Field analysis of the deterioration after some years of use of four insect-proof screens utilized in Mediterranean greenhouses

Abstract

The installation of insect-proof screens on greenhouse vents is one of the principal methods of protection against harmful insects for crops. Their main disadvantage lies on their negative effects on natural ventilation and greenhouse microclimate, which have been the focus of studies by several authors. However, few works have analysed the effect of accumulated dust and dirt on these screens. The present study has analysed four anti-insect screens, comparing their geometric characteristics before installation and after three to four years of use. Two negative effects have been observed and quantified: deterioration of the threads that make up the screen and reduction of porosity due to accumulated dirt in the pores. This deterioration over time gives leads to a mean increase in thread diameter of 3.1%, as well to a mean decrease in the pore size of 6.2% and 2.3% in the weft (Lpx) and the warp (Lpy), respectively. In fact, the insect-proof screen porosity (φ) decreased due to the deterioration of the threads by an average of 6.5%, in addition to an average 20.3% reduction due to the accumulation of dirt in the pores, making a total reduction in porosity of 26.8%. This decrease in porosity leads to lower greenhouse ventilation rates, and is therefore detrimental for the greenhouse microclimate. Consequently, it is recommended that insect-proof screens in arid areas such as Almería (Spain), with abundant dust suspended in the atmosphere, be washed monthly using water sprayed at high pressure.

Wind Tunnel Analysis of the Airflow through Insect-Proof Screens and Comparison of Their Effect When Installed in a Mediterranean Greenhouse

“…The methodology used to characterise the geometry of the insect-proof screens was developed at the University of Almería [36,37,38]. For each insect-proof screen, three samples of approximately 2.04 cm 2 were analysed.…”

Microclimate evaluation of a new design of insect-proof screens in a Mediterranean greenhouse

“…The above-mentioned negative aspects of the screens may be exacerbated by the accumulation of dust and dirt in the pores of the mesh (Linker et al, 2002;López et al, 2013). Over time the structure of the mesh deteriorates, and López et al (2013) observed that the thread diameter increases by an average of 3.1% and the porosity of the screen suffers a mean reduction of 6.5%.…”

“…Over time the structure of the mesh deteriorates, and López et al (2013) observed that the thread diameter increases by an average of 3.1% and the porosity of the screen suffers a mean reduction of 6.5%. The accumulation of dust and dirt in the insect-proof screens gives rise to a mean reduction in the porosity of the insect-proof screens of 20.3%.…”

“…The accumulation of dust and dirt in the insect-proof screens gives rise to a mean reduction in the porosity of the insect-proof screens of 20.3%. The combined total of these two negative effects (mesh degradation and accumulation of dust) amounted to a 26.8% mean reduction in porosity (López et al, 2013).…”

An Auto-Tuning PI Control System for an Open-Circuit Low-Speed Wind Tunnel Designed for Greenhouse Technology

“…In this context, wind tunnels have emerged as a useful and cost-effective laboratory technique for the improvement of greenhouse structures [ 10 , 11 , 12 ], the study of climate control systems [ 13 , 14 , 15 , 16 ] and the estimation of the aerodynamic parameters of the experimental models. A number of applications of wind tunnels have been described in the literature on greenhouse engineering, including the determination of drag coefficients for horticultural crops [ 17 ], the study of aerodynamic parameters of insect-proof screens [ 2 , 18 , 19 , 20 , 21 , 22 ] and of greenhouse cooling systems [ 13 , 23 , 24 ], the assessment of wind erosion on agricultural soils [ 25 , 26 ] and the analysis of insect flight mechanisms [ 27 , 28 ].…”