Spring is a busy time for most ag operators, and the citrus industry is no exception. According to the experts at UF/IFAS, Spring is the time when Florida citrus growers should map out their foliar disease management plans. The Florida Citrus Production Guide should be your go-to resource for disease management, including pesticide applications and precise timing.
Plan for These Citrus Foliar Diseases
Postbloom Fruit Drop: Thankfully, we are in a neutral El Niño Southern Oscillation phase, which lowers the risk of Postbloom Fruit Drop (PFD) due to average temperatures that are higher than normal and average rainfall that is lower than normal. The fungus that causes PFD likes moderately warm temperatures and wet weather because rain splash-disperses the spores. PFD could still be a problem if your grove experiences a lot of rain—at least 15 hours of continuous wetness—and moderately warm temperatures, especially if you have had problems with PFD in the past. Use the Citrus Advisory System – AgroClimate to keep track of PFD risk for your area.
Scouting is important, especially if you’ve experienced PFD in the grove in the past. Look for persistent calyxes (buttons) from the prior year and the peach to pinkish-brown PFD lesions on early blooms and, if present, treat the blooms once there are enough of them for the treatment to be economical.
Strobilurin-containing fungicides (FRAC MOA 11) like Abound, Amistar Top, Gem, Headline, Priaxor, and Pristine are effective, but they should not be used alone more than once per season due to being prone to resistance development. Ferbam (FRAC MOA 03) can be used with low rates of a strobilurin fungicide to allow for repeated applications of strobilurin-containing fungicides.
Greasy Spot: Or rind blotch, is most problematic for those using CUPS, IPCs, and conventional grapefruit. For oranges, use a timely application of 435 oil during the flush, usually late May to early June. For grapefruit, use fungicides such as copper (FRAC M 01), strobilurins, or demethylation inhibiting (DMIs) fungicides (FRAC 3).
Black Spot: Find updated Black Spot quarantines at https://www.aphis.usda.gov/plant-pests-diseases/citrus-diseases/citrus-black-spot; the disease is likely as weather conditions last year were so favorable for black spot.
Plan for fungicide applications like copper (works best when combined with oil), DMIs, and strobilurins starting in May and continuing through September or even October, depending on rainfall.
Citrus Canker: This can be suppressed with copper, a boon if you are utilizing copper for another disease, but it must be timely. Use the Florida Citrus Production Guide to best choose your treatment plan for citrus canker, as the timing is dependent on the variety you grow and fruit development.