Devastation by fire blight (Erwinia amylovora) of a 2-year-old high-densityGala apple orchard in Michigan after a violent storm. Other orchardsin the path of the storm had similar losses.
Photograph courtesy Alan L. JonesDepartment of Botany and Plant PathologyMichigan State University, East Lansing 48824
Background: Truly damaging outbreaks of fire blight, caused by the bacterium Erwinia amylovora, are becoming increasingly common in Michigan’s high-value apple orchards. This year, it is orchardists in the west-central Michigan fruit belt who are experiencing devastating losses after a severe rainstorm on 31 May 1998 that had winds estimated up to 140 miles per hour. It was initially estimated that the storm had destroyed 60,000 trees and injured another 60,000 (The Great Lakes Fruit Growers News, 1998, Volume 27). Two weeks later, as predicted by a program for forecasting fire blight (MARYBLYT), fire blight symptoms began to show up on trees that had survived the storm. Then a hailstorm on 16 June further compounded the problem by spreading bacteria to fresh injuries. Young trees in high-density plantings are particularly vulnerable to infection. Cultivars exhibiting the greatest damage include Gingergold, Gala, and Jonathan. In early July, E. amylovora began to ooze from the rootstock of trees on Malling 9 and 26 rootstocks after the apparent movement of the pathogen through symptomless scion tissues into the rootstock. The presence of E. amylovora in the ooze was confirmed by isolation of the bacteria and identification by PCR. In August, many apparently healthy trees will exhibit discoloration of the foliage and then collapse and die as the pathogen girdles the tree.
APS publication number: IW00008
Picture your photograph as the APSnet Featured ImageClick here to find out more
License to Copy. This notice hereby grants permission to APSnet users to copy the image featured for noncommercial, personal use. All components of APSnet are copyrighted and may not be reproduced or distributed except by express permission of APS. Copyright is not claimed for material provided by United States government employees as part of their work. APSnet copyright extends to images, text, graphics, photographs, illustrations, audio, video, computer software, and all other elements of the site.Instructions to Copy. For PC, position your mouse cursor on the featured image, click the right mouse button, and choose "Save Picture As..." or "Save this Image as..." whichever is the case. For Mac, click the only mouse button and follow the same steps. Users may want to set up a specific directory and file naming scheme for storing images; otherwise, they will be saved using your system defaults. Images may be used in any software application that supports JPEG file format or viewed in an Internet browser as local files.