Diseases of Satsuma Tangerine Trees

Fruit

• Fungus diseases can damage Satsuma fruits. For example, citrus scab causes unsightly bumps on peels and leaves, resulting in reduced marketability. The fungus overwinters in twigs and unharvested fruit and becomes active during warm spring rains. Melanose overwinters in branches and causes depressed brown spots and streaks on fruit peels. Ripe fruits infected with Phytophthora rot develop brown spots during warm, wet harvest weather.

Leaves

• Diseases that affect Satsuma leaves include greasy spot, which is active during warm, rainy summer weather. This disease causes yellow spots on the upper leaf surface and greasy brown blisters on undersides of leaves. Heavy leaf drop and poor fruit set may occur the following spring and summer. Sooty mold, which causes a black fungus coating on leaves, interferes with photosynthesis and leads to fruit damage. This fungus grows on the sweet liquid secreted by aphids and other sucking insects.

Trunk and Roots

• Fungus diseases, such as Phytophthora foot rot and root rot, affect the roots and the base of the Satsuma tree trunk. The trunk bark peels and oozes a reddish resin near the soil, the roots rot in the soil and the tree has an overall sickly, bare appearance. Girdling of the tree trunk, yellowed leaves, dieback and tree death may occur. Gummosis is a disease that causes hardened discharge on the bark and usually does not harm the tree.

Control

• Sanitation measures, such as dead branch removal and tool sterilization, help protect Satsuma trees from fungus diseases. Copper fungicide applications in the winter, spring and summer control citrus scab, Melanose and greasy spot. Fungicides that contain the compound Aluminum tris help prevent Phytophtora infections during rainy summer weather and horticultural oils control insect pests which cause sooty mold. Early morning irrigation promotes evaporation and prevents root and foot rot. The Texas A&M University Extension states that proper cultural practices are the only necessary control for gummosis.