###### Abstract  
Insect-proof screens are a physical method of crop protection against pests whose use is widespread. The hole size must be optimized since too small holes give rise to poorly porous textiles that cause a significant reduction in the permeability of the textiles to air. A common design strategy is to use a rectangular-hole geometry with the aim of limiting the hole width to prevent insect entry and increasing the hole length to increase the hole surface. However, the validity of this approach has not been tested, and indications suggest that it may not be offering the expected results. The results obtained discredit this widely accepted design criterion since they show that, while the hole width is maintained, protective screens lose efficacy as the hole length increases at least in the range of values considered. It is not possible to find an explanation for these results by considering the hole geometry from a two-dimensional point of view. However, when considering the spatial arrangement of the threads, it is understood that the passage surface for the insects is larger than that considered in the orthogonal projection images and that as the hole length increases, the efficacy of the textiles decreases. t +
Footnote †: journal: Applied Sciences  
width of the holes. The interlacing between the two sets of threads gives stability to the textile. The major limitation of the use of protective screens is related to the resistance they offer to the passage of air through their holes. Textiles with low porosity cause significant reductions in the ventilation rate of greenhouses, with all the problems that this entails [12]. This problem is aggravated by the use of very dense screens (with a high number of threads per unit length), which are intended to combat small insect species such as _Bemisia tabaci_ or _Franklinella occidentalis_. To mitigate this drawback, manufacturers have followed a design strategy that consists of manufacturing fabrics with weft threads spaced further apart to reduce the surface area occupied by the solid matrix and increase the porous surface area. Technically, the limit of this design strategy lies in the stability of the textile. In this way, the warp threads are configured like the bars of a cage to prevent the passage of insects, and the weft threads are the ones that structurally stabilize the textile by keeping the separation between the warp threads constant. We have called this design strategy the \"prison effect\". Therefore, from a design point of view, the spacing between the warp threads (which defines the hole width \(L_{px}\)) is given by the dimensions of the smallest pest species whose presence inside the greenhouse is intended to be avoided. With this design strategy, it is possible to alleviate the problem of very dense, low-porosity screens that cause high resistance to airflow while theoretically achieving high efficacies against pests. This approach is also based on the scientific literature since most papers provide a single dimension to characterize the hole size [13; 14; 15]. The pest species chosen to evaluate the efficacy of the textile physical barriers selected is the whitefly _B. tabaci_, which is one of the most important pests worldwide, responsible for significant production and economic losses [16] in greenhouses and outdoor crops. It is a very polyphagous insect [17] of small size that causes direct and indirect damage and is an important vector of viral diseases [18; 19]. In recent decades, the global importance of using this type of agrotextiles as a preventive measure against the pressure of pests as harmful as _B. tabaci_ has grown considerably. However, there has been no previous work evaluating the prison effect as a design criterion, and field observations have not provided the expected results since the efficacy of protective screens has not been as high as theoretically expected [20]. For these reasons, we propose this work to examine the prison effect approach and assess any overlooked variables.