Citrus trees are generally fairly low-maintenance plants that thrive in many climate zones. However, they can suffer from several plant diseases, insects that rob them of their vigor and unsuitable growing conditions such as poor drainage that can cause them to perish. Whether your citrus tree is a lemon, lime, orange or grapefruit, its chances of survival are increased if you catch any problem early and take proactive steps to remedy the situation before it develops into a more serious problem.
Improve the drainage where your citrus tree grows if you notice fruit dropping prematurely or dieback of the tree in general. When the soil does not drain well, a condition known as brown rot can occur in the tree’s roots--it can eventually kill a citrus tree. You might need to dig up your tree and transplant it to an area that has sandy loam soil or move your tree into a large container with loose potting soil that drains rapidly and does not leave your tree’s roots constantly wet.
Feed citrus trees that develop yellowing leaves with an iron supplement, such as chelated iron. Yellow vein chlorosis causes the veins and midribs of leaves to turn yellow, leaving the rest of the leaves their normal green color. In severe cases of this iron deficiency the entire leaf can become yellow. In general, apply the product around the tree’s drip line, as directed on the product label.
Treat trees that develop cracked or split fruit by ensuring that you water and fertilize them on a regular basis. Cracked or split fruit can occur with trees growing in areas that have high humidity and abundant rain in late summer through fall. If you live in such an area and the fruit on your citrus tree cracks or splits open before it is ripe, consider building a shelter of clear plastic or fiberglass roofing above your tree to prevent it from getting too much water, especially if heavy rains occur after a dry spell. Make sure that you give your tree enough potassium. Fertilizers designed for citrus contain the correct percentages of nutrients these plants need.
Control powdery mildew with a sulfur spray. This fungal disease appears as a fuzzy white to black coating on both the tops and undersides of the leaves. The leaves can turn yellow and later drop if you don’t treat mildew. When the tree loses many leaves, the fruit can become sunburned. It spreads quickly, so it’s important that you watch for this disease and treat it promptly as soon as you notice it.
Control the citrus scab disease by spraying your tree with copper oxychloride spray. You’ll know if your tree has this fungal disease if the fruit and leaves develop rough bumps. This product is a chemical, so be sure to use it with caution by following label instructions because it can cause human health problems if you ingest or inhale it.
Spray your citrus tree with liquid copper fungicide if it shows signs of the fungal diseases known as greasy spot and melanose. Greasy spot causes leaves to form brown or yellow blisters on their undersides, while melanose, which usually afflicts only grapefruit trees, manifests itself as scabs on the fruit rind. This type of fungicide is classified as organic, and the chances of it causing burns to your tree are minimal.