Protection methods

• During cultivation

There is currently no curative control method that can control viral infections in the field. A plant infected with the papaya ( ringspot virus Papaya ringspot virus ) will therefore remain so throughout its life. At the very beginning of an epidemic, it may be useful to eliminate the first infected plants, particularly in cultivation under cover. However, be aware that viral symptoms are only expressed after an incubation period of one to two weeks, during which time the plant can be a source of virus for aphids. Therefore, when the first symptoms are observed on the first plants, the epidemic may already be developing.

The insecticides are useful to reduce aphid populations, if they are important to plants of culture. Unfortunately, they are generally not effective in preventing the development of PRSV epidemics, as the vectors often come from outside the field, and transmit the virus in very brief bites before the aphicide has even reached. time to act. Sometimes aphid 'hyper-activity' is even observed on the treated plots, which can lead to an even faster development of viral epidemics.

• Next crop

Certain prophylactic measures and cultural practices can limit or delay the development of PRSV epidemics:
- in regions where reservoirs may be present in the environment, weed carefully the plots and their surroundings (edges of hedges, paths, surroundings of shelters, etc.) in order to eliminate sources of viruses and / or vectors ;
- mulch the crops with plastic films (transparent or thermal opaque) which repel aphids. This practice is mainly intended for field crops and can delay epidemics by 2 to 3 weeks, until the foliage covers the mulch, then annihilating its repellent effect for aphids;
- protect nurseries and young plants in the field with non-woven sails (Agryl P17 type) or mesh fabrics (Filbio type). Unfortunately, this type of protection must be removed at flowering, at least partially, so as not to prevent the action of pollinating insects essential for fruit production. The young shoots thus discovered can then be quickly contaminated by aphids. The use of small perforated plastic caterpillars (type 500 holes / m2) is also an effective means of delaying viral epidemics which does not present the constraint of uncorking at flowering, since pollinators can penetrate under the caterpillars. However, this type of cover is not perfectly 'impervious' to aphids and care must be taken to avoid the establishment of colonies of the melon aphid, A. gossypii , which under these shelters find particularly favorable conditions for their proliferation;
- manage the farm space well and avoid planting crops intended for late production near earlier crops which risk being already contaminated. This is particularly important in regions where under-shelter and open-field crops follow one another all year round, such as in the Nice region. In this case, the virus can easily pass from one culture to another, especially if they are close together, and thus persist throughout the year;
- manage time well : if crops succeed one another all year round in a farm or production basin, it may be wise to maintain a period of one to two weeks without Cucurbits to break the viral biological cycle.


A weak strain of PRSV-P made it possible to protect papaya crops very effectively against severe strains by means of premunition *. It has been shown to be much less effective when attempts have been made to use it to protect Cucurbits.

The easiest control method for producers to use is still resistant varieties .
- Melon : there is currently no resistant commercial variety, although excellent resistance governed by the dominant gene Prv is available in genetic resources.
- Courgette : some commercial varieties show varying levels of intermediate resistance to PRSV. These resistances are not total: the plants can be infected, but most often they show only attenuated symptoms.
- Cucumber : Varieties with short fruits or pickles resistant to PRSV are available.