Preparo do microencapsulado de Annona squamosa L. (Annonaceae) e toxicidade letal e subletal do microencapsulado a Tetranychus urticae (Koch, 1836) (Acari: Tetranychidae)

Abstract

The two-spotter mite, Tetranychus urticae (Koch, 1836) (Acari: Tetranychidae) is a pest that causes considerable losses in fruit, vegetables, ornamental and medicinal plants. The control with the use of botanical acaricides is a practice adopted since antiquity and was once again addressed. These products can cause lethal and sublethal effects to pests. However, they generally possess rapid degradation, which can be minimized by the preparation of microencapsulated formulations. The Annona squamosa L. (Annonaceae) is a plant that has substances in its composition with great acaricidal potential. The objective of this work was to prepare A. squamosa seeds of extracts, chemical characterization of A. squamosa of hexanic extract, lethal toxicity of T. urticae extracts, preparation and characterization of A. squamosa of microencapsulated, toxicity lethal microencapsulated of T. urticae and sublethal toxicity of hexanic extract and microencapsulated of T. urticae. The hexanic and ethanolic of the seed of A. squamosa extracts were prepared by cold extraction. Then, lethal concentrations were estimated by Probit analysis. The chemical characterization of the hexanic extract was performed through the extract partition and high performance liquid chromatography (HPLC) of the chloroform and hydrometanolic fractions. The preparation of the microencapsulated was performed by spray drying, using the hexanic extract and the polymers: starch, maltodextrin, gelatin and aerosil. Next, the characterization of the microencapsulated was performed through particle size analysis, scanning electron microscopy and thermogravimetric studies. The lethal concentrations of T. urticae microencapsulated were estimated by Probit analysis. The sublethal effects are evaluated through the ovicidal effect, repellent effect, instantaneous rate of population growth (ri) and residual effect. The hexanic extract had LC50 and LC99 estimated at 1.41 and 26.05 g/L, respectively. For the ethanolic extract, the estimated LC50 and LC99 were 2.08 and 53.27 g/L, respectively. The HPLC test showed a probable presence of acetogenins in the hexanic extract. The microencapsulated presented smooth microparticles, with no cracking, with little variation in size and four decomposition processes. The microencapsulated had LC50 and LC99 estimated at 5.37 and 45.26 g/L, respectively. The microencapsulated in LC99 was the treatment that had the lowest viability of eggs with 7.5 ± 2.70 % of viable eggs. The repellent effect for the hexanic extract occurred from LC95 and microencapsulated from LC50. The value of (ri) for both products decreased with increasing concentrations, however for LC95 of the microencapsulated the value was negative, indicating a decline in the population with a tendency to suppress mites. In the residual effect, it was observed that the microencapsulated in the LC99 was efficient until the 8th DAP with mortality of 61.2 ± 10.4 %. And the hexanic extract in the LC99 was efficient until the 15 th DAP with mortality of 61.2 ± 11.0 %, in the experiment conducted in greenhouse. For the field experiment 1, the microencapsulated in the LC99 was efficient until the 6th DAP with a mortality of 61.2 ± 8.1 %. And the hexanic extract in LC99 was efficient until the 7th DAP with mortality of 58.7 ± 10.3%. In the field experiment 2, hexanic extract in CL99 had efficiency up to 10th DAP, with 75.0 ± 6.0 % mortality and microencapsulation up to 9th DAP with 61.2 ± 6.1 % mortality. It is concluded that both the hexanic and microencapsulated extracts of A. squamosa are efficient in controlling T. urticae, which may cause lethal and sublethal toxicity. However, the microencapsulate has properties that may be favorable because it protects the active ingredient in the its core, reducing environmental and man-made contamination.