Colored shading nets reduce insect born viral diseases in vegetable crops

From 2006-2010 we studied the effects of colored nets on infestations by aphids and whiteflies and on the incidence of the viral diseases they transmit. All studies were conducted in southern Israel and plants were grown in ‘walk-in’ tunnels that were covered with various shading nets. Pests were monitored using yellow sticky traps and counts on the plants. Viral diseases were determined by visual symptoms, immunological assay of leaf or fruit extracts and RT-PCR. Although the shading nets permitted free passage of the pests, the infestation levels of aphids and whiteflies in tunnels covered by the Yellow and Pearl nets were consistently 2-3 folds lower than in tunnels covered by the Black net. In pepper, when the incidences of cucumber mosaic virus (CMV) under the Black net were 35-89%, they were 2-10 folds lower under the colored nets. In tomato, when the incidence of necrotic potato virus Y (PVY) under the Black net was 42%, it was 2-3 folds lower under the colored nets. When the incidences of tomato yellow leaf curl virus (TYLCV) under the Black net were 15-50%, they were 2-4 folds lower under the colored nets. Levels of pests and incidences of viral diseases under the Red net were similar to those under the Black net. Possible mechanism for the protection by the Pearl net is deterring alighting of pests due to high reflection. Possible mechanism for the protection by the Yellow net is arresting response of pests.