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How to Manage Pests
UC Pest Management Guidelines
Carrot
Cercospora Leaf Blight
Pathogen: Cercospora carotae
(Reviewed 1/09,
updated 1/09)
In this Guideline:
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Cercospora blight can occur on any above ground carrot tissue.
However, symptoms are usually most severe and obvious along leaflet margins.
Infection sites initially appear as a brown spot with a dark brown margin. A
chlorotic halo often develops around these spots. As the disease progresses,
the leaflets become yellowed and curl at the margins. Lesions on leaf petioles,
stems, and flower parts are usually elongated and dark brown. Under heavy
disease pressure, severe loss of foliage may occur.
Cercospora blight is usually of minor importance in California but
often occurs in coastal carrot-growing regions. Cercospora carotae can be seedborne, but also survives between crops on
plant debris or in the soil. Infection occurs over a wide range of temperatures
with an optimum at 82°F.
Cultural Control
Use disease-free seed or treat seed with fungicides before planting.
Destroy diseased crop refuse by plowing it under to insure decomposition and
practice 2- to 3-year crop rotations.
Organically Acceptable Methods
Cultural controls are acceptable for use on organically grown produce.
Monitoring
and Treatment Decisions
In fields with a history of Cercospora leaf blight, start fungicide
applications when conditions are conducive to disease development or when
disease is observed.
| Common name |
Amount/Acre |
R.E.I.+ |
P.H.I.+ |
| (trade name) |
|
(hours) |
(days) |
|
| When
choosing a pesticide, consider information relating to environmental impact. Not all registered pesticides are listed. Always read label of product being used. |
| |
| AFTER PLANTING |
| A. |
AZOXYSTROBIN |
| |
(Quadris) |
9.2–15.5 fl oz |
4 |
0 |
| |
MODE
OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11) |
| |
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. |
CHLOROTHALONIL |
| |
(Bravo Weatherstik) |
1.5-2 pt |
12 |
7 |
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MODE
OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M5) |
| |
COMMENTS: Apply in sufficient water to
obtain good coverage. Repeat applications at 7- to 10-day intervals as needed
to maintain control. May be applied by sprinklers. Check the product label for specific application requirements. |
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| C. |
COPPER HYDROXIDE |
Label rates |
24 |
0 |
| |
MODE
OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M1) |
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COMMENTS: Repeat applications at 7- to 14-day intervals, depending on disease severity. |
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| D. |
PYRACLOSTROBIN |
| |
(Cabrio) EG |
8–12 oz |
12 |
0 |
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MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11) |
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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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| E. |
TRIFLOXYSTROBIN |
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(Flint) |
2–3 oz |
12 |
7 |
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MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11) |
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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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UC IPM Pest Management Guidelines: Carrot
UC ANR Publication 3438
Diseases
J. Nunez, UC Cooperative Extension, Kern County
R. M. Davis, Plant Pathology, UC Davis
T. A. Turini, UC Cooperative Extension, Fresno County
Acknowledgment for contributions to Diseases:
B. W. Falk, Plant Pathology, UC Davis
F. F. Laemmlen, UC Cooperative Extension, Santa Barbara County
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