Avaliação do extrato aquoso de folhas de juazeiro associado a óleos vegetais adjuvantes como acaricida natural para o controle de Tetranychus ludeni

Abstract

The pest mite Tetranychus ludeni Zacher (Acari: Tetranychidae) causes irreversible damage to cotton (Gossypium hirsuntum L.), which has great socioeconomic importance as it is the main source of raw material for textile industries in Brazil and worldwide. Control of this pest is usually done with synthetic acaricides, which have generated resistance in populations of these arthropods, in addition to being unfeasible in terms of sustainability and environmental protection. In this context, the present study aimed to evaluate the effect of adding vegetable oils: coconut (1.5%), soybean (1.5%), canola (1.5%) and sunflower (1.5%), as adjuvants to the aqueous extract of the leaves of Sarcomphalus joazeiro Mart (Rhamnaceae), to be used as a natural acaricide to control the mite T. ludeni. The efficiency and mortality of the extract was estimated in the laboratory at concentrations that kill 50% (LC50) and 90% (LC90) of the population, [3.0%] and [8.81%] respectively, the repetitions were duplicated to analyze the effect in preventive and curative tests. A residual effect test was carried out in the field, where cotton seedlings were kept in cages lined with organza. The phytotoxicity test was evaluated by comparing it with the diagrammatic scale proposed by Martins et al. (2014). The presence of saponins, tannins and alkaloids was also identified through phytochemical tests in the extract. The aqueous extract of juazeiro leaves proved to be toxic against T. ludeni, its effect being enhanced with the use of vegetable oils as adjuvants. All the adjuvants tested were efficient in controlling T. ludeni causing mortality higher than 70%. The adjuvant oil that stood out the most was sunflower oil followed by coconut oil. The use of adjuvant oils associated with the extract of juazeiro did not cause phytotoxicity to cotton, probably due to its rapid degradation. Thus, it is a potential natural, biodegradable, low cost and effective acaricide against the mite T. ludeni.