By Amit Levy
Citrus leprosis is an exotic viral disease not currently present in Florida citrus, although the virus is present in non-citrus hosts. This disease was reported in citrus in Florida and Brazil in the early 1900s, where it caused great crop and tree losses, but was eliminated from Florida in the early 1960s. In recent years, the disease is spreading in South and Central America, already reaching Mexico.
Citrus leprosis causes lesions on leaves, branches and fruit, leading to early fruit drop, dead branches and ultimately lower yield. Depending on the citrus variety, yield losses of up to 100% have been reported. In Brazil, 24% of production costs are attributed to the control of leprosis.
The virus that causes the disease is transmitted by false spider mites that are present in Florida. The combination of the existence of the disease vectors in Florida, and the presence of the virus in close production areas and in non-citrus plants in Florida, makes it a potential threat for the state’s citrus industry.
If leprosis arrives in Florida citrus, it will be very important to detect the disease as early as possible, before it spreads. Therefore, growers should be aware of the leprosis disease symptoms, so they can recognize them early.
Unlike diseases such as HLB, leprosis symptoms appear only at mite feeding sites on fruit, branches and leaves. The virus does not spread systemically. On fruit, young lesions are green spots with depressed centers surrounded by yellowish halos. With time, lesion centers will become brown (Figure 1). On the leaves, symptoms appear as lesions on both sides of the leaf with a green center that later turns brown (Figure 2). On branches, early lesions are green, turning a reddish or brown color with an irregular shape, and can cause the bark to peel (Figure 3).
It can be difficult to distinguish between leprosis and canker symptoms on leaves and fruit. Leprosis lesions are usually depressed, while canker lesions are raised. In many cases, leprosis lesions have a zone pattern, which is concentric rings inside the lesion.
If you suspect leprosis, contact your local Florida Department of Agriculture and Consumer Services Citrus Health Response Program office.
Amit Levy is an assistant professor at the University of Florida Institute of Food and Agricultural Sciences Citrus Research and Education Center in Lake Alfred.
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