The whitefly ('Bemisia tabaci') is possibly the biggest nightmare for tomato growers. This tiny fly is the vector of several of the viral diseases that cause the biggest losses in the sector, including the tomato yellow leaf curl virus (TYLCV). Although resistant-tolerant plants are used in intensive tomato cultivation, considerable damage is still recorded during the periods when the insect's presence peaks.
A group of researchers from the Subtropical and Mediterranean Horticultural Institute (IHSM) La Mayora, whose experimental farm is located in the municipality of Algarrobo, has carried out a study that has lasted three years, and which has made it possible to verify that the use of sustainable strategies can help control the whitefly and the viruses it transmits.
The work and its results have been recently published in the journal 'Plant Disease'. Researchers Francisco Monci, Susana García-Andrés, Sonia Sánchez-Campos, Rafael Fernández-Muñoz, Juan A. Díaz-Pendón and Enrique Moriones, director of IHSM La Mayora, have all participated in it.
According to Moriones, the work's objective has been the search for sustainable strategies to control the negative impact of the TYLCV virus, transmitted by whitefly 'Bemisia tabaci'. On the coast of Andalusia and in warm areas around the world, the damage caused on tomatoes can often be devastating. "These strategies may be particularly relevant for their use in the cultivation of traditional tomato varieties, which are highly susceptible to this virus," said Moriones.
The cultivation of native tomato varieties, whose main quality is their flavor, is attracting more and more producers. An example of this is the Huevo de Toro variety in the Guadalhorce region. The problem is that these varieties do not have resistance to viruses such as the TYLCV; in fact, they are much more sensitive than many of the hybrids that are planted in large areas of Andalusia, such as Almería.
In the work carried out by La Mayora, it has been shown that action can be taken in two ways. On the one hand, in protected crops, it is possible to use plastic covers that are made with ultraviolet light blocking materials (photoselective UV plastics). It has been found that, by doing this, the levels of whitefly detected in the crop are considerably reduced, so there is a decrease in the incidence of virosis, and consequently, a significant increase in the tomato production. "This is because the lack of UV light interferes with the whitefly's vision, limiting its entry into greenhouses and its mobility within them, thus limiting the spread of the virus," explained Moriones.
On the other hand, in tomato crops grown outdoors, it is recommended to use preventive treatments with products inducing acquired systemic resistance, which allows the plant to resist infections. This not only helps reduce the damage caused by this virus, but also leads to increased production.
Even more remarkable is the fact that, according to the study, the combination of the use of UV photoselective plastics and the induction of resistance in protected crops "has shown spectacular results in decreasing viral incidence, with very notable increases in production."
Therefore, the group of researchers says that it may be interesting to employ these sustainable control strategies to control the damages caused by the TYLCV virus, combining them with the use of the tolerant and resistant commercial varieties frequently planted in Andalusia.