions and the temperature remains steady between 16 and 20°C. This incubation period could take as long as 15 days though if lower temperatures and drier conditions occur.
As spots accumulate on leaves, the leaves turn yellow and fall. The number of lesions required causing leaf yellowing and drop is variable. Sweet cherries can tolerate quite a few lesions before leaf drop occurs; however, Montmorency tart cherries will drop with only a few lesions, signifying the importance of proper leaf spot management. Less than 50 percent defoliation by early September is considered acceptable control in Michigan.”
Life Cycle
“This disease is caused by a fungus that overwinters on fallen leaves on the orchard floor and produces spores in the spring. The primary infection period may last two to six weeks depending on conditions. Ascospores develop between 6 and 16°C with ascospore discharge increasing with temperatures between 8 to 30°C. A wet period of only a few hours is enough for spore germination. Development of visible lesions occurs in 5 to 15 days. Temperatures of 16-20ºC are most favourable for disease development.”
We are glad to hear that your tree flowered well and produced a good crop. However, if the leaves are infected early and drop prior to cherry harvest, the cherries may not mature properly. Has cherry leaf spot been an issue with this tree in past years? Repeated serious infections can lead to winter injury as mentioned in the above link.
Ensure your tree is healthy by monitoring moisture levels, fertilizing as needed and practicing good sanitation by raking up fallen leaves and other plant debris (do not compost, put in the garbage) to reduce the number of spores. If the centre of the tree is dense, consider pruning in late winter when the tree is dormant in order to open up the interior and allow better airflow and sun exposure.
If your tree has had severe symptoms over several years (most or all of the leaves turning yellow and dropping early), fungicides may help to control cherry leaf spot in the future. Please be aware that fungicide applications are preventative and will not “cure” current symptoms. Applying fungicides earlier – at bract leaf stage rather than full leaf stage – has been suggested as a more effective control before fruit harvest and may help leaves from early drop.
Ontario’s Cosmetic Pesticide Ban prohibits the use of many pesticides (including fungicides) for cosmetic use by homeowners. Visit a reliable garden centre or nursery to see what fungicides are available for home use. Carefully read the label for accepted uses, frequency and potency.
You may want to consult with an ISA certified arborist regarding pruning and correct fungicide applications. They will be able to provide you with the right treatment to keep your tree healthy.
Good luck with your tree!