The effect of plant spacing on the numbers of aphids trapped over the groundnut crop

SUMMARY Aphis craccivora, Aphis gossypii and Longiunguis sacchari were trapped at 3 ft above ground more often over widely‐spaced than over close‐spaced groundnuts. At crop height A. craccivora and A. gossypii showed a similar but greater response to plant spacing. Numbers of Rhopalosiphum maidis and Tetraneura nigriabdominalis caught were not affected by groundnut spacing differences. All aphid species studied except T. nigriabdominalis responded to yellow, but their sensitivity to colour was less during the dry season. It is suggested that the effect of plant spacing on numbers caught was not due to colour alone, but perhaps also to the contrast of plants and soil in widely spaced groundnuts. At crop height, an alighting response was shown only by those species that feed on groundnuts. The control of rosette disease of groundnuts by early planting and close spacing appears to be due to the inhibition of the landing response in A. craccivora by the continuous ground cover resulting from these treatments.