Question from resident: Please help me save my citrus tree. It is about 5 years old from a local garden center. Had great and plentiful fruit two years ago. This year, six tangerines but they look pitiful. Any help would be most appreciated.
— Increase air circulation around the tree. To do this, make sure there’s no mulch at the base of the tree. You could pull mulch back from the base of the trunk and around the dripline. Citrus is an exception to mulching, as mulch can contribute to disease and phytophthora, which is a soil-borne fungus. Please see this link, especially where it mentions ants, and check for ants at the base of the trunk: https://edis.ifas.ufl.edu/pdf/HS/HS26100.pdf
— Prune out dead branches and discard in the trash and not in a compost pile or the landscape. This can take time but it will help the tree.
— Fertilize trees with a citrus fertilizer based on the age of the tree. For example, for a 5+ year old tree, UF/IFAS recommends fertilizing three times per year. This publication – Table 2 https://edis.ifas.ufl.edu/pdf/HS/HS13200.pdf – is a guide for how much to fertilize with common fertilizer formulations. Check this guide with how often you’re fertilizing and how much.
— Many times, homeowners aren’t fertilizing enough with regard to the amount of fertilizer in pounds per application. For example, if using a 6-6-6, you would apply 6.1 – 7.8 pounds of fertilizer three times per year.
— Fertilizer applications are important now that we have citrus greening disease: https://crec.ifas.ufl.edu/extension/greening/symptoms.shtml. This disease limits nutrient transport through the tree so supplemental fertilizing is helpful. Yellow and green blotchy colors on the leaf are indicative of citrus greening disease. Fertilizer can help but all citrus in FL are susceptible to the disease. Trees can be managed to some extent with fertilizer, irrigation, care and citrus foliar sprays until we get less susceptible varieties on the market.
— Check for pests such as leafminer and scale. See this publication on citrus leafminer, which can be difficult to control. https://trec.ifas.ufl.edu/mannion/pdfs/CitrusLeafminer.pdf
— Reducing plant stress might reduce pests. You could use a horticultural oil – available at garden centers – to coat the underside of leaves and the scale. Be sure to read the label because it usually cautions about not spraying oils when temperatures exceed 85 – 90 degrees F. Doing so can damage leaves in the heat. You could spray early in the morning or later in the evening when temperatures are cooler.
— Lastly, water the tree as needed if there isn’t an irrigation system. Watering once or twice a week if we have no rainfall may be helpful.