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How to Manage Pests
UC Pest Management Guidelines
Sugarbeet
Rhizomania
Pathogen: Beet necrotic yellow vein virus (BNYVV)
(Reviewed 11/05,
updated 11/05)
In this Guideline:
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Rhizomania is characterized by root stunting and a proliferation of
lateral rootlets on the main taproot that give the root a bearded appearance.
The storage root is often constricted (turnip-shaped) below the soil level and
rotted. The vascular tissue of
the taproot becomes discolored and appears as darkened rings when the taproot
is cross-sectioned. Leaves on
the plant wilt, especially in periods of high water demand or following
irrigation when the fungal vector of the disease is most active. At the
beginning of summer, some leaves on plants may crinkle and bleach along veins,
but these symptoms can disappear after a few weeks.
Rhizomania is one of the most destructive diseases of sugarbeet. The
causal agent, beet necrotic yellow vein virus, is transmitted by the soilborne
fungus Polymyxa betae. Disease
development is influenced by the fungus, which is enhanced by saturated soil
conditions from rain, irrigation, or poor soil drainage. In infested fields,
most sugarbeets are affected: roots are usually small, sugar yields are poor,
and losses can be as high as 100%. Recent studies suggest that additional
losses in fields with infected beets may be the result of secondary invasion by
other root pathogens, such as Phytophthora or Pythium.
It is assumed that all commercial sugarbeet fields in California now
have rhizomania. Only plant rhizomania-resistant varieties. Current resistant
varieties are very high yielding and have provided protection over the last
decade. A resistance-breaking pathotype was observed in the Imperial Valley in
2003 and is slowly spreading. It may appear in the San Joaquin Valley in the
future. Avoid planting sugarbeets 2 years in a row in the same field, and avoid
fields known to contain the new strain until effective new resistant varieties
are developed.
UC IPM Pest Management Guidelines: Sugarbeet
UC ANR Publication 3469
Diseases
S. Kaffka, Agronomy and Range Science, UC Davis
R. T. Lewellen, USDA, Salinas
C. A. Frate, UC Cooperative Extension, Tulare Co.
T. A. Turini, UC Cooperative Extension, Imperial Co.
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