Powdery mildew of lilac, or ''Erysiphe syringae'' (formerly ''Microsphaera syringae'') is a fungal pathogen of
lilac
''Syringa'' is a genus of 12 currently recognized species of flowering plant, flowering woody plants in the olive family or Oleaceae called lilacs. These lilacs are native to woodland and scrub from southeastern Europe to eastern Asia, and wid ...
s.
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. Its Latin epithet, vulgaris, translates into ‘common’ in English, and was popularized by the pioneer taxonomist
Carl von Linné.
One of the first dutiful observations of the pathogen, ''E. syringae'', was made in a journal of the
German Botanical Society The German Society for Plant Sciences (also known as German Botanical Society, ''Deutsche Botanische Gesellschaft'', DBG) is a non-profit network for plant sciences and botany in the German-speaking area. It was founded 1882 at Eisenach, Germany. In ...
,
Berichte der Deutschen Botanische Gesellschaft,
where it was observed as a powdery mildew pathogen unique to lilacs referencing the physical characteristics of its
ascocarp
An ascocarp, or ascoma (), is the fruiting body ( sporocarp) of an ascomycete phylum fungus. It consists of very tightly interwoven hyphae and millions of embedded asci, each of which typically contains four to eight ascospores. Ascocarps are m ...
appendages.
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.
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.
Treatment
There are methods to treat powdery mildew using home-made preparations including fresh milk, which contains the active anti-pathogenic compound
lecithin
Lecithin (, from the Greek ''lekithos'' "yolk") is a generic term to designate any group of yellow-brownish fatty substances occurring in animal and plant tissues which are amphiphilic – they attract both water and fatty substances (and so ar ...
. 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’. Other experimental treatments include using baking soda (disrupts pH), neem oil (fungicidal properties), or sulfur containing solutions. Historically,
flowers of sulfur has been prepared into a dust and applied to the leaves.
Synthetic compounds such as
thiophanate-methyl,
propiconazole, and
chlorothalonil 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 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
{{taxonbar, from=Q10488583
syringae
Fungal plant pathogens and diseases