Insects use optical cues for host finding and flight orientation. The hue, brightness, size, shape and contrast of the visual cue affect the insect response. Manipulation of the natural optical cues can interfere with host finding and dispersal of insect pests. Sucking insect pests, such as aphids and whiteflies, cause great economic losses for growers of agricultural crops worldwide. These pests cause direct feeding damages and they often transmit viruses to crop plants. Non-persistent viruses must be transmitted within minutes to 2 hours after aphids acquired them. These insects have receptors for UV light (peak sensitivity at 360 nm) and for green-yellow light (peak sensitivity at 520-540 nm). The absence of UV deters these pests and decreases their dispersal rate. Yellow color induces landing and favors settling of these insects. High level of reflected sunlight (above 25% of sun radiation) deters landing of these insects. Thus, optical cues can be used to divert pests away from crop plants. This can be achieved by incorporating optical additives to cladding materials (plastic sheets, nets and screens above plants). For non-persistent viruses, any delay of the infected aphids with an arresting color can reduce the efficacy of viral transmission. Results of our studies indicate that optical manipulation can reduce the infestation levels of aphids and whiteflies and the incidence of viral diseases they transmit by 2-10 folds. Thus, optical manipulations can be a part of integrated pest management programs for protected crops.

Sucking insect pests, such as aphids, whiteflies and thrips, cause great economic losses for growers of agricultural crops worldwide. These pests inflict direct feeding damages and they often transmit pathogenic viruses to crop plants. These pests use reflected sunlight as optical cues for host finding. The optical properties, size, shape, and contrast of the color cue greatly affect the response of these pests. Therefore, manipulation of optical cues can reduce the success of their host findings. These pests are known to have receptors for UV light (peak sensitivity at 360 nm) and for green-yellow light (peak sensitivity at 520-540 nm). Green-yellow color induces landing and favors settling (arresting) of these pests. High level of reflected sunlight (glare) deters landing of these insects. We propose to use optical cues to divert pests away from crop plants. This can be achieved by repelling, attracting and camouflaging optical cues. The manipulating optical additives can be incorporated to mulches (below plants), to cladding materials (plastic sheets, nets and screens above plants) or to other objects in the vicinity of the plants. Cladding materials should contain selective additives that let most of the photosynthetically active radiation (PAR) pass through and reflect the wavelengths that sucking pest perceive. Results of our studies indicate that optical manipulation can reduce the infestation levels of sucking pests and the incidences of viral diseases they transmit by 2-10 folds. Delay of the aphids infected with non-persistent viruses that must be transmitted within minutes to 1-2 hours by arresting colors is expected to reduce the efficacy of viral transmission. This technology can be made compatible with the requirements for plant production and biological control. Optical manipulations can become a part of integrated pest management programs for both open field and protected crops.

Black shading nets are commonly used to protect agricultural crops from excessive solar radiation and wind, and for water saving. Recent studies have demonstrated that when black nets were replaced by either red, yellow, or pearl nets ( C hromati N ets ™ ) of equivalent shading capacity, it increased the fruit yield and improved the quality of bell peppers ( C apsicum annuum L .) and tomatoes ( S olanum lycopersicum L .) (both S olanaceae). We studied the effects of these colored shading nets on the infestation by aphids [ M yzus persicae ( S ulzer) and A phis gossypii Glover (both H emiptera: A phididae)] and whiteflies [ B emisia tabaci ( G ennadius) ( H emiptera: A leyrodidae)], and the incidence of the viral diseases transmitted by these insects, for five consecutive years (2006–2010). These studies were conducted in the semi‐arid B esor region in southern Israel. The plants were grown in ‘walk‐in’ tunnels that were covered by several nets of 35% shading capacity in the range of photosynthetically active radiation. Although the shading nets permit free passage of these pests, the infestation levels of aphids and whiteflies in tunnels covered by either the yellow or pearl nets were consistently 2–3× lower than in tunnels covered by the black or red nets. In accordance with the pest results, when the incidences of C ucumber mosaic virus in pepper grown under the black or red nets ranged between 35 and 89%, they were 2–10× lower under the yellow or pearl nets. Similarly, when the incidences of necrotic P otato virus Y in tomato grown under black or red nets ranged between 42 and 50%, they were 2–3× lower under the yellow or pearl nets. Also, when the incidences of T omato yellow leaf curl virus in tomato grown under the black or red nets ranged between 15 and 50%, but they were 2–4× lower under the yellow or pearl nets. Putative mechanisms of crop protection achieved by the yellow and pearl nets are discussed.

Colored shade nets, which have been developed during the last decade to filter selected spectral regions of sunlight, concomitantly with inducing light scattering, are designed to specifically modify plant behavior. Crops grown under various colored (photo-selective) shade nets (ChromatiNets (TM)) were found to improve their fruit yield and fruit quality. In the study described here, we have found that pepper grown in an arid region under red and yellow shade nets, had a significant higher yield compared with black nets of the same shading factors, without reducing fruit size. In addition, the export-quality fruit yield was also significantly increased under the red and yellow shade nets. Our results from 2007 further showed that the photo-selective nets, especially the yellow shade net, maintained better the pepper fruit quality, as was evaluated by several quality parameters. Most prominently, it lowered the decay incidence at the end of storability and shelf-life simulation. The results suggest the advantage of growing pepper under light-dispersive photo-selective shade nets, rather than the traditional black nets, for improving productivity, quality and probably also, shelf-life. The latter requires further verification.

Photoselective nets were designed to selectively filter different spectral bands of solar radiation, and/or transform direct light into scattered light. The spectral manipulation intends to specifically promote desired physiological responses, while the scattering improves the penetration of the spectrally-modified light into the inner plant canopy. The current paper reviews the photoselective concept and its assessment in various crops. It further describes a recent study on photoselective shade-netting of bell peppers, demonstrating the potential uses of this technology for improving both crop performance and pest control. Thus, the replacing of the traditional black shade net by either a Red, Yellow or Pearl nets (ChromatiNets (TM)) of similar shading factors, resulted in 15-40% higher fruit production in different cultivars. The major response to the photoselective filtration was producing more fruits per plant, with essentially no reduction of fruit size or quality. Additional benefits relate to photoselective improvement of pest control. The Yellow shade net decreased whiteflies penetration and establishment by 2-3 folds compared to black nets, even though the net holes were large enough to allow free passage of the pests. The incidence of an aphid borne cucumber mosaic virus (CMV) disease was significantly lower under white, Pearl and Yellow shade nets compared to black or Red nets. Additionally, a photoselective 50 mesh screen (OptiNet (R)) reduced thrips infestation 3-4 folds relative to the standard screen. The photoselective, light-dispersive shade nets and screens provide a new tool for improving both crop performance and pest control.

Photoselective shade-netting is an emerging approach in protected cultivation. The photoselective net products are based on the introduction of various chromatic additives, light dispersive and reflective elements into the netting materials. They are designed to selectively screen various spectral components of solar radiation (UV, PAR 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. Additional potential benefits relate to photoselective effects on plant pests, beneficial insects or diseases. Studies of ornamental crops, traditionally grown in shade-net houses, revealed distinct responses to the red, yellow, blue, grey and pearl nets, compared with common black nets of the same shading factor. These include stimulated vegetative vigor, dwarfing, branching, leaf variegation and timing of flowering. The photoselective netting concept was further tested in vegetable cultivation in either net-houses, or in combination with insect-proof nets or greenhouse plastic film covers. The red and pearl nets repeatedly increased the productivity of leafy crops, bell peppers and ornamentals, compared with each crop's standard cover. Although the shade-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 nets. Whiteflies penetration and establishment was 2 fold lower under the Yellow net compared to the black net. The photoselective, light-dispersive shade nets provide a unique tool that can be further implemented within protected cultivation practices.

Thrips and whiteflies are major pests of vegetables and flowers grown under protective structures. Plastics or screens containing photo-selective additives have been shown to reduce the risk for infestation by these pests. We tested the protection against thrips provided by screens with photo-selective additives that are being developed under the trade mark OptiNet (R). Our studies were conducted in southern Israel from 2002 to 2005. In walk-in tunnels, thrips infestations on cucumber, tomato and chive plants under OptiNet a (both of 40 and 50 mesh) were 3 to 4 folds lower than under a standard 50 mesh screen. This protection against thrips was further enhanced by weaving of narrow aluminum foil strips into the OptiNet (R). Thrips preferred landing on yellow and blue shading nets (ChromatiNet (R)) over black and red nets. Whiteflies preferred landing on yellow shading nets over black, blue and red nets. Covering plants with yellow nets did not increase, but rather decreased, the risk of whiteflies penetration and establishment. Covering with yellow or blue nets did not increase the risk of thrips penetration and establishment. It appears that these pests remain on their preferred colored nets for a long time (an arrestment response), and as a result they are less likely to infest the plants underneath.