Dear Bruce:

Fungicides are a protectant, not a cure, so it’s important to get the fungicide on the leaves when they are first emerging. The first application should be done when buds are expanding and the leaves start emerging. You will need to do additional applications depending on the product you purchase. Always read and follow label directions. For additional information about apple scab, see our web page about apple scab at http://www.mortonarb.org/component/content/article/193-insects-diseases/730-apple-scab.html

Hi, Tina,

You’re right to be concerned about using fungicide over the pond. We don’t know of a systemic that works well with apple scab, but you can place a tarp over the pond, then spray the tree. After the spray has dried, you can remove the tarp. You will need to spray the tree several times. If you use the same tarp over again, make sure the side of the tarp that received the spray previously is still on top.

There are now direct trunk injections that claim to control apple scab. They are done in the fall to control the disease for the next season. This would be ideal in your situation but their efficacy has yet to be proven.