Controle de Acanthoscelides obtectus (Say, 1831) (Coleoptera:Chrysomelidae) em feijão com óleos essenciais e pós-inertes

Abstract

The use of essential oils of plants and inactive powders has been an alternative for the control of plague-insects of stored grains. The objective of this study was to assess the efficiency of essential oils of cloves and thyme and inactive powders on the control of Acanthoscelides obtectus in laboratory conditions. The biotrials were conducted in the laboratory of Insects Ecology which belongs to the Federal University of Pelotas (UFPel-RS). The extraction of the oils was executed by the hidro-destillation method in a Clevenger device, for 4 hours and the design used was the completely randomized, with five re plications, in a 10x8 factorial arrangement (dozes and exposition time) with ten concentrations (20; 10; 5; 2,5; 1,75; 0,75; 0,5; 0,25 and 0,0% and Tween® 5,0%). Each replication was comprised by 10 unsexed insects of A. obtectus. The variables evaluated are as follows: control efficiency and CL50through the Proc Probit analysis. The evaluations were carried out in 1, 2, 3, 12, 24, 48, 72 and 96 hours after the treatment. The results demonstrate that the essential oils of cloves and thyme caused 100% of mortality after 48 and 72 hours, respectively, in the 20% concentration. The Cl50 was estimated in 30,46 µL mL-1for the oil of cloves and 24,93 µL mL-1 for oil of thyme. In the inactive powders trial, the used design was a completely randomized in a factori al arrangement of 13x7 (inactive powders and exposition time), with five replications. The treatments consisted on three types of basalt powders (0,1; 0,3 and 0,5 mm), two types of powder of granodiorite (0,1 and 0,3 mm) and diatomaceous earth in the doses of 2 and 4 kg ton-1and a control, mixed in 20 g of beans and added 10 adult insects not unsexed insects. After 3, 6, 9, 12, 18 and 21 days, the number of alive insects was observed and by the Abbott (1925) equation the efficiency of the inactive powders was calculated. The results allow to conclude that the soil of diatomaceous earth in the doses (2 and 4 kg ton-1) had 100% of mortality and the powders of basalt and granodiorite had 70% efficiency on the control of A. Obtectus and that the mortality of the insects was influenced by the doses and exposition time of the inactive powders. The use of essential oils of Syzygium aromaticum and Thymus vulgaris and inactive powders represent a viable alternative for use in storehouses for the integrated management of A. obtectus.