Ecology, epidemiology

Conservation, sources of viruses

The cucumber mosaic virus ( Cucumber mosaic virus , CMV) can infect more than 800 species representing 85 botanical families belonging to monocots such as the broadleaf weeds. Market gardening and ornamental crops (perennial and perennial) are particularly affected.

Among spontaneous plants, species as common as purslane, black nightshade, groundsel, sow thistle, wild lettuce, dead nettle, speedwell, madder, mercurial ... are infected.

In summer, in addition to many weeds, crops such as cucurbits, tomatoes and peppers, spinach such as celery in winter, can play this role, but it is above all the weeds that ensure the maintenance of the virus. 'from one season to the next on and near the plots. In addition, some species, such as the chickweed, are able to transmit the virus by seed to their offspring.


- Transmission, dissemination

CMV is transmitted by aphids in the non-persistent mode. The aphid vector can acquire the virus on an infected plant and transmit it to a healthy plant, in a few seconds, during very brief bites, called "test bites". These allow him to ensure that the plant is a favorable host for its development. The aphid is able to transmit the virus immediately after its acquisition and remains so for about ten minutes. He loses this ability if he performs other ordeal bites or food bites. The proportion of plants that it risks contaminating is greatest in the vicinity of the source plant. Carried by the wind, it can be a formidably efficient vector over relatively large distances. About sixty species of aphids, including Myzus persicae or Aphis gossypii , are susceptible to transmitting CMV.

As in almost all cultivated species, the virus is not transmitted by seed in lettuce.

The very high efficiency of its mode of transmission means that the spread of this virus can be very rapid without having observed significant outbreaks of aphids. Several abiotic factors play a big role in the biology and efficiency of aphid flights:
- the wind conditions their distribution;
- the temperature acts on the growth of lettuce, the multiplication of the virus and the development of aphid colonies;
- the culture environment. The proximity of other sensitive crops and contaminated weeds in particular promote contamination.

To these factors, it is advisable to add regional parameters such as the arrangement of the plots, the protection of crops against the prevailing winds by hedges, the local climatic conditions and their influence on certain reservoir plants ...