Avaliação de óleos vegetais como adjuvantes para o aumento da eficiência do extrato de juazeiro sobre o ácaro tetranychus bastosi em pinhão-manso

Abstract

The mite Tetranychus bastosi Tuttle, Baker & Sales, 1977 (Tetranychidae) considered main pest of the physic nut culture Jatropha curcas L. (Euphorbiaceae) in some Brazilian Northeast states and its control is based on the use of synthetic acaricides, which are not registered for the crop and that may still cause the development of populations of the pest resistant to them, due to the indiscriminate use of these products. In this sense, the application of vegetal extracts is an alternative management measure, taking into account the composition of these products that contain substances with acaricidal potential. The objective of this work was to evaluate the effect of different adjuvants on the control efficiency of the aqueous extract of juazeiro leaves Ziziphus joazeiro Martius. (Rhamnaceae) on T. bastosi. In the laboratory, the toxicity of LC50 (11.87%) of the extract isolated (control) on the mite was evaluated, and in combination with the adjuvants: coconut oil (1.5%), canola oil (1.5%), and soy oil (1.5%). Leaf discs of physic nut were immersed for five seconds in one of the aforementioned treatments and kept in Petri dishes. Ten adult females were released on each disc. In order to evaluate the efficiency of the extract, physic nut leaves were infested with 20 adult T. bastosi females and 16 days after infestation pre-counting and spraying of the aforementioned treatments were performed. After 48 hours, 72 hours, 96 hours and 120 hours, the dead individuals were counted. In the evaluation of the residual effect the same plants were used, however the evaluation periods were 3h, 24h, 48h, 72h and 196h. Qualitative chemical analyzes were performed through tests for the detection of alkaloids, tannins and saponins. For all experiments, a completely randomized design was adopted. The results were submitted to analysis of variance and the means were compared by the Tukey test at the 5% level. The aqueous extract of Z. joazeiro leaves was toxic to the T. bastosi mite when tested alone or in combination with the adjuvant oils. The use of the adjuvant oils in combination with the extract did not significantly interfere in the mortality of T. bastosi in relation to the control. The adjuvants tested did not significantly contribute to the increase of the persistence of the extract in the leaves.The tannins and saponins were identified in the aqueous extract of juazeiro leaves, but it was not possible to observe the presence of alkaloids. Further studies with other concentrations are required to verify the efficiency of the extract with the adjuvants evaluated herein.