Protection Methods

- During cultivation

There is no curative method to effectively control tobacco etch virus (TEV) during cultivation. Generally, an infected plant will remain infected during its entire lifecycle.

If attacks occur in nurseries and are detected early, the few plants showing symptoms of TEV should be quickly eliminated and in no case transplanted later.

Aphicide treatments are necessary to control aphid populations on tobacco. Unfortunately, they are often ineffective for controlling virus outbreaks. The reason is that aphids often come from outside the field and transmit the virus during brief punctures, frequently before the aphicide has time to act. Moreover, the current difficulties in controlling aphids on tobacco, are sometimes linked to insecticide resistance. This resistance does not improve the situation.

- Next crop

For TEV management, the use of resistant varieties would be the most effective way of control, particularly in production areas where it occurs severely. A few Burley varieties such as Kentucky 10, Kentucky 14, Burley 21, show some field tolerance to TEV. This resistance is very partial and is not comparable to that presented by TN 86. Three other genotypes (Virgin A Mutant = VAM, SOTA 6505E  and Havana 307) might have a resistance comparable to that of TN 86. In our knowledge, few breeding programs in the United States use Havana 307 as a parent. This resistance is controlled by a few genes, perhaps two. The same genotype was resistant to two other potyviruses: PVY and TVMV.

It is interesting to note that  TN 86, VAM, SOTA 6505E and Havana 307 are resistant also to PVY. They possess the recessive va gene (see the fact sheet of potato virus Y). In addition, it appears that the gene or genes that confer resistance to TEV are allelic, at least in three of these genotypes. One may wonder whether there is a certain relationship between the presence of the single va gene and the resistance of tobacco to these three potyviruses. If so, many varieties resistant to PVY are also resistant to TVMV and TEV.

Keep in mind and utilise all the measures that tend to prevent or at least, minimise the introduction of TEV and its extension in tobacco fields

In countries where contaminations occur very early, nurseries and young plants must be protected with use of agrotextiles (unwoven fabrics, mesh ...). The mechanical barrier thus created delays contamination.

Careful weeding of nurseries (figure 1), plots and their surroundings (hedgerows and paths) should be created to eliminate virus sources of and / or vectors.

Avoid planting a tobacco crop next to susceptible to TEV species, especially Solanaceae (in particular pepper and tomato, to a lesser extent potato).

Advances in molecular biology have opened up new opportunities in virus control. Several new strategies have been developed. They resulted in transformed plants with genes coding, for viral capsid protein, a satellite RNA, or viral replicase. If in the case of TEV such transformed genotypes were obtained, none of them has been used extensively in field.