RESUMO:Este trabalho teve como objetivo avaliar o efeito fungitóxico do óleo essencial de capim-citronela e do seu constituinte majoritário citronelal sobre a inibição micelial do fitopatógeno Fusarium subglutinans, agente causal da fusariose da cultura do abacaxi (Ananas comosus). Para avaliar o efeito do óleo essencial no crescimento micelial do fungo, foram utilizadas seis alíquotas (0, 5, 10, 15, 20 e 25 ìL) do óleo e do citronelal que foram distribuídas na superfície do meio BDA (batata-dextrose-ágar) antes da repicagem do fungo. O crescimento micelial foi medido após 48 h de instalação do experimento e em cinco épocas de avaliação (2, 4, 6, 8 e 10 dias após repicagem). Os resultados indicaram que o óleo essencial do capim-citronela demonstrou maior efeito inibitório do crescimento micelial do fungo F. subglutinans do que o composto citronelal. Em todas as alíquotas utilizadas o óleo essencial proporcionou menor taxa de crescimento micelial do que o citronelal. Palavras-chave: Cymbopogon nardus, planta medicinal, bioatividadeABSTRACT: Fungitoxic activity of essential oil of citronella grass (Cymbopogon nardus L.) and compound citronellal. This study aimed to evaluate the fungitoxic effect of the essential oil of citronella grass and its major constituent citronellal on the inhibition of mycelial pathogen Fusarium subglutinans, the causal agent of Fusarium culture of pineapple (Ananas comosus). To evaluate the effect of essential oil in the mycelial growth of the fungus were used six rates (0, 5, 10, 15, 20 and 25 mL) of oil that were distributed on the surface of PDA medium (potato dextrose agar) before subculturing of the fungus. Mycelial growth was measured after 48 h of the experiment and five times of assessment (2, 4, 6, 8 and 10 days after subculturing). The results indicated that the essential oil of citronella grass showed higher inhibitory effect of mycelial growth of the fungus F. subglutinans than compound citronellal. In all rates used of the essential oil gave lower growth rate than the mycelial citronellal.

The demand for effective insecticides in pest control with low toxicity to the nontarget organisms, such as natural enemies and pollinators, is increasing steadily. A good alternative for synthetic insecticides is natural compounds, including essential oils (EO). This work assessed toxicity of essential oils extracted from Artemisia annua, A. absinthium, A. camphorata, A. dracunculus and A. vulgaris against the melonworm Diaphania hyalinata (Linnaeus, 1758) (Lepidoptera: Crambidae) larvae, a pest of Cucurbitaceae, and their selectivity for fire ant Solenopsis saevissima (Smith) (Hymenoptera: Formicidae) and jataí bee Tetragonisca angustula (Latreille) (Meliponinae). The plants were grown in a greenhouse with mineral fertilization and were used for EO extraction. The insects in the bioassay belonged to the second instar of D. hyalinata and adult forms of S. saevissima and T. angustula. Essential oil from A. annua induced a high mortality rate in D. hyalinata (96 %) over a 48 h period. The same essential oil was selective for predator S. saevissima (42 % mortality) and pollinator T. angustula (74 % mortality), while causing high mortality in D. hyalinata. The insecticidal activity of A. annua oil was attributed to the synergism of its constituents viz., camphor and 1,8-cineole. Therefore, this essential oil contains constituents that are promising for effective use as insecticide due to its high toxicity and rapid action against D. hyalinata as well as low toxicity for predator and pollinator.

The rice blast is the most important disease of the rice, due to the damage that it causes in the productivity and grain quality. Aiming at the use of essential oils and plant extracts to control this disease. The objective of this study was to evaluate the curative and preventive effect of the extracts and essential oil of citronella grass (Cymbopogon nardus L.) to control rice blast. The evaluation of the curative effect was performed seven days after the spraying with the extracts of citronella grass. As for the evaluation of preventive effect, the plants were sprayed with the treatments and 24 hours after inoculated with 20 mL of the spore solution per tray. In the assessing of the curative effect, it was found that the application of fungicide and the diluted essential oil of citronella grass at a concentration of 2% plants showed no symptoms of blast in 50% of the repetitions. Regarding the evaluation of preventive effect, the plants showed no symptoms of the disease in concentrations of 1.5, 1.75 and 2% of the essential oil of citronella grass in 50% of the repetitions.

Artemisia absinthium, also known as wormwood, is used in traditional medicine as anti-parasitic and analgesic. The aim of the present study was to evaluate the effect of four doses of mineral fertilization in two harvest times on the content and composition of the essential oils produced by A. absinthium. The tested doses of mineral fertilization were the following: without fertilization (D0); 50% of the recommended dose (D1); recommended dose (D2); and 150% of the recommended dose (D3). The plants were cultivated in 10 L pots kept in greenhouse. The samples for extracting the essential oils were collected at 60 and 125 days after transplantation (DAT). The essential oils were obtained by hydrodistillation using a Clevenger-type apparatus. Identification and relative percentage of the compounds in the essential oils were performed by GC-MS. The essential oils content varied from 0.04% to 0.41% w/w. The highest essential oil content obtained was 0.41% using the dose D3 at 120 DAT. Myrcene and Z-isocitral were the major constituents of essential oils. According to the results obtained, A. absinthium can be used as a source of myrcene, depending on the dosage of mineral fertilization used and the time of harvest.