Paulo Estevão de Souza

Avaliação da atividade fungitóxica de óleos essenciais de folhas de Eucalyptus sobre Fusarium oxysporum, Botrytis cinerea e Bipolaris sorokiniana

A maioria das plantas sao resistentes aos diferentes patogenos, e essa resistencia pode estar relacionada a existencia de compostos fungistaticos naturalmente produzidos. Com o presente trabalho, avaliou-se a atividade fungitoxica de oleos essenciais de eucaliptos. Os oleos foram obtidos de folhas dos eucaliptos mediante arraste a vapor de agua, utilizando o aparelho de Clevenger modificado. Nos ensaios biologicos, foram empregados os fitopatogenos Fusarium oxysporum, Botrytis cinerea e Bipolaris sorokiniana. O crescimento dos microorganismos na presenca de diferentes concentracoes de oleo (5, 50 e 500 mg/Kg), usando os meios de cultura BDA (Batata-Dextrose-Agar) e PCA (Batata-Cenoura-Agar), foi avaliado. Nas concentracoes de 500 mg/Kg dos oleos, foram observadas inibicoes significativas no crescimento micelial das especies fungicas, apos periodo de 7 dias. No entanto, o oleo essencial de Eucalyptus urophylla foi o que apresentou maior acao fungitoxica, que foi atribuida a presenca do composto denominado globulol, ausente no E.camaldulensis e no E. citriodora.

Incidência e severidade da cercosporiose do cafeeiro em função do suprimento de potássio e cálcio em solução nutritiva

An experiment was carried out at UFLA to evaluate the incidence and severity of the brown eye spot caused by Cercospora coffeicola in coffee (Coffea arabica) seedlings, in relation to different dosages of K and Ca in nutrient solution. The experimental design was completely randomized with 16 treatments, three replicates and two plants per replicate. Treatments were displayed in a 4 x 4 factorial scheme, with four levels of K (1, 3, 5 and 7 mmol/l) and four levels of Ca (2, 4, 6 and 8 mmol/l). The seedlings were inoculated, every week, for three months, with a conidial suspension of C. coffeicola of 15,000 conidia/ml. Total leaf area, total number of leaves and total injury number were obtained from seven evaluations made every fortnight. After the final evaluations, coffee seedlings were collected, the injured leaf area and the dry matter weight determined. The K x Ca interaction influenced total injury, total number of leaves and percentage of injured leaf area under the disease progress curve. The dosages of K reduced the total dry matter, the total leaf area and the area under the disease incidence progress curve, while the dosages of Ca influenced the total leaf area and the area under the disease incidence progress curve.

Intensidade da cercosporiose em mudas de cafeeiro em função de fontes e doses de silício

ABSTRACTEffect of silicon doses and sources on the intensity of the brown eye spot of coffee seedlings The objective of this work was to evaluate the effect of calcium and sodium silicate on the intensity of brown eyespot ( Cercospora coffeicola ) in coffee ( Coffea arabica ) seedlings (Catuai IAC 99) by using doses (0; 0.32; 0.63 and 1.26g of SiO 2 .kg -1 ) of substrate. Five evaluations were done by counting the number of diseased plants, number of leaves withlesions, number of lesions per leaf and total number of lesions per plant. The concentration of macro, micronutrients,silicon and lignin in the leaves was determined at the end of the experiment. The lowest area under the disease progresscurve of the total number of lesions was observed with 0.84 g.kg -1 of sodium silicate. Diseased plants were found to havea linear decrease of area under the disease progress curve and an increase in the concentration of lignin up to the dose of0.52 g.kg -1 of sodium silicate. The increase of sodium silicate and dose application into the soil up to 0.53 g.kg decreasedthe concentration of SiO

Comparison and validation of diagrammatic scales for brown eye spots in coffee tree leaves

Foi desenvolvida, comparada e avaliada com outras duas escalas uma escala diagramatica com seis niveis (0,1-3,0; 3,1-6,0; 6,1-12,0; 12,1-18,0; 18,1-30,0; 30,1-49,0%), para medir a severidade da cercosporiose em folhas de cafeeiro. A escala foi construida baseada em outras duas ja existentes, procurando aumentar a eficiencia da avaliacao e aproximar os valores estimados o mais proximo dos valores reais. Foram realizadas duas avaliacoes com a utilizacao de cada uma das tres escalas diagramaticas e uma avaliacao sem o seu auxilio, em intervalos de sete dias. Com o emprego da escala proposta, os avaliadores apresentaram melhores niveis de precisao, acuracia, reprodutibilidade e repetibilidade nas estimativas, quando comparados aos avaliadores que nao utilizaram a escala diagramatica, ou que utilizaram as escalas existentes. A escala diagramatica proposta demonstrou fornecer uma estimativa confiavel para avaliar a severidade da cercosporiose em folhas de cafeeiro.

IN VITRO ACTIVITY OF ESSENTIAL OILS OF Lippia sidoides AND Lippia gracilis AND THEIR MAJOR CHEMICAL COMPONENTS AGAINST Thielaviopsis paradoxa, CAUSAL AGENT OF STEM BLEEDING IN COCONUT PALMS

Essential oils of Lippia sidoides, Lippia gracilis and their main chemical components were investigated for in vitro control of Thielaviopsis paradoxa. Mycelial growth and a number of pathogen conidia were inhibited by the essential oil of L. sidoides at all concentrations tested (0.2; 0.5; 1.0; 3.0 μL mL-1). L. sidoides oil contained 42.33% thymol and 4.56% carvacrol, while L. gracilis oil contained 10% thymol and 41.7% carvacrol. Mycelial growth and conidial production of T. paradoxa were completely inhibited by thymol at a 0.3 μL m-1 concentration. The results suggest that thymol could potentially be used for controlling coconut stem bleeding.

Efeito do óleo essencial de pimenta longa (Piper hispidinervum C. DC) e do emulsificante Tween® 80 sobre o crescimento micelial de Alternaria alternata (Fungi: Hyphomycetes)

The object of this work was to evaluate the effectof essential oils from Long-pepper leaves Piper hispidinervum on the mycelial growth of Alternaria alternata and to analyze the influence of emulsifier Tween® 80 concentration in the control of this phytopathogen. The essential oil was obtained by steam stream distillation, using a modified Clevenger apparatus, and the chemical composition was analyzed by gas chromatography coupled to mass spectroscopy GC-MS and GC. For biological tests, the bioanalytical in vitro method was used, observing the growth or inhibition of such phytopathogen in BDA culture media, in the presence of different essential oil concentrations (0, 100, 250, 500, e 1000 mgL -1) under different Tween® 80 concentrations. Factorial scheme with four repetitions, in entirely randomized outline was adopted. The essential oil of Long-pepper inhibited the micellial growth of the A. alternata fungus at all of the concentrations tested. A 100% inhibition at the 1000 mgL -1 concentration was observed, and the percentage of emulsifier (Tween® 80) influenced the fungitoxic activity at the 250 mgL-1 and 500 mgL -1 concentrations of the essential oil.

Potencial fungitóxico do óleo essencial de Piper hispidinervum (pimenta longa) sobre os fungos fitopatogênicos Bipolaris sorokiniana, Fusarium oxysporum e Colletotrichum gloeosporioides

The objective of this study was to evaluate the in vitro antifungal activity of the essential oil of the leaves of Piper hispidinervum against Bipolaris sorokiniana, Fusarium oxysporum and Colletotrichum gloeosporioides. For the biological tests, using the bioanalitic test in vitro the concentrations of 100, 200, 500, 1000, 1500 and 2000 µg.mL-1 the essential oil. This were incorporated into PDA (potato dextrose agar) medium in order to evaluate fungal mycelial growth or inhibition. The statistic design used was completely randomized, with four replicates. In the concentration of 200 µg.mL-1, observed inhibited complete the phytopathogens Bipolaris sorokiniana while the Fusarium oxysporum and Colletotrichum gloeosporioides this is occurred in the concentration of 1000 µg.mL-1.

Progresso da cercosporiose (Cercospora coffeicola Berkeley & Cooke) em cafeeiros sob cultivos orgânico e convencional

The progress of brown eye spot in coffee trees in both organic and conventional crop systems was evaluated in two neighboring fields, in Santo Antonio do Amparo city, MG, between nov./2003 and nov./2005. The fields are under similar weather, soil and relief conditions and made up of ten-year-old coffee trees cv. Acaia MG-474-19. The incidence of brown eye spot was significantly higher in conventional system, whose average from two years demonstrated the area under the disease progress curve (3.905) higher than organic system (2.529). That was also demonstrated by the higher incidence on leaves (maximum 28% in 2004 and 29% in 2005) on conventional than on organic system (9% and 12%, respectively). The incidence on fruits was 18.2% in 2004 and 22% in 2005, while on organic system it was 11.5% and 15%, respectively. This higher susceptibility to disease on coffee trees in conventional system coincided with lower foliar content of calcium and magnesium for the fruit filling and fruit ripening stages compared with to the organic system. That was a consequence of higher production of the conventional system that resulted in yield 47.8% higher than organic one in 2004 (high number of berries). In 2005, the yield was similar in both crop systems but it was verified that the conventional production in 2005 was 64% lower than in 2004 whereas in the organic system from the difference in yield was 34%. This suggested for a tendency of lower effect of the disease in the following coffee harvest of the organic system compared to the conventional one.

Descrição da epidemia da ferrugem do cafeeiro com redes neuronais

The objective of this paper was to evaluate the potential of neural networks (NN) as an alternative method to the basic epidemiological approach to describe epidemics of coffee rust. The NN was developed from the intensities of coffee (Coffea arabica) rust along with the climatic variables collected in Lavras-MG between 13 February 1998 and 20 April 2001. The NN was built with climatic variables that were either selected in a stepwise regression analysis or by the Braincelâ system, software for NN building. Fifty-nine networks and 26 regression models were tested. The best models were selected based on small values of the mean square deviation (MSD) and of the mean prediction error (MPE). For the regression models, the highest coefficients of determination (R2) were used. The best model developed with neural networks had an MSD of 4.36 and an MPE of 2.43%. This model used the variables of minimum temperature, production, relative humidity of the air, and irradiance 30 days before the evaluation of disease. The best regression model was developed from 29 selected climatic variables in the network. The summary statistics for this model were: MPE=6.58%, MSE=4.36, and R2=0.80. The elaborated neural networks from a time series also were evaluated to describe the epidemic. The incidence of coffee rust at four previous fortnights resulted in a model with MPE=4.72% and an MSD=3.95.

Bioatividade de óleos essenciais no controle de Botrytis cinerea isolado de morangueiro

This study aimed evaluates essential oils in Botrytis cinerea isolates growth, which causes gray mould on strawberry. Were tested essential oils of lemon grass, palmrose, citronella, clove, cinnamon, mint, lavender, tangerine, eucalyptus, tea tree, rosemary and orange. The oils were analyzed in gas chromatograph attached to mass detector for identifying the mainly oils components. Were evaluated mycelial growth, conidia production and conidia germination of B. cinerea, with oil incorporation in culture medium. Were conducted an evaluation of oils volatile components and the efficiency of oils in fungicide-resistant isolate. For each test, different oils showed efficiency, however lemongrass, palmarosa, cinnamon and mint showed the best effects in all tests. All treatments demonstrated similar effects to recommended fungicide for the culture, which had methyl thiophanate. Two treatments (lemon grass and cinnamon oils), were effective against resistant isolate. Essential oils are shown as promising option for development of possible product for plant disease management.