Asian pear blight - Erwinia pyrifoliae
EEffective: April 22, 2016 - December 31, 2020
Resources:
Pest Tracker
CAPS Pest Datasheet
Screening Aids:
Taxonomic Position:
Enterobacteriales : Enterobacteriaceae
Pest Type:
Bacteria
Pest Code (NAPIS):
FBAAEFX
| No manual – See Host Matrix |
These Approved Methods are appropriate for:
2020, 2019, 2018, 2017
Pest is vectored by:
No known vector.
Survey
Approved Method(s):
| Method | Instructions | NAPIS Survey Method |
|---|---|---|
| Visual | Continues to be under review. |
3031 - General Visual Observation |
Signs:
No specific signs are present.
Symptoms:
In pear: "Black-to-brown stripes in the midribs of leaves, brown-to-black leaf spots and necrotic petioles were observed on Asian pear (Pyrus pyrifolia cv. Shingo). Symptoms spread to entire branches, and also affected blossoms and fruitlets. Large areas of trees were found with these necrotic symptoms and a major portion of trees in an orchard could be affected" (Rhim et al., 1999).
Symptoms on pear trees Korean orchards remotely resembled those of fire blight (Erwinia amylovora) (Kim et al., 1999). Symptoms caused by the Japanese strain of E. pyrifoliae in pear are similar to symptoms caused by Korean strains (Beer et al., 1996; Kim et al., 1999).
In strawberry: "Strawberry plants expressed an intense brown to black discoloration of their immature fruits, their fruit calyx, and the attached stems. There were no symptoms observed on the leaves. The discoloration was also observed inside the young fruits, including an intense shining of the fruit tissue. In several cases, the release of bacterial slime on the surface of the young fruits and their attached stems has been observed. Fruits did not develop at all or were in many cases heavily malformed. Crop losses of up to 40% were found" (Wenneker and Bergsma-Vlami, 2015).
In apple: Symptoms in experimentally inoculated apple cultivars were generally weak and included leaf wilting (Kim et al., 2001). Symptoms were not always observed in apple, and the extent of damage caused by E. pyrifoliae is unclear and may not be significant (Kim et al., 2001).
Symptoms on pear trees Korean orchards remotely resembled those of fire blight (Erwinia amylovora) (Kim et al., 1999). Symptoms caused by the Japanese strain of E. pyrifoliae in pear are similar to symptoms caused by Korean strains (Beer et al., 1996; Kim et al., 1999).
In strawberry: "Strawberry plants expressed an intense brown to black discoloration of their immature fruits, their fruit calyx, and the attached stems. There were no symptoms observed on the leaves. The discoloration was also observed inside the young fruits, including an intense shining of the fruit tissue. In several cases, the release of bacterial slime on the surface of the young fruits and their attached stems has been observed. Fruits did not develop at all or were in many cases heavily malformed. Crop losses of up to 40% were found" (Wenneker and Bergsma-Vlami, 2015).
In apple: Symptoms in experimentally inoculated apple cultivars were generally weak and included leaf wilting (Kim et al., 2001). Symptoms were not always observed in apple, and the extent of damage caused by E. pyrifoliae is unclear and may not be significant (Kim et al., 2001).
Key Diagnostics
Mistaken Identities:
Symptoms of E. pyrifoliae may be confused with other known bacterial pathogens of pear, including Erwinia amylovora, Pseudomonas syringae pv. syringae, which are both found in North America (Rhim et al., 1999). "Candidatus Phytoplasma pyri" may also cause similar symptoms in pear and is also present in the United States (Seem�ller and Schneider, 2004).
There are numerous other pathogens which infect strawberry and may be confused with E. pyrifoliae. For example, Xanthomonas fragariae, the causal agent of bacterial angular leaf spot in strawberry, is present in the United States (Wenneker and Bergsma-Vlami, 2015). Erwinia amylovora has also been found to infect strawberry in Europe (Wenneker and Bergsma-Vlami, 2015). Dozens of viruses are also known to infect strawberry in North America, including the predominant Strawberry necrotic shock virus (Tzanetakis and Martin, 2013). Unlike E. pyrifoliae, viruses typically exhibit symptoms in strawberry leaves (Tzanetakis and Martin, 2013).
There are numerous other pathogens which infect strawberry and may be confused with E. pyrifoliae. For example, Xanthomonas fragariae, the causal agent of bacterial angular leaf spot in strawberry, is present in the United States (Wenneker and Bergsma-Vlami, 2015). Erwinia amylovora has also been found to infect strawberry in Europe (Wenneker and Bergsma-Vlami, 2015). Dozens of viruses are also known to infect strawberry in North America, including the predominant Strawberry necrotic shock virus (Tzanetakis and Martin, 2013). Unlike E. pyrifoliae, viruses typically exhibit symptoms in strawberry leaves (Tzanetakis and Martin, 2013).
In Progress / Literature-based Diagnostics:
There are several published molecular diagnostic methods for E. pyrifoliae. Kim et al. (1999) originally identified the species using nucleotide sequencing of the16s rRNA genes, real time PCR assay, and biochemical and physiological tests. Kim et al., (2001) developed a PCR which can distinguish E. pyrifoliae from E. amylovora and also identify E. pyrifoliae in necrotic plant tissue. Wensing et al. (2012) described two methods for identifying Erwinia pyrifoliae, including Matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS). Additionally, novel PCR primers were designed for four Erwinia species, including Erwinia pyrifoliae. These PCR primers were used by Wenneker and Bergsma-Vlami (2015) to identify E. pyrifoliae in strawberry.