Fig mosaic—Fig mosaic virus
Fig mosaic virus infects Ficus benjamina, F. carica, F. lyrata and Cyclamen persicum. In F. carica this viral disease slows tree growth and reduces fruit yield.
Identification
Fig mosaic virus can cause symptoms on both leaves and fruits. On leaves, mosaic spots are distinctly yellow, contrasting with normal green color of the foliage. The margins of the yellow spots blend gradually from a light yellow color into the dark green of healthy tissue. Mosaic spots or lesions may be uniformly scattered over the surface of the leaves or may appear as irregular, scattered patches of pale green. Later in the season, a rust-colored band develops along the border of mosaic spots, apparently caused by the death of epidermal or subepidermal cells.
Life cycle
Fig mosaic is a complicated disease that is not completely understood. The disease has been linked to at least 15 viroids and viruses. Only Fig mosaic emaravirus has been confirmed as a cause of fig mosaic.
Fig mosaic virus is vectored by an eriophyid mite, Aceria fici. These mites are microscopic, 0.003 to 0.005 inch (0.08–0.13 mm) long. They have two pairs of legs near the front (head) end and a wedge-shaped, pale yellow body. Fig mites occur mostly in buds and around the fruit opening. Feeding by a single infectious mite is sufficient to transmit the virus to a healthy seedling of Ficus carica. The virus can also be transmitted by grafting and on self-rooted cuttings from infected trees. The virus is not seedborne or mechanically transmitted, such as on plant-cutting tools.
Damage
Symptoms of Fig mosaic virus consist of various leaf deformities, poor (slow) growth, and yellowing or mottling (mosaic) in the leaves. Pale mottling and deforming of fig leaves may occur on the same twig as normal leaves. Mosaic spots on fruits are similar to those on leaves but are less obvious. Premature fruit drop may occur in certain cultivars. Infected Calimyrna fig trees seem to produce smaller and fewer fruit.
Fruit from some varieties of infected figs (photograph from The American Phytopathological Society) may be discolored, misshapen, undersized, and less abundant. Fruit is most seriously affected when Fig mosaic virus infects the Black Mission cultivar. Calimyrna and Kadota cultivars are less affected. Ficus palmata, or trees derived from seedlings having F. palmata as the male parent, appear to be immune to Fig mosaic virus.
Cyclamen infected with Fig mosaic virus show typical virus-like symptoms. Symptoms include leaf mottling and yellowing, leaf deformation, flower breaking (discolored spots or streaks in blossoms), and slowed plant growth.
Solutions
Obtain plants from a quality commercial supplier. Buy and plant healthy figs that show no symptoms of the disease. Examine young plants carefully for symptoms of mosaic before planting them. Do not propagate from plants showing mosaic symptoms as the virus can be transmitted by vegetative propagation (e.g., cuttings and grafting). Once a fig tree becomes infected with the virus, there is no practical control on residential fig trees. If the tree is not performing satisfactorily, remove and replace it.
Adapted from California Pest Rating Proposal for Fig mosaic virus (PDF), California Department of Food and Agriculture and Pest Management Guidelines: Fig, University of California Statewide Integrated Pest Management Program (UC IPM). |
