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.