One of the pests that causes most damage to horticultural production in general, and specifically in the greenhouses of south-eastern Spain, is Bemisia tabaci or whitefly, which causes a reduction in plant growth and, consequently, losses in production.
Types of damage caused by Bemisia tabaci
Its damage is direct and indirect.
Directs:
- Plant sap suction.
- Formation of black mould on the surface of leaves and other parts, caused by the fungus Cladosporium on honeydew or fly droppings, reducing the photosynthetic surface and therefore the production of photoassimilates.
Indirect:
- Transmission of Tomato yellow leaf curl virus (TYLCV).
Its control is usually carried out with biological and chemical methods, but for it to be more effective, it is necessary to adopt preventive measures, such as placing anti-insects netting in the zenithal and side ventilations of greenhouses. The effectiveness of this practice will depend on the greenhouse airtightness (absence of breaks in the plastic and mesh that could serve as a way for the pest to enter) and on the characteristics of the netting used: number of yarns per cm2, pore diameter, homogeneity of the weave, among others.
It is the size of the netting pores which determines its exclusion capacity. The diameter must be smaller than the diameter of the widest section of the pest’s body. Bemisia tabaci has a thoracic width of 239-320 microns and the width of the abdomen is 565 microns (Bethke, 1990; Cabello, 1996). Therefore, all netting with hole diameters greater than 0.24 mm are not considered suitable for preventing the entry of Bemisia tabaci.
To determine the most effective netting in the laboratory, the pest was introduced into a PVC cylinder, the end of which was covered with the anti-insects netting for analysis purposes. Another cylinder covered with glass was placed on top and all joints were sealed to prevent the fly from escaping. Adults of Bemisia were placed in the first tube and exposed to the sun for one hour. Then, the flies that remained attached to the glass were counted (they were those who managed to pass through the mesh) determining that the most effective netting width for control is 20×10 yarns/cm2 – 50 mesh.
Andalusia Regional Government laws establish the compulsory use of a minimum netting density of 20×10 yarns/cm2 in all ventilation areas, in order to avoid viral diseases transmitted by insects.
It is important that the farmer selects netting which guarantees the correct protection of his crops.
At GreenNets, we manufacture nets with the best raw materials, using state-of-the-art machinery for their manufacture and ensuring the homogeneity of the weaving.
Our innovative Bionet photoselective netting provides extra protection in addition to acting as a physical barrier due to its yarn density (20×10 yarns/cm2 – 50 mesh). Its special optical additives affect the insect’s vision, disorienting it and preventing it from finding a way into the greenhouse.
