Influência de cortes na cultura da alfafa (Medicago sativa) sobre a flutuação populacional de ninfas e adultos de pulgões (Homoptera: Aphididae)

Abstract

An. Soc. Entomol. Brasil 26(2): 265-275 (1997) Influence of the Plant Cuttings in Alfalfa (Medicago sativa ) Crop on the Population Fluctuation of Nymphs and Adults of Aphids (Homoptera: Aphididae)ABSTRACT -Population dynamics of Therioaphis trifolii (Monell) forma maculata, Acyrthosiphon kondoi Shinji and Acyrthosiphon pisum (Harris) was studied in alfalfa (Medicago sativa) crops for hay production at Universidade Federal de Lavras, Minas Gerais, after 14 cuts, between March, 1993 and March, 1995. Fall and winter were the most favorable seasons for the three species; T. trifolii f. maculata doubled its population from 1st to 2nd year, A. pisum and A. kondoi maintained the same population level. The number at the some age was similar to the three species of aphids, ranging from 64% to 78% for nynphs of the 1st and 2nd instars; from 18% to 26% for 3rd and 4th instars; and from 4% to 10% for adults. Alate occurred in low densities (15%) compared to nymphs of 3rd and 4th instars and adults, always associated to high population densities.There was an overall decrease in the populations of aphids after each cutting, followed by a recovery associated with the development of plants and weather conditions.KEY WORDS: Insecta, Therioaphis trifolii forma maculata, Acyrthosiphon kondoi, Acyrthosiphon pisum.