Uso do óleo essencial de ageratum conyzoides l. (asteraceae) no controle do callosobruchus maculatus (fabr., 1775) (coleoptera: chrysomelidae: bruchinae

Abstract

The weevil Callousbruchus maculatus (Fabr.) (Coleoptera: Bruchinae), cowpea plague of Vigna unguiculata (L.) Walp., (Fabaceae), is classified as the main internal primary pest for causing economic losses during storage. In storage units the control is usually done by purging or fumigating. Due to the need to implement alternative control, studies of secondary compounds obtained from plants with fumigant and repellent properties have been widely disseminated, aiming at the control of stored grain pests, mainly with essential oils and vegetable powders. Thus, the objective of this work to assess the toxic effect and the essential oil repellent action of Ageratum conyzoides mentrasto (Asteraceae), as well as the extraction yield and chemical characterization, for weevil control C. maculatus. For the fumigation test, were used glass containers of 1.3 L capacity were used, where 20 adults of C. maculatus, 0-24 h of age, were not confined. After 48 h was rated the percentage of mortality. In the contact test, glass containers with 40 g of cowpea were impregnated with the different concentrations of the essential oil (treatment) and without essential oil (control), adding 16 unsexed adults of C. maculatus with 0-24 h of age. After 48 h of confinement, the percentages of mortality were determined. After 48 h of confinement, the percentages of mortality were determined. For the repellency experiment, sands composed of three linearly interconnected glass containers were used, and 20 g of cowpea beans were added to the container at the extremities, constituting on one side the vessel without treatment (control) and on the other side, the treatments and, in the central container were released 16 not sexed adults of C. maculatus with age varying from 0-24 h. After 48 h of confinement, were certain percentages of mortality. For the experiment of used repellency arenas consisting of three interconnected linearly glass containers, being containers of 20 g of added cowpea beans as a side the container without treatment (witness) and on the other side, the central container and treatments were released sexed not 16 adults of C. maculatus sexed not with age ranging from 0- 24 h. After 48 h, the bugs contained in each container were quantified, for the evaluation of repellency through formula: Irs = 2 G/(G + P). The test of fumigation the LC50 of 0.698 μL/40 g of grain and LC95 of 6.066 μL/40 g of beans. To contact test the lethal concentration to kill 95% of the population (LC95) was 11.433 μL/40 g of grain and sub lethal (LC50) corresponded to 1.675 μL/40 g of beans. The repellency test, all concentrations of the essential oil of A. conyzoides had neutral effect on the dry rot. Thus, it is concluded that the essential oil of mentrasto presents with fumigant effect and contact action for C. maculatus.