Tobacco sector alerts farmers on disease

FARMERS have been alerted on measures to prevent the Potato Virus Y (PVY) disease that affects tobacco and other solanaceous crops such as potatoes, tomatoes and peppers.

PVY is one of the most damaging diseases of tobacco and can cause up to 70 percent yield loss. It is transmitted primarily through aphids with at least 65 aphid species known to transmit PVY. The green peach aphid (Myzus persicae nicotianae) is the most destructive vector.

PVY is also transmitted when there is a sap exchange between an infected and a healthy plant via wounds. In a statement, the Tobacco Research Board said farmers should rigorously control insect pests, especially aphids, in their crops.

This was why there were such strict rules about when tobacco could be planted and why all crop residue in the field had to be destroyed several weeks before any new seedbeds could be established. This would mean that aphids could not carry disease between seasons.

“Tobacco seed may not be sown before June 1 each year. Tobacco may not be transplanted into the land before September 1 of each year. Tobacco plants in seedbeds must be destroyed before January 1 each year and tobacco plants in the field must be destroyed before May 15 each year,” TRB said adding that there were no tobacco varieties resistant to PVY in Zimbabwe.

“No curative measures are currently available for PVY and currently, there are no tobacco varieties resistant to PVY in Zimbabwe,” said TRB.

The board advised on the measures to take on already affected plants saying: “A few plants that are infected can be uprooted and placed in a sack to avoid infecting healthy plants. They should buried outside the field. Apply some insecticides to kill the vectors and apply Bion to boost plant immunity. Apply some insecticides to kill necrotic veins, banding, bronzing, necrotic spots, and chlorotic rings.”

TRB said they were working on ways to breed for PVY resistance in tobacco varieties but it would take many years to release a PVY-resistant variety. “Trials are underway to evaluate several pesticides for their ability to suppress PVY. Molecular studies on PVY strains present in Zimbabwe will form the basis of future control efforts.”