The 2009 ASHS Annual Conference

Photoselective shade-netting is an emerging approach in protected cultivation. The photoselective net products are based on the introduction of various chromatic additives, as well as light dispersive and reflective elements into the netting materials during manufacturing. They are designed to selectively screen various spectral components of solar radiation (UV, visible, and beyond), and/or transform direct light into scattered light. The spectral manipulation is aimed to specifically promote desired physiological responses, while the scattering improves the penetration of the modified light into the inner plant canopy.

The photoselective netting concept was studied in bell pepper (Capsicum annuum L.) cultivation in the Negev semi-arid area in Israel during the last four years. All nets were of a similar shading capacity (30-35%) in PAR. The Red, Pearl and Yellow shade nets (ChomatiNets^®) were all found to increase pepper productivity, expressed by the number of fruits produced per plant as well as Ton/Ha, by 15-40%, compared with the traditional black shade net. Although the net holes allow free passage of small pests, the rates of pest infestations and vector-borne viral diseases were affected by the color and reflectivity of the nets. For example, the incidence of an aphid-borne cucumber mosaic virus disease was significantly lower under the Pearl (10 folds) and Yellow (3 folds) nets, compared to black net. Whiteflies penetration and establishment was 2 fold lower under the Yellow, compared to the black net. All tested pests did not distinguish between the Red and black nets. The reduction in viral infection under the Pearl and Yellow nets resulted in higher percentage of export-quality fruit produced under these nets, relative to either the Red or black nets. The photoselective reduction of pest infestation and viral diseases may lead to reduced pesticide application by growers.
In addition, the pepper fruit seem to “remember” its growth shading conditions during post-harvest storage and shelf-life. Thus, fruit harvested from plants grown underneath the Pearl or Yellow nets, and then stored at 7°C for 2 weeks plus 3 days at 20°C (simulating sea transport and marketing to Europe), developed significantly less decay, compared with the fruit grown under the black shade net. The results might reflect a reduced occurrence of fungal spores under the Pearl and Yellow nets, and/or an enhanced natural resistance of the plants grown under these nets to pathogens.  
The photoselective, light-dispersive shade nets provide a new, multi-benefit tool for crop protection.