Yellow Traps Can Be Used to Monitor Populations of Coccinella transversalis (F.) and Adalia bipunctata (L.) (Coleoptera: Coccinellidae) in Cotton Crops

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Abstract
During 1992–4, square (30 times 30 cm) sticky traps of various colours were used on a commercial cotton farm to trap adults of Coccinella transversalis and Adalia bipunctata which are both major predators of Helicoverpa spp. Both insects were attracted most to yellow traps which also reflected the most visible light between 500 nmand 600 nm(where green foliage reflects most light). When yellow was diluted with white to produce yellow‐white hues, the light reflected between 500 nm and 600 nm was reduced and the numbers of C. transversalis and A. bipunctata adults caught on these traps were also significantly reduced. This suggests that C. transversalis and A. bipunctata adults can discriminate foliage‐like hues (500–580 nm) from non‐foliage‐like hues (580 nm) and are attracted to colours that suggest the foliage of host plants that may harbour their prey. Yellow sticky traps placed 25–50 cm above ground caught significantly more C. transversalis and A. bipunctata adults than those placed at 75–150 cm and are the most appropriate traps to monitor populations of C. transversalis and A. bipunctata adults in cotton farms.