Protection Methods

- During cultivation

In contrast to fungal diseases, there is no curative method for controlling viruses including potato virus Y (PVY) during cultivation. Generally, an infected plant will remain infected during its lifetime.

If the outbreaks occur in nurseries and are detected early, the plants showing symptoms of PVY should be quickly destroyed (figure 1) and in no case transplanted in the field.

Aphicide treatments are necessary to control aphid populations in tobacco. Unfortunately, they are ineffective for controlling virus outbreaks. Aphids usually come from outside the field and transmit the virus during brief punctures, before an aphicide has time to act. Moreover, the current difficulties observed in controlling aphids on tobacco, are sometimes related to phenomena of insecticide resistance; a situation that does not improve any chance for control of virus outbreaks.

- Next crop

In the case of PVY, the use of resistant varieties is the most effective control measure, particularly in production areas where it is a serious problem.

A few attempts to reduce disease by pre-inoculation with mild pathogenic strains of PVY have been done (cross-protection). They have shown some effectiveness, but this method has not been put into practice in the field.

One should keep in mind and implement all the measures that prevent or at least to minimise the introduction and expansion of PVY in tobacco fields (figure 2). In countries where the infections occur very early, it is necessary to protect nurseries and young plants.  To accomplish this, one may consider using non-woven protection fabrics as a mechanical barrier against aphids.

Careful weeding of nursery plots (figure 3), and their surroundings (hedgerows and paths) should be done to eliminate virus sources and / or vectors. Avoid setting a tobacco crop next to PVY susceptible species, especially other Solanaceae (potato, tomato, and pepper). In France, including Alsace region, this is imperative because potato crops can host PVY strains able to overcome the resistance conferred to tobacco by the va gene. Tobacco and tomato, seem to act as universal hosts of all different strains of PVY.

Advances in molecular biology have opened up exciting opportunities for virus control. This new technology might provide a solution for control of VAM-B related strains. Several new strategies have been developed to control PVY in tobacco. They resulted in transformed plants with genes coding, for viral capsid protein, viral polymerase, viral protease, or random fragments of the viral genome. The resistance induced with these methodologies have different efficiency levels and may be more or less specific to certain strains.

Cross protection against PVY was obtained in transformed tobacco coding for the synthesis of proteins of other viruses. In this case several tobacco lines coding for the capsid protein of LMV showed a high level of resistance to several PVY strains.