Colored shading nets impede insect invasion and decrease the incidences of insect-transmitted viral diseases in vegetable 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 (ChromatiNets (TM)) of equivalent shading capacity, it increased the fruit yield and improved the quality of bell peppers (Capsicum annuum L.) and tomatoes (Solanum lycopersicum L.) (both Solanaceae). We studied the effects of these colored shading nets on the infestation by aphids [Myzus persicae (Sulzer) and Aphis gossypii Glover (both Hemiptera: Aphididae)] and whiteflies [Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae)], and the incidence of the viral diseases transmitted by these insects, for five consecutive years (20062010). These studies were conducted in the semi-arid Besor 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 23x lower than in tunnels covered by the black or red nets. In accordance with the pest results, when the incidences of Cucumber mosaic virus in pepper grown under the black or red nets ranged between 35 and 89%, they were 210x lower under the yellow or pearl nets. Similarly, when the incidences of necrotic Potato virus Y in tomato grown under black or red nets ranged between 42 and 50%, they were 23x lower under the yellow or pearl nets. Also, when the incidences of Tomato yellow leaf curl virus in tomato grown under the black or red nets ranged between 15 and 50%, but they were 24x lower under the yellow or pearl nets. Putative mechanisms of crop protection achieved by the yellow and pearl nets are discussed.