Compatibilidade de Beauveria sp. e Metarhizium sp. com óleo essencial da espécie vegetal Schinus molle L. e eficácia no controle de larvas de Aedes aegypti

Abstract

The present study evaluated the compatibility between the CG 206 of Beauveria sp. and CG 153 Metarhizium sp. Isolates associated with the essential oil of Schinus molle L. (aroeira-salsa) and its effectiveness in controlling A. aegypti larvae. For compatibility between fungi and oil, they were evaluated as colony forming units (CFU) and colony diameter evaluation. Fifty microliters of oil and non-oil suspensions (at concentration 75 and 25ppm) at 1.1 × 103 and 1.3 × 103 conidia mL-1, respectively, spread on five identified plates BDEL + chloramphenicol (0.5%) and incubated (25 ± 1 °C and RH≥80%). After seven days or number of colonies was quantified. To evaluate the colony diameter, ten microliters of oil-free and 25ppm oil suspension were inoculated into the center of Petri dishes containing BDEL + chloramphenicol (0.5%) and incubated (25o ± 1 °C and RH≥80%). Inoculum points were measured for 7 days. In the S. molle efficacy evaluation test, larvae (L2) were exposed to 22.5 mL of EO at ratings 25, 50, 75 and 100ppm and the control group was immersed in sterile chlorinated water +tween 80 where the survival rate was observed for seven days. In the biological assay with fungus and OE, Beauveria sp. CG 206 or Metarhizium sp. CG 153, grown in BDA, was suspended in sterile chlorinated water + tween 80 (0.01%) at a concentration of 1x107 conidial mL-1. For preparation of the oil-added fungal suspensions, each 10 ml fungal suspension received 0.0025% of the EO. Groups containing 15 larvae (N = 45) L2 were immersed in 22.5mL of suspensions. The control group was immersed in sterile chlorinated water + tween 80. A larval survival rate was evaluated daily for seven days. CFU tests and colony diameter were submitted to the Mann-Whitney test. Biological assays were submitted to nonparametric analysis (Kruskal-Wallis), followed by SNK test (Student-Newman-Keuls). Survival curve and survival averaging (S50) was performed using Kaplan-Meier. The significance level was 5% (P≤0.05). In CFU tests, 75 ppm and 25 ppm decreases the number of colonies formed; CFU percentages were 72.33% (CG 153 + 75ppm), 43.92% (CG 206 + 75ppm), 67.96% (CG 153 + 25ppm) and 27.55% (CG 206 + 25ppm). In the evaluation of colony growth, there was no difference between oil and non-oil suspensions of both isolates. In no efficacy test of S. molle EO, the oil was effective in the 50, 75 and 100 ppm tests and a 25 ppm was chosen to compose it as suspensions, for the largest percentage of larvae duration (88.26%). In biological assays, as described suspensions, the best results were observed in the treatments with CG 153 Metarhizium sp. 107 conidia mL-1 associated or not with oil, where the larvae S50 was 1 day. It is concluded that both fungi and essential oil are compatible and, although there is no adjuvant action, are good options for controlling A. aegypti larvae.