Cashew nut shell liquid and formulation: toxicity during the germination of lettuce, tomato seeds and coffee senna and seedling formation

Líquido da casca da castanha de caju e formulação: toxicidade sobre sementes de alface, tomate e fedegoso e formação de plântulas

ABSTRACT.

Cashew (Anacardium occidentale) nut shell liquid (CNSL) has been successfully used in trials as an Aedes aegypti larvicide, but little is known about its environmental effects. In this study, the potential effects of CNSL and a CNSL-based phyto-product formulation on the germination and growth of Lactuca sativa (lettuce), Lycopersicon esculentum (tomato) and Senna obtusifolia (coffee senna) were assessed. The pH of CNSL and the formulation were 6.4 and 6.8, respectively; the electrical conductivities were 2.89 μS cm^-1 (CNSL) and 2.21 μS cm^-1 (formulation), respectively, and both contained anacardic acid (53.2%) and degradation products. In bioassays for germination and growth, CNSL (25, 50, 100, 150, and 200 mg mL^-1), the formulation (100 mg mL^-1) and the control were used in a completely randomized design. The results demonstrated the chemical effects of CNSL, which negatively affected the germination and vigor of lettuce and tomato and the vigor of coffee senna; for growth, it negatively influenced both the root and aerial parts of lettuce and tomato, but only the roots of coffee senna. The formulation had negative effects on the vigor of coffee senna and the growth of tomato and lettuce seedlings (roots and aerial parts). The results indicate the phytotoxicity of CNSL and the formulation for the plant species tested.

Keywords:
Anacardiaceae; Anacardium occidentale; CNSL; anacardic acid, allelopathy