Influence of weather and plant cutting on aphid population (Homoptera: Aphididae) in alfalfa crop (Medicago sativa L.) in Lavras county, Brazil

Abstract

This work was carried out with the objective of determining the influence of climatic factors (temperature, relative umidity and precipitation) and of plant cutting on aphids population in alfalfa crop cv. Crioula. The survey was done weekly from March/1993 to February/1994. Four species of aphids were found: Therioaphis trifolii f. maculata, Acyrthosiphon kondoi, Acyrthosiphon pisum and Aphis craccivora. A tendency of T. trifolii f. maculata to occur in temperatures about 25°C and weekly rainfall under 50 mm, with a peak in December, was observed. The two Acyrthosiphon species, in contrast, occurred in temperatures about 18°C, with a populational peak in August, when no precipitation happened. After the cutting of plants, the number of aphids collected reduced markedly, but this number increased rapidly afterwards.