Protection Methods

- During cultivation

There is no curative method to efficiently control alfalfa mosaic virus (AMV) during cultivation. Generally, an infected plant will remain infected during  its whole lifecycle, although symptoms may progressively diminish.

If the infections occur in nurseries and are detected early, the few plants showing AMV symptoms should be quickly eliminated (figure 1) and in no case be transplanted later.

Aphicide treatments are necessary to control aphid populations on tobacco. Unfortunately, they are often ineffective for controlling virus outbreaks. Indeed, 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, which does not improve the situation of controlling AMV.

-  Next crop

A set of measures should be implemented in order to prevent or at least minimise the introduction of viruses in tobacco fields.

In countries where early contaminations occur, it is necessary to protect nurseries and young plants. For this reason, one may use agrotextiles (unwoven fabrics, mesh ...). The mechanical barrier thus delays further contamination.

Careful weeding of nurseries (figure 2), fields and their surroundings (borders, hedges and paths) should be done to eliminate virus sources and / or vectors. Avoid setting up a tobacco crop next to susceptible to AMV crops such as alfalfa, tomato, spinach ...

There are no resistant varieties to this virus. Many species of Nicotiana are susceptible.

The development of molecular biology has opened up fabulous perspectives in virus control. Several strategies have been developed. They yielded in  transformed plants with a viral gene coding for example for capsid protein, a satellite RNA, or viral replicase. If in the case of AMV such transformed genotypes were obtained, none of them has been used extensively in the field.