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Relay Intercropping: Effect on Predators in Cotton

R. Montandon, J.E. Slosser


Relay intercropping of winter and spring strip crops with cotton was used to illustrate conservation and amplification of predators in a three-year study in the Texas Rolling Plains. Numbers of aphids and aphid predators in cotton isolated from other crops were compared to those where wheat, canola, sorghum (intercrops), and cotton were planted adjacent to each other and overlapped temporally. The intercrops "relayed" aphid predators from canola and wheat in the winter, to sorghum in the spring, and to cotton in the summer. Predators appeared in high numbers earlier in the summer in relay than in isolated cotton. The three-year average of predator numbers exceeded 20 per meter by 4 August in relay cotton, but not until 2 September in isolated cotton. Predator numbers in relay cotton were higher than in isolated cotton until late August when aphid populations in relay cotton declined. Predator numbers in isolated cotton (where aphid densities were still accelerating) became higher after late August. Aphid abundance was lower in relay than in isolated cotton. The three-year average of aphid abundance in relay cotton never exceeded 1,932 aphids/10 leaves on any one sample date, but it reached 4,898 aphids/10 leaves in isolated cotton. The most commonly encountered group of predators in cotton were lady beetles (67.2% of the total number of predators).

Reprinted from Proceedings of the 1996 Beltwide Cotton Conferences pp. 786 - 788
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998