Produtos alternativos na inibição de Sclerotinia sclerotiorum "in vitro"

O mofo-branco, causado por Sclerotinia sclerotiorum, é uma doença importante na cultura do tomateiro. O objetivo do trabalho foi avaliar o efeito de extratos de plantas, resíduos animais e subprodutos industriais no desenvolvimento micelial e na produção de escleródios do fungo "in vitro". Os tratamentos testados foram diferentes concentrações de licor pirolenhoso, óleo de nim, glutamato monossódico, biossólido e composto orgânico [(borra de café (50%) cinza de carvão (10%), resíduo de milho (25%), esterco de aves (12,5%) e farinha de aves (2,5%)], além de duas testemunhas, sem adição de produtos ao meio e com adição do fungicida procimidone. O fungo submetido aos diferentes tratamentos foi incubado à temperatura de 22ºC e luminosidade constante de 260 lux. Foram avaliadas o crescimento micelial, a produção de escleródios e a viabilidade dos mesmos aos 7 e 17 dias após a repicagem do fungo para meio de neon. O composto orgânico a 30 % mostrou-se eficiente na inibição do crescimento micelial e na produção de escleródios. Este tratamento, assim como o óleo de nim a 0,5%, foi analisado com relação à sua influência na microbiota no solo por meio de uma análise de respirometria, que indicou que ambos os tratamentos foram degradados rapidamente, não causando assim malefícios à mesma.The white mold, caused by Sclerotinia sclerotiorum, is a very important disease in tomato crops. The objective of this work was to study the effect of plant extracts, animal residues and industrial by-products extracts on the fungus in vitro growth. Treatments consisted of different concentrations of pyrolignous oil, neem oil, monosodium glutamate, sewage sludge and organic compost [coffee residue (50%) coal residue (10%), maize residue (25%), poultry waste (12.5%), poultry meal (2.5%)]. Positive control consisted of Petri dishes with PDA medium and negative control treatment consisted of PDA medium with procymidone. Fungus colonies were incubated at 22ºC and light intensity of 260 lux. Variables such as mycelium growth rate, sclerotia production, and viability 7 and 17 days after the transfer of mycelium disc to neon media were assessed. The extract of organic compost at 30% was effective in controlling mycelial growth and sclerotia production. This treatment, as well as neem oil at 0.5% increased soil respiration

Diagrammatic scale for assessment of Alternaria Brown Spot of citrus

Com o objetivo de padronizar as avaliações da severidade da Mancha Marrom de Alternaria, foi desenvolvida uma escala diagramática considerando a distribuição, a forma, a freqüência das lesões e os níveis mínimo e máximo de severidade encontrados em campo. Dois tipos de lesões comuns em campo foram representados na escala, pequenas de formato circular ou irregular (0,1; 1; 2,5; 5; 11 e 25 % da área do fruto lesionada) e grandes, nesse caso sempre circulares (1; 2,5; 5; 10 e 17 % da área do fruto lesionada). A validação da escala foi feita em duas etapas: na primeira, quatro avaliadores estimaram a severidade de 79 fotos de frutos sintomáticos, sem o uso da escala, e na segunda, os avaliadores estimaram a severidade dos mesmos frutos com o uso da escala. Quando a escala não foi utilizada, o r² estimado para todo o conjunto de dados foi 0,69, o intercepto (a) 1,42 e o coeficiente angular (b) 0,77. Com o uso da escala, esses parâmetros foram de 0,84, 1,59 e 0,84, respectivamente. A escala mostrou-se adequada para avaliações da severidade da Mancha Marrom de Alternaria em frutos cítricos.A diagrammatic scale of Alternaria Brown Spot in citrus was developed in order to standardize disease severity assessments. The scale was built taking into consideration the distribution, shape and frequency of lesions as well as minimum and maximum severity levels found in the field. Two types of symptoms widely observed at field were represented in the diagrammatic scale: small circular or irregular lesions (0.1 1 2.5 5 11 and 25%) and large circular lesions (1 2.5 5 10 and 17%). The validation of the scale was accomplished in two stages. Firstly, four experts estimated the severity of disease in 79 photographs of citrus fruits with symptoms without using the diagrammatic scale. Secondly, the experts estimated the severity of the disease on the same fruits, by using the scale. When the scale was not used, the coefficient of determination (r²) was 0.69, the intercept (a) 1.42 and the angular coefficient (b) 0.77, while by using the scale these parameters were 0.84, 1.59 and 0.84, respectively. The scale was shown to be appropriate for severity assessment of Alternaria Brown Spot on citrus fruits.Fundação de Amparo à pesquisa do Estado de São Paulo (FAPESP

Comparative analysis for quantification of Citrus Variegated Chlorosis in the field

Citrus Variegated Chlorosis (CVC) caused by Xylella fastidiosa is one of the most important diseases for Brazilian citriculture. The CVC is a vascular disease with a long incubation period and symptoms similar to other disorders, and this factors difficult the CVC quantification in the field. Two methods of CVC assessment were compared in this study. The first method was based on a descriptive rating scale with four ratings, commonly used for the disease quantification. The second one was based on the incidence of symptomatic branches. The quantification of CVC through these two methods was carried out in a 10-year-old 'Natal' sweet orange orchard. The descriptive scale considered the symptoms of the entire plant. The disease incidence was evaluated in 36 branches in each plant. The assessments were conducted by three raters in 144 plants in July 2006 and July 2007 as well as in March and November 2008. The descriptive scale did not allow an accurate assessment and resulted in a moderate strength of agreement among the raters. On the other hand, the incidence quantification of CVC through the symptomatic branches showed high repeatability among the raters. We suggest the use of incidence of symptomatic branches as variable for CVC quantification.(CNPq) The National Council for Scientific and Technological Developmen

Eradicant and curative treatments of hexanal against peach brown rot

Brown rot, caused by Monilinia spp. , is one of the most important peach (Prunuspersica (L.) Batsch) diseases and the main cause of postharvest losses. Currently, alternative methods for postharvest disease control, such as the use of volatiles, are under investigation. The objective of this study was to determine the effects of hexanal on the in vitro development of Monilinia fructicola and M. laxa and on monocyclic components of brown rot on peaches. To evaluate the effect on pathogen development in vitro, a single dose of 215 µL of liquid hexanal was placed on glass jars in closed plastic containers (4.3 L) at the moment of fungi transfer, 24 or 48 h after transferring to Petri dishes. After hexanal application, the Petri dishes were kept inside the containers that were closed for 24 h at 20 ºC. Mycelial growth was measured seven days after hexanal removal. For in vivo assays, inoculated fruits were kept in closed plastic containers, and hexanal was applied at the moment of fruit inoculation or 24 hours thereafter. The monocyclic components infection frequency, expressed as brown rot incidence, lesion diameter and lesion sporulation, were assessed daily for seven days. Overall, hexanal was more effective in inhibiting mycelial growth when applied at the moment of pathogen transfer. Hexanal did not prevent pathogen infection, but reduced lesion diameter and completely inhibited spore production on the fruit for both treatments. Hexanal provides a promising alternative for chemical control and can be used in postharvest handling systems

Alternative products in the "in vitro" inhibition of Sclerotinia sclerotiorum

The white mold, caused by Sclerotinia sclerotiorum, is a very important disease in tomato crops. The objective of this work was to study the effect of plant extracts, animal residues and industrial by-products extracts on the fungus in vitro growth. Treatments consisted of different concentrations of pyrolignous oil, neem oil, monosodium glutamate, sewage sludge and organic compost [coffee residue (50%) coal residue (10%), maize residue (25%), poultry waste (12.5%), poultry meal (2.5%)]. Positive control consisted of Petri dishes with PDA medium and negative control treatment consisted of PDA medium with procymidone. Fungus colonies were incubated at 22ºC and light intensity of 260 lux. Variables such as mycelium growth rate, sclerotia production, and viability 7 and 17 days after the transfer of mycelium disc to neon media were assessed. The extract of organic compost at 30% was effective in controlling mycelial growth and sclerotia production. This treatment, as well as neem oil at 0.5% increased soil respiration