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Black Spot and Leaf Drop on Crabapple Tree

Wesley Asked

I spray my tree with daconil as early as I can but still get spots and leaves falling off as soon as the leave are full on the tree. By the last of July, the tree is practically bare. I try to get them off the ground as quick as I can but this occurs every year. If it is a spray, please try to be specific.

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The Gardener’s Answer

Hi, Wesley: Apple scab is a common fungal disease that affects members of the rose family including crabapple (Malus spp.). Once the fungus is present, it can be difficult to control especially in rainy, humid weather. It sounds like you have done a good job cleaning up the fallen debris from previous years. Unfortunately, if any fungus is left to over-winter, that is all it takes for spores to spread the following growing season. In addition to good sanitation and cultural practices, fungicide sprays can be helpful in severely infected trees. Fungicides will not cure the disease that is already present but if used correctly, it can be helpful in preventing further spread. Proper timing of fungicide spray is essential in terms of effectiveness. The first spray of the season should be at bud swell and then at10-14 day intervals as directed by product instructions. Daconil is labelled for use on crabapples. It may take a couple of years to get it under control but improving the health of your tree is the goal. Diseased trees are more susceptible to additional insect and disease issues. You may consider having a certified arborist come take a look and prune out diseased parts and open the canopy if necessary. The Bullitt County Cooperative Extension will be a valuable resource for you. You can reach the offices at 502-543-2257. The horticulture/agriculture agent will be able to give you specifics in terms of spray times in your area. The following link is a publication with specific information regarding apple scab and treatment options for Kentucky gardeners. I hope this is helpful.

Angie Oakley

Kentucky Living, Ask the Gardener

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