Erysiphe syringae

Powdery mildew of lilac, or Erysiphe syringae (formerly Microsphaera syringae) is a fungal pathogen of lilacs.

Erysiphe syringae
Image of chasmothecia and mycelial growth through the lens of a dissecting scope
Scientific classification
Kingdom: Fungi
Division: Ascomycota
Class: Leotiomycetes
Order: Erysiphales
Family: Erysiphaceae
Genus: Erysiphe
Species:
E. syringae
Binomial name
Erysiphe syringae
Synonyms[2][3]
  • Microsphaera syringae (Schwein.) H.Magn. 1898

Importance

The host of the fungal pathogen, Syringa vulgaris or the common lilac, is an ancient plant with significance in horticultural activities and wild roots in eastern Europe.[4] Its Latin epithet, vulgaris, translates into ‘common’ in English, and was popularized by the pioneer taxonomist Carl von Linné. [5]

One of the first dutiful observations of the pathogen, E. syringae, was made in a journal of the German Botanical Society, Berichte der Deutschen Botanische Gesellschaft,[6] where it was observed as a powdery mildew pathogen unique to lilacs referencing the physical characteristics of its ascocarp appendages. [6]

The pathogen contributes to a deathly and diseased look. Common lilac is known for its spring flowers, which can be altered due to decay of flowering stems after intense infection.

Symptoms

Powdery mildew of lilac leaves an opaque-white discoloration on the leaves of S. vulgaris. This process is predominant at the end of the season but can begin to take place during new growth.[7] Eventually the fungal pathogen contributes to the damaging and early senescing of the infected leaves. The opaque-white discoloration is mycelial growth along the surface of the leaf. When the pathogen is sufficiently advanced, the presence of small dark dots indicates the production of cleistothecium (chasmothecium), an important structure in the protection of potential inoculum.[8]

Treatment

There are methods to treat powdery mildew using home-made preparations including fresh milk, which contains the active anti-pathogenic compound lecithin. [9] Lecithin is recognized by the European Union as a treatment for powdery mildews diseases and is commonly available in the soy-derived formulation ‘soy lecithin’. [10] Other experimental treatments include using baking soda (disrupts pH), neem oil (fungicidal properties), or sulfur containing solutions.[11] Historically, flowers of sulfur has been prepared into a dust and applied to the leaves. [7]

Synthetic compounds such as thiophanate-methyl,[12] propiconazole,[13] and chlorothalonil [14] are used to treat variety of powdery mildew diseases, as well as other fungal pathogens.

Many chemical treatments are known to contribute to disease resistance, and can be harmful if not used with appropriate caution. Compounds with high risk such as thiophanate-methyl can be referred to in the FRAC (Fungicide Resistance Action Committee) Code List document.[15] To avoid health risks refer to the product's label and the appropriate Material Safety Data Sheet.

Cultural controls such as selective pruning can prevent suitable environmental conditions of the pathogen by increasing air circulation. Collection and destruction of plant debris can disrupt the pathogen’s life cycle.

References
  1. Lewis David de Schweinitz, Transactions of the American Philosophical Society 4 (2): 270 (1832)
  2. "Erysiphe syringae". Mycobank. Retrieved 29 December 2019.
  3. "Microsphaera syringae". Index Fungorum. Retrieved 29 December 2019.
  4. Alexander III, John H. (1990). "Lilacs of the Arnorld Arboretum". The Arnorld Arboretum of Harvard University. Archived from the original on 2019-10-01.
  5. Linné, Carl von (2007-03-08). Species Plantarum, Sections I-III (in Latin). Archived from the original on 2019-12-11. Retrieved 2019-12-11.
  6. Deutsche Botanische Gesellschaft.; Gesellschaft, Deutsche Botanische (1898). Berichte der Deutschen Botanischen Gesellschaft. v. 16 (1898). Berlin: Gebrüder Borntræger. Archived from the original on 2019-12-11. Retrieved 2019-12-11.
  7. Weiss, Freeman.; Weiss, Freeman. Powdery mildew of ornamental plants /. no.197. Washington, D.C.: U.S. Dept. of Agriculture. Archived from the original on 2019-12-11. Retrieved 2019-12-11.
  8. Agrios, George N., 1936- (2005). Plant pathology (5th ed.). Amsterdam: Elsevier Academic Press. pp. 470–480. ISBN 0-12-044565-4. OCLC 55488155.CS1 maint: multiple names: authors list (link)
  9. NDR. "Mehltau vorbeugen und natürlich bekämpfen". www.ndr.de (in German). Archived from the original on 2019-07-26. Retrieved 2019-12-11.
  10. "European Commission Directorate-General For Health and Food Safety".
  11. Newman, S. (1999). "Fact Sheet No. 2902, Gardening Series: Diseases" (PDF).
  12. "Thiophanate-Methyl (cas 23564-05-8) msds download - Guidechem.com". www.guidechem.com. Retrieved 2020-01-14.
  13. "propiconazole (cas 60207-90-1) msds download - Guidechem.com". www.guidechem.com. Retrieved 2020-01-14.
  14. "chlorothalonil (cas 1897-45-6) msds download - Guidechem.com". www.guidechem.com. Retrieved 2020-01-14.
  15. "Fungal control agents sorted by cross resistance pattern and mode of action (including FRAC Code numbering)" (PDF). Fungicide Resistance Action Committee. 2019. p. 3. Retrieved January 14, 2020.
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