Some cultivars of ornamental Callery pears were developed and marketed, at least in part, with the idea of providing resistance to fire blight. That resistance has not always held up in the landscape. In past issues of this newsletter (no. 1, 2004; no. 3, 2003), you can find more information about fire blight. Recently, I have received a few calls and one positive sample of fire blight on ornamental pear, so this problem is again upon us. Read through past HYG news articles and refer to Report on Plant Disease, no. 801, “Fire Blight of Apple,” for details about the disease and its management. RPDs can be found on the Extension VISTA Web site, www.ag.uiuc.edu/%7Evista/pubs.html, or in local Extension offices. Look for water-soaked or wilted new growth that quickly turns brown to black and remains attached to the stem. Also, dark cankers may develop in the wood of Callery pears.
Infections occur through blossoms or wounds. It may be tempting to boost new growth with high fertilization rates, but overfertilization should be avoided. Succulent new growth is more susceptible to infection because it is easily wounded.