I've never heard of aster yellows, but will go google it - Thank you very much!

Kassie: Agree with Scott that what you describe sounds like powdery mildew, and it may be that a summer oil spray will stop it, although my personal choice during the growing season would be a fungicide, such as sulphur. However, at this late stage of the season, especially in cooler areas of Colorado, the leaves have already performed their function and there is little to be gained by spraying them now. It would be better to give the trees a good treatment or two with full-weight dormant oil spray after all the leaves have fallen in November, repeating it again in early spring just before bud break. Prevention of these types of diseases is always better than an attempted cure, and you should be alert for any signs of trouble next season and take action promptly if they appear. It wouldn't hurt to rake up and throw out the infected leaves after they have fallen to eliminate a possible source of overwintering infection. If you have other cherry trees nearby, you certainly don't want the mildew to spread to them. Summer oil is a specially formulated very light weight oil for growing season use, and is different from the heavier dormant oils usually used for winter spraying. It goes by various names, such as "Eco-Oil" or "Sun-Oil". It may be difficult for you to find summer oil locally, although there are any number of sources that can be found for internet ordering, and most larger mailorder nurseries carry this or a similar product. Application of a regular dormant oil when the trees still have healthy, growing leaves can result in phytotoxicity and burning or death of the leaves. Dormant alternatives to oil sprays for stone fruits include lime-sulphur and copper, which may be more effective at breaking a powdery mildew cycle than oil sprays. Copper is my personal choice for dormant spraying of peaches and apricots, and occasionally cherries, although my cherries have rarely suffered from leaf mildews. Copper can also retard or prevent stone fruit diseases such as bacterial canker, which is a serious problem of older stone fruit trees. If you post again, you might want to describe your location a little more specifically, since there is quite a difference between lowland and mountain areas of Colorado. Don Yellman, Great Falls, VA

I think that's a virus or some sort of pathogen that causes the weird growth -I've seen similar in other plants. I would suggest emailing your info & the picture to IFAS... Here is a link that might be useful: Plant Pathology @ UF IFAS

No problem with overproduction here - I'm in 9b, and they are marginal here. So it will remain as a small potted specimen. Even if it sets heavily, it is just a small bush=) Thanks for the account of your experience Tomas. This is a new plant, so that could be the case. I got it last summer. It produced flowers last fall, with no fruit, and I thought it was probably because repotting had triggered an out of season bloom. But had hoped that this spring's flowering would set fruits. I'll keep watching it and see what happens. Even if there isn't fruit, the flowers are delicate and smell wonderful.