Citrus trees are a common sight in and around central Florida. With the rise in orange juice prices, many homeowners are trying their hand at growing citrus trees at home. While our moderate winter weather is perfect for the development of citrus fruit, there are a few things homeowners should know about pests and diseases that may affect the quality of citrus. Planting new citrus trees in the right space is the key to healthy fruit. Citrus trees must have uniform soil moisture to produce the highest quality fruit, so it is important to plant trees in elevated areas where soil drainage is good. Proper soil pH is also important in reducing insect infestations and avoiding nutritional deficiencies. According to the University of Florida, IFAS Extension, the optimal soil pH for citrus fruit is 6.0 to 6.5. You may encounter some problems in your citrus trees once they have become established and are producing fruit. Splitting is one of the most common problems in citrus fruit. Certain cultivars such as Navel, Hamlin and Valencia split more often than tangerines, tangelos and grapefruit.
While the exact cause of fruit splitting is unknown, it is more common in the late summer when humidity is high and rain is frequent. In our area, this is usually from late August until the end of the fall. Citrus fruit splits when the water from rainfall causes the fruit to expand rapidly. Nutritional deficiencies such as low potassium can also cause citrus fruit to split. Yellow vein chlorosis is another common problem in central Florida citrus. This condition occurs when trees suffer damage or when root rot is present. If the soil is deficient in nitrogen, it can also cause yellow vein chlorosis to occur. When this disease strikes, the middle of leaves turn yellow and the border of the affected leaves remain green. During the summer months, citrus fruit can become sunburned, which can ruin the fruit. This occurs when the fruit is exposed to excessive sunshine and high heat for prolonged periods of time. Certain thin-skinned cultivars such as the Murcott tangerine are at an increased risk of developing sunburn. The most serious citrus diseases are caused by bacterial infections. Citrus canker is characterized by the distinctive lesions that appear on infected fruit. Early on, these lesions look like tiny blisters that turn into watery looking spots over time. These spots can eventually rot, leaving unsightly holes in the fruit. As citrus canker spreads, infected trees lose their leaves and suffer dieback. One of the biggest problems with citrus canker is that it spreads easily on the wind or in the rain. Even cutting the grass near infected trees can spread it to other citrus trees nearby. Some diseases live in the soil, where they remain dormant until citrus trees are planted. Phytophthora is a soil-borne disease that damages the tree's roots. Trees with this disease can develop yellow, chlorotic leaves, fruit drop, dieback and eventual death. Phytophthora also causes trees to exude a reddish-colored resin. This root rot disease is most common in trees planted in very wet soils with poor drainage. Citrus trees can be infested with a wide variety of insects. In central Florida, aphids, whiteflies, scales and mealybugs are the most common citrus pests. These insects feed on plant sap, then excrete a sticky substance known as honeydew resulting in the development of sooty mold. This condition is not only unsightly, but it can affect the quality and color of mature fruit. Mites such as the citrus rust mite can be found on all citrus cultivars in Florida. Mite populations are usually apparent in June or July and increase in late fall around October and November. Citrus rust mites can make fruit unsalable but they are usually controlled with oil applications if diagnosed early on. Learning to recognize the signs and symptoms associated with common Florida citrus pests and diseases is an important factor in growing healthy citrus. With a little time and patience, you can learn to grow your own citrus fruit right in your own backyard.