Bioatividade de pós de espécies vegetais no manejo de Callosobruchus maculatus (Fabr., 1775) (Coleoptera: Chrysomelidae, Bruchinae), em grãos de feijão caupi (Vigna unguiculata)

Abstract

The Callosobruchus maculatus (Fabr., 1775) weevil (Coleoptera: Bruchinae) is one of the main pests of stored cowpea Vigna unguiculata (L.) Walp., (Fabaceae), which can cause significant economic losses. This insect’s control is usually done with chemicals that are not always effective in controlling pests or preventing reinfestation. An alternative method for the management of this insect is the use of plants with insecticidal properties. Thus, the objective of this work was to evaluate the insecticidal activity of Panax ginseng (Ginseng), Plectranchus barbatus (Falso boldo), Alternanthera brasiliana (Terramicina), Arnica montana (Arnica), Moringa oleifera (Moringa), Syzygium aromaticum (Carnation), Cinnamomum Zeylanicum (Canela), Eucalyptus urograndis (Eucalyptus) and Ageratum conyzoides (Mentrasto) in C. maculatus. A screening process was carried out with 1g of the nine plant species powder to determine the most promising plant, using glass containers carrying 20 grams of beans plus 1g of vegetable powder. Ten non-sexed adults of C. maculatus were released with 0-24 h of age. After 48 hours of confinement, the mortality percentages were determined. The contact action of the most efficient plant species estimated lethal and sublethal concentrations. For the repellency test, arenas containing three glass jars were used, with a central one interconnected to the others, containing at one edge of the container 10g of beans mixed with the amount of powder of each concentration, and at the other only 10g of beans (witness). Ten newly sexed adults of C. maculatus were released into the central pot. After 48 hours, the insects in each container were quantified to assess repellency, preference for oviposition, and emergency. The most promising plant was carnation, which showed high toxicity, killing 94% of the insects. For the contact test, the lethal concentration to kill 99% of the population (CL99) was 1.867g of powder for 20g of grains, and 95% (CL50) corresponded to 0.058g of powder for 20g of grains. In the repellency test, only the CL50 showed an attractive effect on the weevil. The lethal concentration (CL50) decreased the viability of eggs and the emergence of C. maculatus. Thus, it is concluded that carnation powder has a highly toxic effect on weevil.