![]() Insects also help spread the disease to healthy plants. In spring, the bacteria ooze out of the cankers and attract bees and other insects. The bacterium can survive the winter in sunken cankers on infected branches. Once established in the tree, fireblight quickly invades through the current season's growth into older growth.įireblight can be spread from diseased to healthy plants by rain, wind, and pruning tools. Initially the disease often enters the tree through natural openings, especially flowers and wounds in the spring. Dead leaves and fruit remain on the branches. Branches may be bent, resembling what is commonly referred to as a “shepherd's crook” (Figure 1). Young twigs and branches die from the terminal end and appear burned or deep rust colored. The bark at the base of blighted twigs becomes water soaked, then dark, sunken, and dry cracks may develop at the edge of the sunken area. Shephard's crook, a typical symptom of fireblight. The plants affected include Amelanchier (serviceberry), Chaenomeles (flowering quince), Cotoneaster (cotoneaster), Crataegus (hawthorn), Eriobotrya (loquat), Malus (apple and crabapple), Photinia (photinia), Prunus (flowering almond, plum and cherry), Pyracantha (pyracantha), Pyrus (pear), Rosa (rose), and Spiraea (spirea).įigure 1. The disease affects plants in the Rosaceae family, which includes trees and shrubs in orchards, nurseries and landscape plantings. Here are some facts and methods to help you avoid and control the disease. Fire blight attacks blossoms, leaves, shoots, branches, fruits, and roots. Fireblight can be a problem in Georgia and is particularly prevalent in some counties. Mila Pearce, Former IPM Homeowner Specialistįireblight is a destructive, highly infectious, and widespread disease caused by the bacterium Erwinia amylovora. 590:89, 2002.Alfredo Martinez, Extension Plant Pathologist ![]() To our knowledge, this is the first report of a natural outbreak of fire blight on plum in Hungary and the presence of the pathogen may seriously influence local stone fruit production in the future. On the basis of the symptoms, colony morphology, biochemical tests, and 16S rDNA sequence homology, the pathogen was identified as E. amylovora isolates, including type strain AJ233410 with 99% similarity and 100% homology with sequences FN434113 and FN666575, where the complete genomes are known. HE610678) and showed 99 to 100% sequence homology with a number of E. The sequence was deposited in GenBank (Accession No. A recombinant plasmid (2A2.5) was sequenced by M13 forward and reverse primers. The PCR products were cloned into a pGEM T-Easy plasmid vector (Promega, Madison, WI) and were transformed into Escherichia coli DH5α cells. For molecular identification of the pathogen, the 16S rDNA region was amplified from isolate EA-PlumBo1 with a general bacterial primer pair (63f forward and 1389r reverse) (3). The bacterium was reisolated from lesions on inoculated shoots, fulfilling Koch's postulates. Five days after inoculation, dark brown-to-black lesions and shepherd's crook symptoms were observed only on inoculated shoots. Shoots were kept at 26☌ and 80 to 100% relative humidity. Controls were injected with sterile distilled water. Pathogenicity was tested by injecting five healthy young plum shoots from the same tree with a 10-μl bacterial suspension of 10 7 CFU/ml. Biochemical tests were also used for identification, and the results of API 20E and API 50 CH kits (Biomérieux, Marcy l'Etoile, France), demonstrated that the bacterium belongs to Enterobacteriaceae. Isolates were gram negative and induced a hypersensitive reaction in tobacco (Nicotiana tabacum L. After 48 h of incubation at 26☌, the medium contained pure cultures of a bacterium with white mucoid colonies, which is morphologically consistent with E. ![]() Shoots containing regions of dead and healthy tissue were surface sterilized with ethanol (50-mg sample homogenized with 500 μl of sterile water and 50 μl of the homogenate streaked to King's B agar medium). The first occurrence of fire blight on European plum was recorded in Germany in 2002 (4). Symptoms were the same as fire blight, symptoms reported from other hosts and locations. The naturally infected shoots showed typical symptoms of fire blight including terminal shoots with brown-to-black necrotic lesions and later, shepherd's crook deformation. 'd'Agen') in the city of Budaörs, near Budapest. During July 2011, a severe, unusual disease symptom was observed on young shoots on a 10-year old plum tree (Prunus domestica L.
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