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How to Manage Pests
UC Pest Management Guidelines
Sugarbeet
Powdery Mildew
Pathogen: Erysiphe polygoni
(Reviewed 11/05,
updated 1/10)
In this Guideline:
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The first signs of powdery mildew are small, white powdery spots
that appear usually on the under surface of older leaves when sugarbeet plants
are 2 to 6 months old. Under suitable conditions, the fungus spreads rapidly
over the entire surface of the leaf, and eventually to all leaves on affected
plants. Older leaves may yellow and eventually become necrotic and die.
Powdery mildew is an annual problem on sugarbeet in California. The
fungus overwinters on sugarbeet and other Beta
species such as swiss chard, table beet and wild Beta species that grow throughout the winter. Ideal conditions for
disease development are warm, dry weather; optimum temperatures for growth of
the fungus are between 60° and 86°F (15° and 30°C). Very high daily
temperatures of 100°F (38°C) or higher tend to arrest disease development.
Following initial infection, the fungus grows over the surface of the leaf and
produces asexual spores (conidia), which give the leaf a powdery appearance.
The conidia are airborne and can be carried considerable distances to start new
infections. If the disease is not controlled, 20 to 35% loss in sugar yield can
occur.
Currently, varieties with moderate resistance are available. Use
these varieties in combination with chemical control measures. Apply a
fungicide before, if possible, or when the first small, white powdery spots
appear on the undersurface of leaves. Repeated applications are necessary at 3-
to 6-week intervals if the disease reappears. Good coverage of the beet leaf
surfaces is essential.
| Common name |
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R.E.I.+ |
P.H.I.+ |
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Amount/Acre |
(hours)
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(days)
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| The following materials are listed in order of usefulness in an IPM
Program. Also, consider information relating to environmental impact. Not all
registered pesticides are listed. Always read label of product being used.
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| A. |
SULFUR# |
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(Dust) |
30 lb |
24 |
0 |
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(Micronized wettable) |
10 lb |
24 |
0 |
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MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M2) |
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COMMENTS: Other types of sulfurs may be used. |
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| B. |
PYRACLOSTROBIN |
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(Headline) |
9–12 fl oz |
12 |
7 |
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MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11) |
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COMMENTS: Maximum use per year is 48 oz/acre, but do not
reapply. Alternate use with other mode of action fungicides to avoid the rapid development of resistance by the disease organism. |
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| C. |
AZOXYSTROBIN |
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(Quadris) |
9.2–15.4 fl oz |
4 |
0 |
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MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11) |
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UC IPM Pest Management Guidelines: Sugarbeet
UC ANR Publication 3469
Diseases
S. Kaffka, Agronomy
and Range Science, UC Davis
C. A. Frate, UC Cooperative Extension, Tulare Co.
T. A. Turini, UC Cooperative Extension, Imperial Co.
W.M. Wintermantel, USDA-ARS, Salinas
Acknowledgement for contributions to Diseases:
R. T. Lewellen, USDA, Salinas
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