Ocorrência de formigas cortadeiras em áreas florestadas com Eucalyptus spp. Nas regiões sul e campanha do Rio Grande do Sul e estudo do controle com iscas das espécies predominantes

Abstract

The state of Rio Grande do Sul has had significant investments in recent years aimed at increasing the area of eucalyptus plantations in the Southern and Campanha regions of the state. These plantations are aimed at producing cellulose and paper, and the main entomological threat they face is the action of various types of leaf cutter ants, each developing its own habits and demanding different control strategies. Among the latter, chemical control still remains the most effective, so that the scope of this work was to identify the different species occurring within the eucalyptus plantations and test a new formula bait insecticide. A survey was conducted in five areas of counties were plantations of this species are conspicuous, Rio Grande, Arroio Grande, Piratini, Pinheiro Machado and Bagé. Collection of specimens was executed along three periods, before planting and for the subsequent two years, extending from May 2006 to March 2008. The efficacy of the formula insecticide was tested on ant nests from the predominant species, seven in total: Acromyrmex ambiguus (Emery, 1887), Acromyrmex heyeri (Forel, 1899); Acromyrmex landolti balzani Emery, 1890; Acromyrmex lundi (Guerin, 1838); Acromyrmex lobicornis (Emery, 1887); Acromyrmex crassispinus (Forel, 1909) and Acromyrmex striatus (Roger, 1863). The species A. lundi and A. lobicornis were graded as low frequency species, however, their presence was recorded at all sites. A. landolti balzani occurred only at the Arroio Grande site, whereas A. lobicornis was found only at locations within the Campanha region. The species A. ambiguus and A. heyeri were the most conspicuous at all times, being A. ambiguus the predominant species in all three sampling dates. The bait insecticide from the De Sangrosse company (sulfluramid 0.3%) exercised an effective control against A.lundi and A. ambiguus, when applied at a dosage of 10g per ant nest, however, for the species A. heyeri its efficacy was low.