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How to Manage Pests
UC Pest Management Guidelines
Citrus
Septoria Spot
Pathogen: Septoria citri
(Reviewed 9/08,
updated 9/08)
In this Guideline:
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Early symptoms of Septoria spot appear as small, light tan to
reddish brown
pits on fruit,
0.04 to 0.08 inch (1 to 2 mm) in diameter, which usually do not extend beyond
the oil-bearing tissue. Advanced lesions are blackish, sunken, extend into the
albedo (white spongy inner part of rind), and are up to 0.8 to 1.2 inch (20 to
30 mm) in diameter. Dark brown to black fruiting bodies often develop in
these lesions, which usually do not extend beyond the oil-bearing tissue. The
spots are much more conspicuous after the fruit has changed from green to
yellow or orange. Small spots may develop into large, brown blotches during
storage or long-distance transportation. Septoria citri may also cause
similar spotting on leaves or twigs that are weakened by frost or pests.
The Septoria fungus causes
spotting of Valencia oranges, late season navel oranges, and occasionally of
lemons and grapefruit. It occurs in the San Joaquin Valley and interior
districts of southern California during cool, moist weather.
Infections begin when Septoria conidia are transported throughout the tree by rainfall. The spores
germinate with additional moisture from rain or dews and commonly infect
cold-injured fruit tissue and mechanical injuries. The damage to the rind
lowers the grade of the fruit and results in culling.
Septoria spot may be confused with copper injury and other
abiotic and biotic agents.
Apply a preventive copper spray in late fall or early winter, just
before or after the first rain. In years with heavy rainfall, additional
applications may be necessary.
For California oranges (Navels and Valencias) shipped to Korea:
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Make the first spray between October 15 and November
30.
- Use
a minimum of 2.5 lb metallic zinc equivalent per acre and a minimum of 1.65 lb
metallic copper equivalent per acre. When using 1.65 lb copper equivalent use a
minimum of 2 lb hydrated lime, and when using 4 lb copper equivalent, use a
minimum of 4 lb hydrated lime.
- Apply
as a dilute application with a minimum of 400 gallons per acre.
- Higher
rates of zinc, copper, and lime may be used as local conditions warrant but do
not exceed manufacturer's label rates.
- Bordeaux
sprays also meet the preharvest requirements for exporting oranges to Korea.
Use a minimum of 3.3 lb metallic zinc, 1.65 lb metallic copper, and 20 lb
hydrated lime in no less than 400 gallons per acre. Mix in following order:
zinc, then copper, followed by lime.
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Cover the entire tree canopy, skirt sprays are not
acceptable.
| Common name |
Amount to Use |
R.E.I.+ |
P.H.I.+ |
| (trade name) |
|
(hours) |
(days) |
|
| When choosing a pesticide, consider the general
properties of the fungicide as well as information relating to
environmental impact. |
| |
| A. |
FIXED COPPER/ZINC SULFATE/HYDRATED LIME# |
see comments |
see comments |
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MODE OF ACTION GROUP NAME (FRAC NUMBER1): Multi-site contact (M1) |
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COMMENTS: Use rates under MANAGEMENT for oranges to be
exported to Korea. Not all copper compounds are approved for use in organic
production; be sure to check individual products. For tank mixes, observe all
directions for use on all labels, and employ the most restrictive limits and
precautions. Never exceed the maximum a.i. on any label when tank mixing
products that contain the same a.i. Use the restricted entry interval and
preharvest interval of the product with the most restrictive label of those used in the tank mix. |
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| B. |
ZINC SULFATE/COPPER SULFATE/HYDRATED LIME# |
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(3-2-6-100) |
10–25 gal/tree |
see comments |
see comments |
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MODE OF ACTION GROUP NAME (FRAC NUMBER1): Multi-site contact (M1) |
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COMMENTS: For use on grapefruit, oranges, and lemons. Apply in
100 gal water from Oct.–Dec. or just before or after first rain. In the
Central Valley increase the amount of hydrated lime to 20 lb for the control
of leafhoppers, if populations of this pest are high; if populations are low,
use the 6 lb rate. Hydrated lime helps prevent copper toxicity under certain
environmental conditions. Use rates under MANAGEMENT for oranges to be
exported to Korea. For information on making Bordeaux mixture, see UC IPM
Pest Note: Bordeaux
Mixture, ANR Publication 7481. Be sure to follow label directions as well. For tank mixes, observe all directions
for use on all labels, and employ the most restrictive limits and
precautions. Never exceed the maximum a.i. on any label when tank mixing
products that contain the same a.i. Not all copper compounds are approved for
use in organic production; be sure to check individual products. Use the
restricted entry interval and preharvest interval of the product with the
most restrictive label of those used in the tank mix. |
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UC IPM Pest Management Guidelines: Citrus
UC ANR Publication 3441
Diseases
J. E. Adaskaveg, Plant Pathology, UC Riverside
Acknowledgment for contributions to Diseases:
J. A. Menge, Plant Pathology, UC Riverside
H. D. Ohr, Plant Pathology, UC Riverside
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