How to Manage Pests
UC Pest Management Guidelines
Carrot
Powdery Mildew
Pathogen: Erysiphe polygoni
(Reviewed 10/05,
updated 10/05)
In this Guideline:
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Older leaves and leaf petioles of plants with powdery mildew are
usually covered with a white, powdery growth. Young leaves develop small,
circular, white, powdery spots that slowly enlarge to cover the leaflets. A
slight chlorosis or yellowing may appear on leaves infected by the fungus.
The fungus survives on overwintered carrots and related weed hosts.
The airborne spores may be carried great distances. Foliage symptoms usually
do not appear until leaves are mature, and leaves can survive even with
heavy
infections. Fungal infection and disease development are favored by high
humidity during evening and morning hours, and temperatures between 55° and
90°F.
Cultural Control
Use tolerant cultivars and maintain good plant vigor.
Organically Acceptable Methods
Cultural control and sprays of sulfur and Bacillus subtilis are acceptable for use on organically grown produce.
Treatment Decisions
Chemical controls are not recommended, unless infections appear very
early in the growing season.
| Common name |
Amount/Acre
|
P.H.I.+ |
| (trade name) |
|
(days) |
|
| A. |
AZOXYSTROBIN |
|
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| |
(Quadris) |
9.2–15.4 fl oz |
0 |
| |
MODE OF ACTION: A Qol (Group 11)1
fungicide.
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COMMENTS: Do not make more than one
application before rotating to a fungicide with a different mode of action.
Do not make more than four foliar applications of strobilurin fungicides per
crop.
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| B. |
PYRACLOSTROBIN |
|
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| |
(Cabrio) EG |
8–12 oz |
0 |
| |
MODE OF ACTION: A Qol (Group 11)1
fungicide.
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COMMENTS: Do not make more than two
sequential applications before rotating to a fungicide with a different mode
of action. Do not make more than three applications of strobilurin fungicides
per crop.
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| C. |
TRIFLOXYSTROBIN |
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(Flint) |
2–3 oz |
7 |
| |
MODE OF ACTION: A Qol (Group 11)1
fungicide.
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COMMENTS: To limit
potential for resistance development do not apply more than 3 sequential
applications or a total of 4 applications of all strobilurins per season. Do
not apply more than 12 oz/acre/year.
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| D. |
SULFUR# |
3-10 lb |
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...OR... |
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SULFUR DUST# |
Label directions |
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MODE OF ACTION: A multi-site contact
(Group M)1 inorganic fungicide.
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COMMENTS: Apply at first sign of
disease and repeat at 14 days as needed to maintain control.
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| E. |
BACILLUS SUBTILIS |
|
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(Serenade MAX)# |
1–3 lb |
0 |
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(Serenade ASO)# |
2–4 qt |
0 |
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MODE OF ACTION: Unknown. |
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COMMENTS: Serenade ASO has a special local needs registration
for organically grown carrots. Apply Serenade MAX as a foliar spray; thorough
coverage is essential. Serenade ASO is applied with chemigation equipment. |
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UC IPM Pest Management Guidelines: Carrot
UC ANR Publication 3438
Diseases
R. M. Davis, Plant
Pathology, UC Davis
F. F. Laemmlen, UC Cooperative Extension, Santa Barbara Co.
J. Nunez, UC Cooperative Extension, Kern Co.
T. A. Turini, UC Cooperative Extension, Imperial Co.
Acknowledgment for contributions to the diseases section:
B. W. Falk, Plant Pathology, UC Davis
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