The cacao swollen shoot virus disease is among the most economically damaging diseases of cacao trees and accounts for almost 15-50% of harvest losses in Ghana. This virus is transmitted by several species of mealybugs when they feed on cacao plants.
The cacao swollen shoot virus disease (CSSVD) was first observed in the Eastern Region of Ghana in 1936 by a farmer and its virus nature was confirmed in 1939.
CSSVD is considered the most economically damaging cacao virus disease that could account for 15-50% yield loss if the severe strains are involved in infections.
The cacao swollen shoot virus (CSSV) is classified as a member of the plant-infecting pararetroviruses in the genus Badnavirus which are with non-enveloped bacilliform particles that encapsulate a circular double-stranded DNA-genome.
Previously, the isolates and strains were grouped according to the severity of symptom expression and geographical origin.
Now, it is known that CSSVD is caused by a complex of Badnavirus species based on their molecular structure.
CSSV affects all parts of the cacao plant. The symptoms seen on the leaves include red vein banding of the immature ‘flush’ leaves, chlorotic vein flecking or banding which may occur in angular flecks, chlorotic vein clearing, and various forms of mosaic symptoms.
The virus causes swellings of the stems (nodes, internodes, tips) and roots.
Some strains also cause infected pods to change shape and become rounder, smaller and with smoother surfaces.
“This virus is a real threat to the global supply of chocolate,” said Professor Benito Chen-Charpentier, a researcher at the University of Texas at Arlington.
“Pesticides don’t work well against mealybugs, leaving farmers to try to prevent the spread of the disease by cutting out infected trees and breeding resistant trees. But despite these efforts, Ghana has lost more than 254 million cacao trees in recent years.”
Farmers can combat the mealybugs by giving vaccines to the trees to…
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