Photoselective Netting: an Overview of the Concept, R&D and ...

Photoselective Netting: an Overview of the Concept, R&D and Practical Implementation in Agriculture Y. Shahak Institute of Plant Sciences Agricultural Research Organization (ARO) The Volcani Center, Bet-Dagan 50250 Israel Keywords: light-quality manipulation, diffused light, microclimate modification, stress mitigation, solar energy utilization, protected agriculture Abstract The Photoselective Netting represents an innovative agro-technical concept, which upgrades the conventional net covering to a more sophisticated level, beyond its mere protective functions. In collaboration with Polysack Plastics Industries in Israel, we have developed the technological concept, as well as a collection of photoselective (colored) net products, and studied them in numerous crops during the past 16 years. The different ColorNet products (ChromatiNets®) were designed to selectively screen out defined spectral bands of the solar radiation in the UV, and/or visible spectral ranges, concomitantly with transforming direct light into scattered/diffused light. The spectral manipulation is aiming at specifically promoting desired physiological responses, while the light scattering is improving the penetration of the spectrally-modified light into the inner plant canopy, thus increasing the efficiency of light-dependent processes. Additional aspects of the technology relate to photoselective effects on plant pests and diseases. Our studies in ornamental crops revealed pronounced differential responses to photoselective shading, relative to the traditional black shading (at equivalent shading levels). These include stimulated vegetative vigor (under the Red and Yellow nets), dwarfing (Blue), enhanced branching (Grey, Pearl), as well as various effects on leaf size, variegation, time-to-flowering and flower quality. In vegetables (bell peppers, tomatoes), the Red, Yellow and Pearl shade nets were found to markedly increase the productivity, compared with the common-practice covers. The photoselective features of these shade nets also affected the crop infestation by insect-pests and their carried viral diseases, as well as the occurrence of pathogenic fungal diseases. The combined effects resulted in better crop yields, improved fruit quality, and lower susceptibility to decay during post-harvest storage. Netting studies of fruit tree crops, traditionally grown un-netted (e.g. apples, pears, persimmon, table-grapes) revealed multiple benefits of the netting. The photoselective responsive parameters included productivity, water use efficiency, fruit maturation rate, fruit size, and fruit quality. This article is overviewing major breakthroughs achieved in ornamentals, vegetables and fruit crops in Israel, practical applications by growers, and future prospects. INTRODUCTION Modern agriculture is experiencing an increasing need to protect the crops from their cultivation environment. This trend, which is occurring in many parts of the world, is derived from a few concurrent processes. They include, on one hand, global climate changes and their resulting extreme climatic events, urbanization processes that are thrusting agriculture towards less amenable environments, and, on the other hand, the need to meet with the rising market demands for better product quality, reduced chemical applications, food safety, and sustainability of the production processes. Protected cultivation has traditionally been based on greenhouse technologies. The substantial research and development invested in this area for many decades has Proc. Intl. CIPA Conference 2012 on Plasticulture for a Green Planet Ed.: A. Sadka Acta Hort. 1015, ISHS 2014

155

greatly promoted the protected cultivation technologies and their assimilation in modern agriculture. From the most sophisticated, high-tech greenhouses, to the medium-, and low-tech constructions. However, due to their relatively high cost, and their need for climate control within the enclosed houses, the greenhouse technologies are not applicable for all crops. The covering by protective nets, on the other hand, is providing an economically sound alternative, which better applies for large acreage extensive crops. Yet, although cheaper than greenhouses, the netting technology still comes at a cost that needs to be justified. This is where photoselective netting comes to the rescue. By introducing specific spectral filtration and scattering features into the netting materials, we had succeeded to upgrade and sophisticate the technological concept of netting, now making it multi beneficial. The photoselective netting approach was initially targeted towards specifically stimulating desired physiological plant responses, which are regulated by light, and which determine the productivity and product quality. Further values have later been incorporated into the photoselective netting, to additionally include photoselective repelling effects on pest-borne viral diseases, as well on fungal diseases. All these specific effects are added on top of the non-specific, yet also beneficial protective functions of the netting. Thus, the netting is providing physical protection of crops from their environmental hazards, such as excessive solar radiation, hail, wind, frost, and/or flying pests (insects, birds, bats), side by side with its added specific photoselecive functions. The current paper is overviewing several aspects of the photoselective netting technology and its beneficial outcome. MATERIALS AND METHODS A significant number of experimental photoselective nets was produced and tested during the years. We tend to divide the photoselective nets into two groups. The “colored photoselective nets” including the Red, Yellow, Blue, Green nets, while the “neutral photoselective nets” including the Grey, White and Pearl nets. They are produced in different textures (i.e. knitting/weaving design and density, thickness and shape of the threads, mechanical strength, durability), for the different uses (shading, anti-hail, insect proof), and different crops and climates. The spectral composition and light scattering patterns of the experimented nets were measured prior, and during each field trials, as previously described (e.g. Oren-Shamir et al., 2001; Shahak et al., 2004a, b). The microclimate was monitored for each net treatment, as well as many physiological and horticultural parameters. The materials and methods related to the studies reviewed here were described in their related papers. RESULTS AND DISCUSSION Photoselective Netting: a Joint Academy-Industry R&D Effort The photoselective netting technology was developed during the past 16 years by a joint R&D effort of the Volcani Center (ARO) along with Polysack Plastics Industries in Israel (Oren-Shamir et al., 2001; Shahak et al., 2004a, b, 2008; Rajapakse and Shahak, 2007; Shahak, 2008). The R&D process included the following principal steps:  Developing the principal concept and defining potentially desired spectra.  Producing several types of net products (shade nets, hail nets, etc.), of varying spectral filtration properties. Including the Red, Yellow, Blue, Green, Grey and Pearl colored net products, later named ChromatiNets®.  Analyzing and verifying the spectral properties in a simulation net-house at the ARO.  Setting up horticulture research teams for each crop. Each team was composed of research scientists of varying disciplines from the ARO (e.g. horticulture, agricultural meteorology, post-harvest sciences, entomology, virology), researchers from the Peripheral Agricultural R&D Centers (“Mopim”), research assistants, extension specialists and growers. 156

 Recruiting financial support by competitive grants, mostly from the Israeli Ministry of Agriculture and from the relevant grower boards.  Setting up the experimental site at semi-commercial scales for each study. The size of each netted experimental site ranged between 0.5-5 ha. In some cases more than one location was established per crop (e.g. 4 different climate areas for table grapes).  Each research study involved data collection for 3-6 consecutive years.  The best results were/are assessed in commercial scale model plots prior to their practical assimilation by the growers. The model plots are supervised by the Peripheral R&D Centers (Mopim). Along the years, we continuously maintained a dynamic feedback process between the academic research and the industry. Polysack had assigned a plastics chemistry team, along with their agronomy team, for developing new netting products providing the best spectral filtration for the different tested crops, as revealed during the horticultural studies. They also adjusted the net texture, chromophores stability, mechanical strength, and durability to different field conditions. For example, the Pearl, Yellow, and Red nets, which produced most interesting results in many crops, also imposed some stability challenges, to have later been solved by Polysack. Another industrial challenge relates to maximizing the light scattering capacity of these nets. The horticultural advantage of scattered vs. direct radiation was established in studies of netting (Healey et al., 1998; Shahak et al., 2004a, b), as well as greenhouse covers (Hemming et al., 2005, 2008). Thus, the features of the photoselective net products were adjusted and improved along the years, according to the physiological/horticultural results obtained in the different crops, as they came along, and according to feedback from growers and extension specialists to have implemented the research outcome. Photoselective Netting: a Research in Progress Initially, we had focused on ornamental foliage crops, to have traditionally been cultivated under black shade nets of 50-75% shading in the PAR (400-700 nm). The specific, and rather dramatic responses of foliage crops to the spectral modifications of their shaded environments (Oren-Shamir et al. 2001), had encouraged us to extend the photoselective netting studies towards crops that had commercially been grown under low shading nets (30-40% shading). These included several cut-flower and pot-plant crops (Nissim-Levi et al., 2008; Ovadia et al., 2009), as well as vegetables (Shahak, 2008; Shahak et al., 2008b, 2009). Here again, fascinating results were obtained, leading to further challenging the technology in fruit trees, traditionally grown un-netted. Low shading (15-30% shading) photoselective nets of high mechanical strength were developed for this purpose and studied in numerous fruit tree crops, grown in several climatic regions in Israel. The results obtained so far in fruit trees (apple, pear, peach, table grapes, persimmon, avocado and citrus), demonstrated the multi-benefits that can be achieved by the photoselective approach, even under very low-shading nets (Shahak et al., 2004a, b, 2008a; Wachsmann et al., 2013). The horticultural studies of photoselective netting were extended to additionally include entomology and phytopathology aspects. Indeed, certain photoselective shade nets (mostly the Pearl and Yellow nets) were found to distinctly reduce pest-borne viral diseases (Ben-Yakir et al., 2012a, b, c), as well as the occurrence of fungal diseases, both pre- and post-harvest (Elad et al., 2007; Fallik et al., 2009; Goren et al., 2010). The photoselective netting approach is gradually being tested and implemented in an increasing number of crops, grown in a wide range of geographical regions and climatic conditions around the world (e.g. in North and South America, Europe, China). The crops include ornamentals (Leite et al., 2008; Stamps, 2009), vegetables (Lopez et al., 2007; Yan et al., 2011; Ilić et al., 2012), small fruit (Retamales et al., 2008; Dufault et al., 2009; Takeda et al., 2010; Lobos et al., 2012; Takeda, 2012), kiwi, apples, peach (Basile et al., 2008, 2012; Blanke, 2009; Solomakhin and Blanke, 2008; Solomakhin, 2010; Schettini et al., 2011; Bastías, 2011), and more. Consequently, a sub-working group for Photoselective Netting has been established within the frame of ISHS. Side by side 157

with the progress of the technology and research, the practical application of photoselective netting by commercial growers is continuously expanding, worldwide (Ganelevin, 2008). Ornamental Crops 1. Foliage. Photoselective shade-netting of foliage crops, traditionally cultured under black shade nets of 50-80% shading (e.g., Pittosporum variegatum, Fatsia japonica, Monstera deliciosa) was found to promote differential responses, under equivalent PAR intensities. The photoselective responses include stimulated vegetative growth rate and vigor by the Red and Yellow nets, while dwarfing by the Blue net. The Grey net specifically enhanced branching and bushiness, and also reduced leaf size and variegation in Pittosporum (Oren-Shamir et al., 2001; Shahak, 2008). 2. Cut Flowers and Pot Plants. In line with the vegetative responses described above, several cultivars of Lisianthus (Eustoma grandiflorum), sunflower (Helianthus annuus) and Trachelium were found to develop longer and thicker flowering stems under the Red and Yellow shade nets, while shorter stems under the Blue, compared with their equivalent black shade net. Additionally, the Red net induced shorter time to flowering in some species (e.g. Ornithogalum), even when co-applied with the growth inducer, gibberellin GA3 (Ovadia et al., 2009). The extent of responsiveness varied amongst the different species and cultivars (Oren-Shamir et al., 2003; Rajapakse and Shahak, 2007). The highly dispersive Pearl net was reported to enhance branching of Myrtus communis pot plants, while in Crowea ‘Poorinda Ecstasy’ it increased the number of flowers per branch, compared with a black net of the same shading capacity (Nissim-Levi et al., 2008). 3. Physiological Mechanisms. The effects of the Blue, Yellow and Red nets were related to their enriching/reducing the relative content of the blue, yellow and red spectral bands, in line with similar effects reported for photoselective films and artificial illumination (reviewed by Rajapakse and Shahak, 2007). These responses are probably mediated by known photoreceptors and their derived signal transduction pathways. However, the physiological mechanism behind the reduction of apical dominance leading to the enhanced branching under the Grey and Pearl shade nets remains to be solved. We had previously speculated that the branching effect of the Grey net might relate to its distinct absorption in the IR range (Shahak, 2008). This, however, is not the case for the Pearl net. Nissim-Levi et al. had linked the branching effect to light scattering. However, the Grey net has negligible light scattering capacity (Shahak et al., 2004a; Rajapakse and Shahak, 2007). Thus, the branching mechanism remains a mystery for the time being. Vegetables Shade-net protection is commonly used for producing high-quality bell peppers in semi-arid areas, for preventing sunburns and saving on irrigation. We have studied pepper crop performance under the Red, Yellow and Pearl nets in comparison with the traditional black shade nets, at equivalent shading capacity in PAR. The results of five years of studies with 6 different cultivars consistently showed distinct advantage of the photoselective, light dispersive shading over the black shading. In all tested cultivars the number of fruit produced per plant per growing season was 30-40% higher, and the weight yield 20-30% higher under the 3 photoselective nets, relative to the black net. The average fruit size was comparable under all nets. Interestingly, the Red net consistently out-performed the Pearl and Yellow nets with regards to the number of fruit produced per plant. However, the fruit yield of premium quality was highest under the Yellow and Pearl, thanks to their protective effect from pest and virus infestation (see below). Photoselective Pest and Disease Control In addition to its direct effect on the plants, the photoselective filtration of sunlight also affects plant pests and diseases. Even though the holes of the shade nets are large 158

enough to allow free passage of the aphids, whiteflies and thrips, they differentially respond to the different colored shade nets. This was documented in both bell peppers and tomatoes. The penetration of aphids and whiteflies through the Yellow and Pearl nets, and the incidences of these pests borne viral diseases were markedly lower than the Black or Red nets. The Yellow net was proposed to attract these pests, causing them to remain on top of the net for extended periods of time (an arrestment response), thus reducing the efficacy of viral transmission. Pest protection by the Pearl net was related to repellency due to its light reflective capacity, which is significantly more pronounced than the Red and Black nets. Photoselective netting does not provide full pest control, yet it can be incorporated into integrated pest management strategies (Ben-Yakir et al., 2012a, b, c). Post-Harvest Effects and Their Mechanisms One of our most intriguing findings relate to the phenomenon of the “netting memory” which is carried by bell pepper fruit towards their post-harvest storage. In studies conducted on two different cultivars of red sweet bell pepper, we have found that peppers grown under the Pearl and Yellow shade nets, significantly maintained better fruit quality after 15 days storage at 7°C plus 3 days shelf life simulation, compared to the traditional black shade net, or the Red shade net of equivalent shading capacity (35%). Most prominently, the Pearl and Yellow nets reduced decay incidence in both cultivars during two consecutive experimental years, compared to the Black and Red shade nets. The main decay-causing agent was Alternaria alternata. Results further indicated a significant reduction in Alternaria spp. population in the field, under both Pearl and Yellow nets, as evaluated by selective growing medium. Additionally, the Red shade net significantly reduced post-harvest fruit weight loss, compared to the other shade nets, but other quality parameters such as firmness, elasticity and sugar level have not been affected by the colored shade nets (Fallik et al., 2009; Goren et al., 2010). We further found the pre-harvest photoselective/scattered light environment of the Pearl net specifically enhanced the accumulation of anti-oxidants in the fruit, making it more resistant to post-harvest decay (Kong et al., 2012). It is therefore proposed that the “netting memory” evolves from the reduced pathogen development concomitantly with enhanced plant resistance. Both are induced by the scattered/spectrally modified light regime under the Pearl net during the growth season, and both persist during storage and shelf life of the fruit. Netting and Photoselective Netting of Fruit Trees Our studies of low-shading photoselective netting of fruit tree crops (e.g., peach, apple, pear, table grapes) traditionally cultivated un-netted, revealed differential effects of the colored nets on the performance of the orchard/vineyard. The mere net-covering by itself was found to mitigate extreme climatic fluctuations, reduce heat/chill/wind stresses, enhance photosynthesis and canopy development, and reduce fruit sunburns, compared to the un-netted common practice (Shahak et al., 2004a, 2008; Tanny, 2013). On top of that, the photoselective, light-dispersive filtration of sunlight further affects physiological traits in a differential manner, depending on the chromatic properties of each net. The photoselective responsive traits include fruit-set, time-to-harvest (early or delayed maturation), fruit yield, size, color, and internal and external quality (Shahak et al., 2004a, b, 2008; Rajapakse and Shahak, 2007). Water use efficiency of fruit production was recently found to also differentially respond to photoselective netting of citrus (Wachsmann et al., 2013). It is worth emphasizing, that due to the stimulation of vegetative growth under the nets, which in some fruit crops might undesired consequences, the current practical trend is to reduce their shading capacity. Surprisingly, differential responses can be obtained even under very low shading (15-20%) nets, such as the anti-hail photoselective nets (Basile et al., 2008, 2012; Wachsmann et al., 2013).

159

SUMMARY Our view on agricultural netting has broadened during the years of experimentation, to have become an integrative, holistic concept. It includes light regime modifications by the covering nets (photoselective filtration, shading, light scattering and reflection), together with their mitigation of the micro-climate (temperature, humidity and wind velocity), and together with their protection from pests and diseases, and from environmental hazards. All of the above carry joint agricultural implications. Using it wisely, the netting can improve the efficiency of agricultural production: more food, better quality (both pre- and post-harvest), food safety and sustainability, for lesser inputs (water, PGRs, pesticides, fungicides, land). Although major breakthroughs have already been achieved, there is plenty of room in this area for further technological innovations. ACKNOWLEDGEMENTS My collaboration with the past and present Polysack R&D teams (E. Gal, Y. Offir, R. Ganelevin, A. Bachar, Y. Nir) is highly acknowledged, and so is the devoted and productive contribution by my past and present research group members, including K. Ratner, N. Zur, Y. Giller, E.E. Gussakovsky, L. Avraham, and Y. Kong. I am deeply grateful to my many collaborators during the years, without whom the work reviewed here could not have happened. Their names can be found amongst the literature cited below. The research was funded by numerous grants provided by the Chief Scientist of the Ministry of Agriculture and the Israeli Plants Production and Marketing Board. Literature Cited Basile, B., Romano, R., Giaccone, M., Barlotti, E., Colonna, V., Cirillo, C., Shahak, Y. and Forlani, M. 2008. Use of photo-selective nets for hail protection of kiwifruit vines in Southern Italy. Acta Hort. 770:185-192. Basile, B., Giaccone, M., Cirillo, C., Ritieni, A., Graziani, G., Shahak, Y. and Forlani, M. 2012. Photo-selective hail nets affect fruit size and quality in Hayward kiwifruit. Scientia Hort. 141:91-97. Bastías, R.M., Losciale, P., Chieco, C., Rossi, F. and Corelli Grappadelli, L. 2011. Physiological aspects affected by photoselective nets in apples: preliminary studies. Acta Hort. 907:217-220. Ben-Yakir, D., Antignus, Y., Offir, Y. and Shahak, Y. 2012a. Colored shading nets impede insect invasion and decrease the incidences of insect transmitted viral diseases in vegetable crops. Entomol. Exp. et Appl. 144:249-257. Ben-Yakir, D., Antignus, Y., Offir, Y. and Shahak, Y. 2012b. Optical manipulation of insect pests for protecting agricultural crops. Acta Hort. 956:609-616. Ben-Yakir, D. Antignus, Y., Offir, Y. and Shahak, Y. 2012c. Optical manipulations: an advance approach for controlling sucking insect pests. p.249-267. In: I. Ishaaya, S.R. Palli, and R. Horowitz (eds.), Advanced Technologies for Managing Insect Pests. Springer Science+Business Media Dordrecht. Blanke, M.M. 2009. The structure of coloured hail nets affects light transmission, light spectrum, phytochrome and apple fruit colouration. Acta Hort. 817:177-184. Dufault, J.R. and Ward, B.K. 2009. Enhancing the productivity and fruit quality of forced “Sweet Charlie” strawberries through manipulation of light quality in high tunnels. International J. Fruit Science 9(2):176-184. Elad, Y., Messika, Y., Brand, M., Rav David, D. and Sztejnberg, A. 2007. Effect of colored shade nets on pepper powdery mildew (Levillula taurica). Phytoparasitica 35(3):285-299. Fallik, E., Alakali-Tuvia, S., Parselan, Y., Aharon, Z., Offir, Y., Matan, E., Yehezkel, H., Ratner, K., Zur, N. and Shahak, Y. 2009. Can colored shade nets maintain sweet pepper quality during storage and marketing? Acta Hort. 830:37-43. Ganelevin, R. 2008. World-wide commercial applications of colored shade nets technology (ChromatiNet®). Acta Hort. 770:199-203. 160

Goren, A., Alkalai Tuvia, S., Perzelan, Y., Aharon, Z., Fallik, E. and Shahak, Y. 2010. The effect of colored shade nets on sweet bell pepper quality after prolonged storage and shelf life. Acta Hort. 927:565-570. Healey, K. D. Rickert, K. G. Hammer, G. L. and Bange, M. P. 1998. Radiation use efficiency increases when the diffuse component of incident radiation is enhanced under shade. Australian J. Agricultural Research 49(4):665-672. Hemming, S., van der Braak, N., Dueck, T., Elings, A. and Marissen, N. 2005. Filtering natural light by the greenhouse covering - more production and better plant quality by diffuse light? Acta Hort. 711:105-110. Hemming, S., Dueck, T., Janse, J., van Noort, F. 2008. The effect of diffuse light on crops. Acta Hort. 801:1293-1300. Ilić, Z.S., Milenković, L., Stanojević, L., Cvetković, D. and Fallik, E. 2012. Effects of the modification of light intensity by color shade nets on yield and quality of tomato fruits Scientia Hortic. 139:90-95. Kong, Y. Avraham, L., Perzelan, Y., Alkalai-Tuvia, S., Ratner, K., Shahak, Y. and Fallik, E. 2012. Pearl netting affects postharvest fruit quality in ‘Vergasa’ sweet pepper via light environment manipulation. Scientia Hort. 150:290-298. Leite, C.A., Ito, R.M., Lee, G.T.S., Ganelevin, R., Fagnani, M.A. 2008. Light spectrum management using colored nets to control the growth and blooming of Phalaenopsis. Acta Hort. 770:177-184. Lobos, G.A., Retamales, J.B., Hancock, J.F., Flore, J.A., Cobo, N. and del Pozo, A. 2012. Spectral irradiance, gas exchange characteristics and leaf traits of Vaccinium corymbosum L. ‘Elliott’ grown under photo-selective nets. Env. Exp. Botany 75:142149. Lopez, D., Carazo, N., Rodrigo, M.C. and Garcia. J. 2007. Coloured shade nets effects on tomato crops quality. Acta Hort. 747:121-124. Nissim-Levi, A., Farkash, L., Hamburger, D., Ovadia, R., Forrer, I., Kagan, S. and OrenShamir, M. 2008. Light-scattering shade net increases branching and flowering in ornamental pot plants. J. Hort. Sci. Biotech. 83:9-14. Oren-Shamir, M., Gussakovsky, E.E., Shpiegel, E., Nissim-Levi, A.,Ratner, K., Ovadia, R., Giller, Y.E., Shahak, Y 2001. Coloured shade nets can improve the yield and quality of green decorative branches of Pittosporum variegatum. J. Hort. Sci. Biotech 76:353-361. Ovadia, R., Dori, I., Nissim-Levi, A., Shahak, Y. and Oren-Shamir, M. 2009. Coloured shade nets influence the stem length, time to flower and flower size of ornamental crops. J. Hort. Sci. Biotech. 84(2):161-166. Rajapakse, N.C. and Shahak, Y. 2007. Light quality manipulation by horticulture industry. p.290-312. In: G. Whitelam and K. Halliday (eds.), Light and Plant Development. Blackwell Publishing, UK. Retamales, J.B., Montecino, J.M., Lobos, G.A. and Rojas, L.A. 2008. Colored shading nets increase yields and profitability of highbush blueberries. Acta Hort. 770:193-197. Schettini, E., De Salvador, F.R., Scarascia Mugnozza, G. and Vox, G. 2011. Evaluation of coloured nets in peach protected cultivation. Acta Hort. 893:235-242. Shahak, Y., Gussakovsky, E.E., Cohen, Y., Lurie, S., Stern, R., Kfir, S., Naor, A., Atzmon, I., Doron, I. and Greenblat-Avron, Y. 2004. ColorNets: a new approach for light manipulation in fruit trees. Acta Hort. 636:609-616. Shahak, Y., Gussakovsky, E.E., Gal, E. and Ganelevin, R. 2004a. ColorNets: crop protection and light-quality manipulation in one technology. Acta Hort. 659(1):143151. Shahak, Y. 2008. Photoselective netting for improved performance of horticultural crops. A review of ornamental and vegetable studies carried in Israel. Acta Hort. 770:161168. Shahak, Y., Ratner, K., Giller, Y.E., Zur, N. Or, E., Gussakovsky, E.E., Stern, R., Sarig, P., Raban, E., Harcavi, E., Doron, I. and Greenblat-Avron, Y. 2008a. Improving solar energy utilization, productivity and fruit quality in orchards and vineyards by 161

photoselective netting. Acta Hort. 772:65-72. Shahak, Y., Gal, E., Offir, Y. and Ben-Yakir, D. 2008b Photoselective shade netting integrated with greenhouse technologies for improved performance of vegetable and ornamental crops. Acta Hort. 797:75-80. Shahak, Y., Ratner, K., Zur, N., Offir, Y., Matan, E., Yehezkel, H., Messika, Y., Posalski, I., and Ben-Yakir, D. 2009. Photoselective netting: an emerging approach in protected agriculture. Acta Hort. 807(1):79-84. Solomakhin, A. and Blanke, M. 2008. Coloured hailnets alter light transmission, spectra and phytochrome, as well as vegetative growth, leaf chlorophyll and photosynthesis and reduce flower induction of apple. Plant Growth Regulator 56:211-218. Solomakhin, A. 2010. The microclimate under coloured hailnets affects leaf and fruit temperature, leaf anatomy, vegetative and reproductive growth as well as fruit colouration in apple. Annals of Applied Biology 156(1):121-136. Stamps R.H. 2009. Use of colored shade netting in horticulture. HortScience 44(2):239241. Takeda, F., Glenn, D.M., Callahan, A., Slovin, J. and Stutte, G.W. 2010. Delaying flowering in short-day strawberry transplants with photoselective nets. International J. Fruit Science 10(2):134-142. Takeda, F. 2012. New methods for advancing or delaying anthesis in short-day strawberry. Acta Hort. 926:237-241. Tanny, J. 2013. Microclimate and evapotranspiration of crops covered by agricultural screens: a review. Biosystems Engineering 114(1):26-43. Wachsmann, Y., Zur, N., Shahak, Y., Ratner, R., Giler, Y., Schlizerman, L., Sadka, A., Cohen, S., Garbinshikof, V., Giladi, B. and Faintzak, M. 2013. Photoselective, antihail, netting for improved citrus productivity and quality. Acta Hort. 1015:169-176. Yan, Q.Y., Liu, H.C., Chen, R.Y., Song S.W. and Sun G.W. 2011. Effects of different shading-net on growth and quality of flowering Chinese cabbage. Acta Hort. 907:199-203.

162