BIOFUMIGANT AND REPELLENT ACTIVITY OF CITRONELLA ESSENTIAL OIL ON COWBEE BEANS (Atena Editora)

Abstract

The study aimed to evaluate the biofumigant and repellent action of citronella oil (Cymbopogon nardus) in a test with and without choice on cowpea weevil (Callosobruchus maculatus (Fabr.). In the no-choice experiment, concentrations 10 were used; 8.0; 6.0; 4.0; 2.0 and 0.0 µl/cm 3 and 4.0; 3.0; 2.0; 1.0 and 0.0 µl/cm 3 with a choice. In the first one, the concentrations were pipetted on the filter paper fixed on the inside of the lid of the polyethylene flasks, with 10g of cowpea cv BRS Guaribas added. Afterwards, ten non-sexed insects with 0 to 48h of age were added and taken to BOD for 96h. In the second, a circular arena formed by six flasks was used, the central container being symmetrically connected to the others by plastic tubes of 1cm in diameter and 10cm in length. 10g of cowpea grains cv BRS Guaribas were added to the peripheral flasks, the concentrations were added and mixed with the grains. Afterwards, 50 non-sexed C. maculatus insects aged between 0.0 and 48h were released into the central flasks of each arena, sealed with lids and taken to BOD for 24h. Then, the insects were removed from the treatments, counted to obtain the repellency index. The highest percentages of C. maculatus mortality were obtained with concentrations of 10µl; 8.0µl and 6.0µl and the efficiency of these same doses was respectively of 95.1%, 87.8% and 63.4%, while the total of eggs in any of the treatments with the oil varied from 11.2 to 23.0 and in the witness 112.2. The concentration of 10µl, in addition to causing the highest mortality of insects, provided 100% of the inviability of eggs. The essential oil of citronella (C. nardus) exerts efficient biofumigant activity on C. maculatus in stored cowpea grains, as well as all concentrations evaluated in the free-choice test have repellent action on C. maculatus.