Florida avocados face a renewed threat from avocado sunblotch viroid (ASBVd). The disease can stunt avocado tree growth, deform fruit and silently spread through groves.
Researchers at the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) are calling on growers, industry partners and the public to remain vigilant and take steps now to contain the disease.
"Avocado sunblotch viroid is an insidious threat to avocado production world-wide and, if not controlled, will result in a loss of fruit production and quality" said Jonathan Crane, a tropical fruit crop specialist at the UF/IFAS Tropical Research and Education Center (TREC).
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The disease is caused by a viroid, one of the smallest known infectious organisms to disrupt a tree's normal growth and fruit production. Avocado sunblotch spreads through root grafts among neighboring trees, contaminated pruning or grafting tools, propagation materials such as budwood and seed and even pollen carried by honeybees. The viroid can reduce crop yields by as much as 80 percent, deform fruit and leave trees weakened or stunted.
Part of the problem, according to UF/IFAS experts, is that infected trees may look healthy for years. When symptoms appear, they range from streaked or blotched fruit to unusual coloring on stems and leaves or simply a sharp drop in yield. Even trees free of symptoms can quietly spread the viroid through their seeds or pollen.
"Hundreds of grafted avocado trees are being produced to establish orchards in new areas, driving the industry's expansion northward," said Romina Gazis, associate professor of plant pathology and director of the Plant Diagnostic Clinic at TREC. "At the same time, growers are replanting in orchards where trees were lost to laurel wilt. Because our industry relies on seedling-grafted trees, and the seeds themselves may carry the viroid, it's critical to scout and test for its presence to protect new plantings".
Currently, the state does not have an industry program to certify that budwood or seeds are free of the viroid. In the past, Florida growers recognized the symptoms and took steps to control its spread, but without continued vigilance, ASBVd could increase again.
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UF/IFAS scientists urge nurseries to test budwood trees annually, growers to train staff to spot trees with potential ASBVd symptoms and packinghouses to be on alert for fruit showing signs of the disease. Infected trees must be destroyed to prevent them from serving as reservoirs of infection, and equipment should be sanitized.
With timely, strict sanitation practices, including the removal of infected trees and sanitation of equipment and tools, they were able to eradicate the disease from two avocado germplasm collections.
Growers and industry partners seeking information/testing services can contact the UF/IFAS TREC Plant Diagnostic Clinic or the UF/IFAS Tropical Research and Education Center team has a dedicated Avocado Sunblotch Viroid resource website.
For more information:
Lourdes Mederos
University of Florida
Tel: +1 (954) 242-8439
[email protected]
http://www.ifas.ufl.edu