The installation of Anti-Insect netting in greenhouse vents is one of the main methods for protecting against crop damaging insects.
They are designed to prevent insects from entering the greenhouse and therefore the pore size must be smaller than the size of the smallest harmful insect. However, they also prevent the exit of crop-beneficial insects such as pollinators.
The impact of the aerodynamic characteristics of the netting on the air flow results in variations in the internal temperature distribution.
When choosing Anti-Insect netting, it is crucial to choose high porosity and optimal manufacturing, with a high number of small diameter yarns and a correct design that allows for numerous and homogeneous pores, to guarantee the effect of a physical barrier to the entry of insects while allowing for optimal air circulation inside the greenhouse. Both the diameter of the yarns and their tightness cause significant variations in the air pressure drop.
Improved natural ventilation has a direct impact on the productive capacity of most greenhouses, which in turn improves energy and environmental efficiency.
Studies suggest that for every 1% increase in ventilation area in greenhouses, increases in tomato crop productivity of between 0.9% and 1.1% can be achieved.
Netting degradation due to wear and soiling
Soil accumulation has an important effect on the aerodynamic characteristics of the netting and reduces the natural ventilation capacity of the greenhouse.
Two negative effects have been observed and quantified by comparing the geometrical characteristics of netting before installation and after three to four years of use:
- Degradation of the yarns making up the netting
- Reduction of porosity due to dirt accumulated in pores.
Over time, this degradation results in an average increase in yarn diameter of 3.1%, as well as an average decrease in pore size of 6.2% and 2.3% in the weft (Lpx) and warp (Lpy), respectively. There is a decrease in netting porosity due to yarn degradation by an average of 6.5%, in addition to an average reduction of 20.3% due to dirt accumulation in the pores, making a total porosity reduction of 26.8%.
This decrease in porosity leads to lower greenhouse ventilation rates and is therefore harmful to the greenhouse microclimate.
Therefore, we recommend that Anti-Insect netting installed in areas with hot climates and/or high atmospheric dust are washed monthly with high-pressure water spray. This simple measure improves the natural ventilation capacity of the greenhouse.