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Protection methods

  • During cultivation 
There is currently no curative control method that can control viral infections in the field. A plant infected by the virus watermelon mosaic ( Watermelon mosaic virus , WMV) it will remain throughout his life. At the very start 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 WMV 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. We even sometimes observe a "hyper-activity" of aphids on the treated plots, which can lead to an even more rapid development of viral epidemics.


  • Next crops 
Certain prophylactic measures and cultural practices can limit or delay the development of WMV epidemics:
- weed carefully the plots and their surroundings (edges of hedges, paths, approaches to 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 least partially, at flowering, 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 "waterproof" against 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 space well farm and avoid planting crops intended for late production near earlier crops which risk being already contaminated.

The easiest control method for producers to use is still resistant varieties . Unfortunately, concerning the WMV, we are still quite helpless today.
- In melons : there is currently no resistant commercial variety. Research is underway in many countries but so far only partial resistance (also known as intermediate resistance) has been identified in genetic resources. Breeding programs are underway to try to introduce them into commercial varieties.
- In zucchini : there are quite a number of commercial varieties with varying levels of intermediate resistance to WMV. These resistances are not total: the plants can be infected, but most often they show only attenuated symptoms. Commercial transgenic varieties (GMOs) exhibit a very high level of resistance. They provide very good protection against this virus, but can only be used in countries where the legislation allows the cultivation of this type of variety (USA, for example).
- In cucumbers : there is quite a large variability in the sensitivity of commercial varieties to WMV. There is high resistance to this virus in varieties with short fruits or pickles.
Last change : 04/30/21