Fire blight crabapple tree9/8/2023 Cankers on a tree’s bark that look like discolored or wet patches, often with areas of dead or decayed sapwood around their edges.You can identify fire blight by several characteristics: We comply with the Federal Trade Commission 1998 Children’s Online Privacy Protection Act (COPPA).Image by Penn State Department of Plant Pathology & Environmental Microbiology Archives, Penn State University, įire blight is a destructive disease caused by a bacterium ( Erwinia amylovora) that thrives in the warm, humid, and rainy weather that coincides with the start of the growing season, and it is easily spread. The 4-H Name and Emblem have special protections from Congress, protected by code 18 USC 707. Reference to commercial products or trade names does not imply endorsement by MSU Extension or bias against those not mentioned. This information is for educational purposes only. Quentin Tyler, Director, MSU Extension, East Lansing, MI 48824. Issued in furtherance of MSU Extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Michigan State University Extension programs and materials are open to all without regard to race, color, national origin, gender, gender identity, religion, age, height, weight, disability, political beliefs, sexual orientation, marital status, family status or veteran status. MSU is an affirmative-action, equal-opportunity employer, committed to achieving excellence through a diverse workforce and inclusive culture that encourages all people to reach their full potential. When to prune out fire blight: To prune or not to prune.Cut the parent limb 6 to 12 inches below the closest fire blight-infected shoot (shown in red) during the growing season.įor more information, please see other articles on fire blight from Michigan State University Extension news: A pruning management strategy is essential in order to prevent further infection as the bacteria can overwinter in the cankers and provide inoculum for the next growing season. If the infection is on the trunk of a main limb, remove the infected bark and do not cover the area with any other material. If the tree is dormant, the cut only needs to be 4 inches below the joint of the infected shoot on the parent limb. To prune an infected limb during the growing season, cut 6 to 12 inches below the infected shoot on the parent branch (Photo 2). If pruning is done in the dormant season, there is no need to sterilize the pruners. If the infection is rapidly spreading and the tree is actively growing, sterilize the pruners in a ten percent bleach solution between each cut. In order to manage fire blight, trees or shrubs should be carefully pruned during a period of dry weather. Therefore timely identification and management of the disease can prevent spread to older growth and to other nearby susceptible plants. As the disease progresses, it can infect the older growth forming cankers where the bacteria can overwinter.Īlso, as shown in the fire blight lifecycle, fire blight bacteria can be spread by pollinators. Infected new shoots turn brown and bend into a distinctive shepherds hook. The infected shoots or flowers die within 1 to 2 weeks of infection and provide inoculum for new shoots to become infected. When the bacteria infect the branches, the cankers ooze a watery, tan, bacterial substance. This summer in Michigan, there have been numerous reports of hail in a number of recent severe storms during late June and throughout July. Two opportunities when fire blight can enter are during bloom and after a thunderstorm where hail or high winds injure leaves and branches. The prime conditions for inoculation are when temperatures are between 75 and 85 degrees Fahrenheit and it is rainy and humid.īacterial organisms enter plant tissue through natural openings or wounds. ) and less commonly hawthorns ( Crataegus spp.), juneberry ( Amelanchier), mountain ash ( Sorbus spp.) and Spiraea. It not only affects those in the genus Malus, but also other members in the family Roseaceae such as pears ( Pyrus spp.), firethorns ( Pyracantha spp. Growers of the popular ornamental tree should be familiar with the host range, environmental conditions conducive for disease spread, and management strategies.įire blight is caused by the bacteria, Erwinia amylovora (Photo 1). In the last few weeks, numerous cases of fire blight on crabapples in landscape plantings have been confirmed by Michigan State University Diagnostic Services. However, the ornamental crabapple is also in the susceptible genus, Malus. Fire blight is traditionally thought of as a disease that infects trees in commercial apple orchards.
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