IFAS Extension
Application Timing Recommendations
- Thorough coverage of the undersides of leaves is important for greasy spot management.
- Higher spray volumes and slower application speeds will improve coverage for this disease.
- Two applications for fresh and processing fruit should be made.
- First in mid-May to June.
- Second early to mid-July.
- For fresh fruit, a third application in August may be needed if rind blotch was severe the previous year.
- Copper is an effective product but can cause phytotoxicity in the summer.
- Do not apply when >94°F or with oil.
- Use a spray volume of at least 125 gal/acre.
- Monitor residue levels with the Citrus Copper Application Scheduler.
Fungicide Resistance
Recently, isolates of the fungus responsible for greasy spot, Zasmidium citri-griseum, were identified as resistant to strobilurin (FRAC MOA 11) fungicides. Work on how common the problem is and how it relates to the fungicide use history of groves is ongoing. It is advised not to use strobilurin fungicides frequently, and it is best to use them in a premixture with an additional mode of action. If control failure is observed after strobilurin use, discontinue use.
Web Addresses for Links
Citrus Copper Application Scheduler: http://agroclimate.org/tools/citrus-copper-application-scheduler/
UF/IFAS publication PP289, "A Web-Based Tool for Timing Copper Applications in Florida Citrus": https://doi.org/10.32473/edis-pp289-2012
Recommended Chemical Controls
READ THE LABEL.
See Table 1.
Rates for pesticides are given as the maximum amount required to treat mature citrus trees unless otherwise noted. To treat smaller trees with commercial application equipment including handguns, mix the per-acre rate for mature trees in 250 gal of water. Calibrate and arrange nozzles to deliver thorough distribution, and treat as many acres as this volume of spray allows.
Table 1. Recommended chemical controls for greasy spot.
|
Pesticide |
FRAC MOA1 |
Mature Trees Rate/Acre2 |
|---|---|---|
|
Petroleum oil 97+% (FC 435-66, FC 455-88, or 470 oil) |
NC3 |
5–10 gal. Do not apply when temperatures exceed 94°F. 470 weight oil has not been evaluated for effects on fruit coloring or ripening. These oils are more likely to be phytotoxic than lighter oils. |
|
Copper fungicide |
M 01 |
Use label rate. |
|
Copper fungicide + Petroleum oil 97+% (FC 435-66, FC 455-88, or 470 oil) |
M 01 + NC |
Use label rate + 5 gal. Do not apply when temperatures exceed 94°F. 470 weight oil has not been evaluated for effects on fruit coloring or ripening. These oils are more likely to be phytotoxic than lighter oils. |
|
Amistar Top4,5 |
11 + 3 |
10–15.4 fl oz. Do not apply more than 61.5 fl oz (0.2 lb azoxystrobin and 0.13 lb difenoconazole)/acre/season for all uses. Do not apply more than 0.5 lb a.i./acre/season of difenoconazole. Do not apply more than 1.5 lb a.i./acre/season of azoxystrobin or 3 applications at the highest rate. For best results, use with a spreading/penetrating surfactant. Minimum retreatment interval is 7 days. |
|
Enable 2F5 |
3 |
8 fl oz. Do not apply more than 3 times per year; no more than 24 fl oz (0.38 lb a.i.)/acre. Minimum retreatment interval is 21 days. Do not apply with polymer-based spray adjuvants. |
|
Gem 500 SC4 |
11 |
1.9–3.8 fl oz. Do not apply more than 15.2 fl oz/acre/season for all uses. Best applied with petroleum oil. Do not apply within 7 days of harvest. |
|
Headline SC4 |
11 |
9–12 fl oz. Do not apply more than 54 fl oz (0.88 lb a.i.)/acre/season for all uses. Best applied with petroleum oil. |
|
Pristine4,5 |
11 + 7 |
16–18.5 oz. Do not apply more than 74 oz/acre/season for all uses. Do not apply more than 1.17 lb a.i./acre/season of boscalid. Do not apply more than 0.592 lb a.i./acre/season of pyraclostrobin as Pristine. Minimum retreatment interval is 10 days. |
|
Quadris4 |
11 |
12.0–15.5 fl oz. Do not apply more than 90 fl oz (1.5 lb a.i.)/acre/season for all uses. Best applied with petroleum oil. Minimum retreatment interval is 7 days. |
|
1 Mode of action class for citrus pesticides from the Fungicide Resistance Action Committee (FRAC) 2025. Refer to chapter 4, "Pesticide Resistance and Resistance Management", for more details. 2 Lower rates can be used on smaller trees. Do not use less than the minimum label rate. 3 No resistance potential exists for these products. 4 Do not use more than 4 applications of strobilurin-containing fungicides (FRAC MOA 11)/season. Do not make more than 2 sequential applications of strobilurin-containing fungicides. 5 Do not make more than 4 applications of Pristine or Amistar Top/season. Do not make more than 2 sequential applications of Pristine or Amistar Top before alternating to a non-strobilurin, non-SDHI, non-DMI fungicide. | ||
