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Plantwise Technical Factsheet

sugarbeet powdery mildew (Erysiphe betae)

Host plants / species affected
Amaranthus (amaranth)
Beta atriplicifolia
Beta corolliflora
Beta intermedia
Beta lomatogona
Beta macrocarpa
Beta macrorhiza
Beta patellaris
Beta trigyna
Beta vulgaris subsp. maritima (sea beet (UK))
Beta vulgaris var. cicla
Beta vulgaris var. saccharifera (sugarbeet)
Chenopodium (Goosefoot)
Cuminum cyminum (cumin)
Daucus carota (carrot)
Rheum palmatum
List of symptoms/signs
Leaves  -  abnormal colours
Leaves  -  fungal growth
Leaves  -  yellowed or dead
On leaves, circular, white, dust-like colonies of radiating hyphae develop and produce abundant conidia. Attack usually begins on the older leaves, sometimes initially in the angle made by the lower part of the leaf lamina joining the petiole. With heavier infection, the colonies coalesce and the entire leaf lamina becomes covered with mycelium, but the young leaves in the heart are rarely affected. Fungal mycelium can be seen on both the abaxial and adaxial leaf surfaces. Chlorosis is apparent and badly affected leaves senesce early. In some areas, infection may progress to form cleistothecia, but this is a rare event in some countries.

Inflorescences may become heavily infected with powdery mildew, particularly if the plant has been enclosed in a pollen-proof bag, as may occur in a breeding programme.

Seedlings at the cotyledon stage are rarely infected, except under conditions of physiological stress induced by severe overcrowding under glasshouse conditions.
Prevention and control
Chemical Control

Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources:

Cultural Control

Owing to the ubiquitous nature of E. betae conidia, often derived from wild Beta vulgaris subsp. maritima, and long-distance dispersal, any cultural control methods would probably have little effect on the prevalance of E. betae.

Infection of sugarbeet by E. betae is extremely damaging and results in both lower root yields and sugar contents. Heavy infections can reduce sugar yield by up to 30% in dry areas such as the Middle East (Weltzien and Ahrens, 1977) and an epiphytotic in the USA in 1975 reduced sugar yield by 27% (Hills et al., 1975). Disease development is faster when the sugarbeet plants are well supplied with water, but leaf death occurs more quickly if the plants are water stressed (Duffus and Ruppel, 1993). Generally, powdery mildew has been increasing in importance in beet-growing countries, but up until recently was thought to be not economically important in the Netherlands (Byford, 1996).
Related treatment support
Plantwise Factsheets for Farmers
Londase, V.; CABI, 2013, English language
Escobal Valencia, F.; CABI, 2018, Spanish language
Pest Management Decision Guides
CABI; CABI, 2018, English language
Raja; Rajeswari; Girija, D. S.; CABI, 2015, English language
Ndungu, J.; Njoroge, C.; Otipa, M.; CABI, 2015, English language
External factsheets
University of California IPM Pest Management Guidelines, University of California, 2010, English language
DPI NSW factsheets, New South Wales Government, Department of Primary Industries, Australia, 2003, English language
University of California IPM Pest Management Guidelines, University of California, 2009, English language
UF/IFAS Factsheets, University of Florida, 2002, English language
University of Illinois Extension Factsheets, University of Illinois, 1987, English language
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