Ecology, epidemiology

• Conservation

The cucumber mosaic virus ( Cucumber mosaic virus , CMV) is present worldwide. Some strains are more adapted to hot climates (Mediterranean or tropical) while others develop better in cooler climates (temperate regions of northern Europe). The virus infects many botanical species (more than 1000 identified to date), annuals or perennials, both cultivated (tomato, pepper, lettuce, spinach ...) and spontaneous (sow thistle, purslane, capselle, nightshade, stellate). The latter, as well as certain winter crops, play a very important role in the conservation of the virus during the winter (reservoir plants). In spring, they constitute the sources of viruses, and sometimes also those of vector aphids from which epidemics will start.
 

• Transmission

CMV is transmitted non-persistent by more than sixty species aphid . The aphid-vector is capable of acquiring the virus on an infected plant, or of transmitting it to a healthy plant, during very brief bites , of the order of a few tens of seconds, which are the "test bites" ". These allow the insect to recognize whether the plant on which it has landed is a host favorable to its development. Transmission is possible immediately after acquisition, and the aphid remains able to transmit the disease for tens of minutes or even hours. The aphid quickly loses this ability if it performs test bites or feeding bites. But he can acquire the virus again by carrying out a new test bite on a virus-infected plant. Among the main vector species we can mention the melon aphid, Aphis gossypii, and many species that do not grow on cucurbits, such as the green peach , aphid Myzus persicae , and A. fabae or A. craccivora .

The very high efficiency of this mode of transmission means that the disease can spread in a crop without having observed significant outbreaks of aphids, and these are mainly the "visitor" aphids. (not growing on cucurbits) which disseminate viruses transmitted in a non-persistent way.

The possibility of transmission by root debris from diseased plants has been reported in peppers in soilless cultures, particularly in rock wool cakes; this has not yet been confirmed in cucurbits.

CMV does not appear to be seed-borne in cucumber or melon. Seed transmission has been reported in squash (especially those producing seedless seeds used for oil production). The epidemiological significance of this observation is not well known. CMV can be transmitted by seed in certain weeds such as chickweed.