Tangerines are a part of a diverse group of citrus plants known as mandarins. Prized by home gardeners because of their bright color, tangerines prefer warm spaces and a lot of sunlight. With proper cultural care, tangerines suffer few growth problems, but they are afflicted by precisely the same disease problems as other citrus plants, most of which have different characteristics that are helpful for diagnosis.

Alternaria Brown Spot

Alternaria brown spot ailments cause dark spots surrounded by yellowish borders to look on leaves. Sunken dark brown to black spots, also surrounded by a yellow halo, may look on fruit. The stains on infected fruit that remains on the tree eventually become corky. Alternaria brown spot can cause serious leaf and fruit drop. Control can be achieved using a copper fungicide applied to the leaves in the spring when leaves are one-quarter to half expanded and when the leaves have been almost fully expanded. Apply a last spray of fungicide approximately 4 weeks later or after petal fall.

Citrus Scab

Citrus scab (Elsinoe fawcetti) triggers corky increase to develop to the fruit and on shoots and leaves. Fruit lesions begin as pink to light brown pustules, and later resemble cracked nails, turning yellow-brown and then dark grey. The growths can become so many that the fruit is twisted. Control citrus scab having an application of fungicide when leaves have been one-quarter expanded and again at petal fall. Apply a last program 3 weeks after petal fall.

Greasy Spot

Caused by the fungus Mycosphaerella citri, oily spot spores germinate on the undersides of leaves. Then they enter the leaf tissue, causing blisters to form on the undersides of their leaves. Yellow spots develop on the upper leaf surface, followed by brownish blisters on the undersides that darken and become slightly raised using a oily appearance. These oily spots also look on upper leaf surfaces as disease progresses. Defoliation can occur before these symptoms completely develop. To control oily spot, employ copper fungicide and oil when symptoms first appear, and repeat programs in 7 to 10 day intervals as required, thoroughly covering the undersides of their leaves.

Phytophthora Rot

Phytophthora bacterial infection of tangerine trees is caused by the fungal pathogens, P. citrophthora and P. parasitica, which are found in most citrus soils. P. citrophthora is just a winter root rot, while P. parasitica is busy during warm weather. Indicators of infection begin showing as root rot, and peeling bark on crown roots and the spine in the ground level. Reddish brown resin might also be seen oozing from illness places above ground, and girdling of the spine often happens. Phytophthora rot typically results in plant fall symptoms, like yellow chlorosis of leaf veins, defoliation, fruit fall, branch or twig dieback and even death. Soil applications of fungicides containing mefenoxam can control infections if implemented so that treatment coincides with root flushes, which usually begin in early spring. Follow the first program with 1 to 2 more software in 3 month periods. Foliar applications of fungicides containing fosetyl-al can also help manage infections.

See related