Dinâmica populacional da ácarofauna em agroecossistema ervateiro, no município de Dois Vizinhos, PR

Abstract

The advance and spread agricultural frontiers and the necessity to meet the needs of market has lead to a change in the mate-tea growth system in the Southern region of Brazil. Pest problems, previously unnoticed in the extraction system, have increased in importance, due to the implantation of single vegetable species, which has lead to the simplification of the environment, with increasingly larger economical losses. More than eighty animal species feed from different parts of the mate-tea plant. A good management is crucial and it should take into consideration the several factors relevant to this peculiar environment, so that disturbances do not promote populational explosions of some of these species. In the event of any such unbalance, the result would be increased cost and decreased quality of the product. In the context, this study was conducted in Dois Vizinhos town, in the State of Paraná, with the objective of studying the phytophagous mites and their population dynamics, as well as that of their natural predators. For this reason, leaf samples from different parts of the plant have been taken, and the number of mites was counted. This research has been done from August 2001 to July 2002. During this period, two species of phytophagous mites, Dichopelmus notus Keifer, 1960 and Oligonichus yothersi (McGregor), 1914, and three species of predators identified as Euseius concordis (Chant, 1959), Iphiseiodes zuluagai Denmark & Muma, 1972and Agistemus sp. were related to the mate-tea plant. The D. notus mite has appeared in large numbers in mature leaves and in the inferior face of leaves. It was more frequent in the inferior part of leaves belonging to the inferior and medium stratum and in leaves from the internal canopy. On the other hand, O. yothersi has mainly occurred in mature leaves, in their superior face. The concentration of E. concordis e I. zuluagai has been larger in the inferior face of the leaves belonging to the inferior and medium stratum, as well as in the inferior face of the leaves in the internal canopy region, and in the inferior face of mature leaves. D. notus, O. yothersi, E.concordis and I. zuluagai mites have attained the ir highest population numbers in periods of mild temperatures and little rain precipitation. In leaves from the external canopy, the largest population density of Agistemus sp. has occurred in periods of high temperature and heavy rain. There was indication of mutual influence between these species.