No abstract

Essential oils are widely recognized as an efficient and safe alternative for controlling pests in foods. However, a few studies have determined the persistence of these compounds in stored grains. The present study optimized and validated a fast and effective method for extraction and quantification of allyl isothiocyanate (AITC—the main component of mustard essential oil) residue in cowpea beans. It also investigated the persistence of this substance in the grains. The proposed method employs headspace solid-phase microextraction (HS-SPME) and gas chromatography with a flame ionization detector (GC/FID). For optimizing it, a central composite design (CCD) was used, where the best conditions for the extraction of the AITC were achieved using 15 min fiber exposure at 30 °C. The performance of the method was assessed by studying selectivity, linearity, limits of detection (LOD) and quantification (LOQ), precision, and accuracy. The LOD and LOQ for AITC were 0.11 and 0.33 μg kg –1 , respectively. The determination coefficient ( R 2 ) was above 0.99. The relative recovery rate ranged from 108.2 to 114.8%, with an interday coefficient of variation below 9%. After 36 h, no residue was detected in the samples, demonstrating that the AITC has low persistence and can be safely used as a bioinsecticide for grains.

Devido às influências, muitas vezes prejudiciais, que estresses abióticos exercem sobre a cultura da cenoura, faz-se necessário o uso de tecnologias ou produtos que minimizem tais efeitos. Entre as tecnologias disponíveis, o uso de bioestimulantes, produtos capazes de atuar na tolerância à estresses bióticos e abióticos, e influenciar na produtividade e qualidade na colheita, torna-se uma possibilidade. Com isso, o objetivo deste estudo foi avaliar o efeito de bioestimulante à base de hormônios, sobre a produtividade e qualidade de duas cultivares de cenoura, em duas épocas de plantio. Os experimentos foram conduzidos em delineamento de blocos ao acaso, com quatro repetições, em esquema de parcelas subdivididas. Nas parcelas foram dispostas as cultivares (Nantes – recomendada para cultivo de inverno e Brasília – recomendada para cultivo de verão) e, nas subparcelas as doses de bioestimulante (0, 5, 10, 15 e 20 mL.L -1 de água destilada). As variáveis avaliadas foram: comprimento e diâmetro de raiz, massa de matéria fresca de raiz, massa de matéria seca de raiz, volume radicular, carotenoides totais com base em ꞵ-caroteno, teor de açúcar solúvel, pH, acidez titulável total de raízes e produção total. A análise conjunta dos experimentos foi realizada para elucidar o efeito da época de plantio combinada ao uso de bioestimulantes. Os resultados sugerem efeito das doses de bioestimulante no comprimento de raiz. A dose que resultou em maior comprimento de raiz foi de 12,91 mL.L -1 para o plantio de verão. Para as demais variáveis não foi observado influência, exceto para sólidos solúveis que, reduziu linearmente com o aumento das doses do produto. A cultivar Brasília foi superior à cultivar Nantes para todas as características avaliadas, exceto para acidez titulável. O plantio de meia estação foi mais favorável para as variáveis massa de matéria fresca de raiz, produtividade, volume radicular e diâmetro de raiz, principalmente para a cultivar Brasília. Palavras-chave: Daucus carota. Bioestimulante. Regulador de crescimento.

The cowpea is subject to both quantitative and qualitative loss during storage due to attack by the insect pest Callosobruchus maculatus (Fabricius) (Coleoptera: Chrysomelidae). There is a growing interest in controlling the pest using insecticides that result from the reactions of secondary metabolites produced by plants, due to their high effi ciency, wide availability and selectivity for the target organisms. The present study aimed to evaluate the fumigant activity of allyl isothiocyanate (AITC) on the development of C. maculatus and its effect on the physical properties of the cowpea. To evaluate the instantaneous population growth rate (r i ), the insects were exposed to concentrations of 3.81, 5.71, 7.67, 9.41 and 17.85 mL AITC m -3 cowpea (corresponding to LC 1 , LC 10 , LC 30 , LC 50 and LC 95 ) for 40 days, after which the physical properties of the cowpea were analyzed. The degree of infestation increased considerably with the reduction in AITC concentration, as did the water content and electrical conductivity. The germination percentage and apparent density decreased with the reduction in AITC concentration. The LC 10 sublethal concentration reduced reproduction in C. maculatus and the degree of infestation of the cowpea after 40 days of storage. AITC inhibits the development of C. maculatus and helps maintain the physical properties of the cowpea, thereby representing an alternative to the use of traditional insecticides and showing potential for the control of insect pests in stored grain.