Bioatividade da cera industrial de lima-ácida (Citrus latifolia Tanaka) sobre Cryptotermes brevis Walker

Abstract

industrial lime wax for control of drywood termite Cryptotermes brevis was evaluated. This termite was introduced into the Brazilian ecosystem and causes serious economical damage to the Historical, Artistic and Cultural Patrimony and general property. The mortality, anti-feeding effect, and activity towards the intestinal symbiont genus Foaina parameters were evaluated. The wax compounds, in both volatile and non-volatile fractions, were identified, and its bioactivity was determined. All bioassays were conducted using Pinus sp. wood blocks as substrate, which were treated with wax and its fractions. The wax bioassays showed high mortality levels in concentrations of 50, 75 and 100 mg/cm3, median lethal concentration (LC50) was 32,76 mg/cm3 and media lethal time (LT50) was 38 days. After 6 months, the anti-feeding action was persistent. The non-volatile fraction treatment showed an effective concentration for 50% feeding reduction (EC50) of 11,68 mg/cm3 (AI³50). Fractions 2, 3 and 4, obtained through VLC and GC-MS analyzed, presented high similar chemical composition, although presenting distinct 7-methoxycoumarin, 5,7-dimethoxycoumarin, 5-methoxypsoralen and 5,8-dimethoxypsoralen proportions. Significant anti-feeding values were obtained using wax and fraction 4, presenting EC50 of 24,69 and 21,91 mg/cm3, respectively. The total number of the symbionts genus Foaina present in the termites intestine was significantly reduced in the wax treatments. The results presented in the current work suggest that the lime wax, a citric industry residue, has potential for protecting wood against C. brevis.