Nematodes are a serious issue for coffee cultivation in Brazil. Because root infection by nematodes induces spectral variation in leaves and defines a unique spatial configuration in the cultivation field, the aim of this study was to use biophysical parameters and remote sensing data to discriminate and map healthy, moderately infected, and severely infected coffee plants. An experimental area in southern Minas Gerais State, in which the occurrence of nematodes was certified, was selected, and biophysical and spectral measurements of the leaves were made. Hyperspectral data were also used in a band simulation of the RapidEye sensor to identify the most sensitive spectral ranges for pathogen discrimination in coffee plants. These bands, plus a normalized difference vegetation index image, were used for a multispectral classification of healthy and nematode-infected areas. None of the biophysical parameters efficiently discriminated the leaves of healthy and infected plants, but the band simulation indicated that red, red edge, and near infrared spectral ranges were complementary to the discrimination of healthy coffee plants and the two levels of infection. The multispectral classification defined the spatial distribution of healthy, moderately infected, and severely infected coffee plants, with an overall accuracy of 78% and Kappa coefficient of 0.71. Consideringthe degree of uncertainty and high cost involved in conventional detection of soil parasites, thelevels of accuracy achieved were adequate.

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Bremia lactucae is recorded for the first time causing downy mildew on common sowthistle (Sonchus oleraceus) and spiny sowthistle (Sonchus asper) in Brazil. The disease and etiological agent are described. Pathogencity of sporangia obtained from S. oleraceus was tested on 12 species belonging to the Asteraceae, already recorded in the literature as hosts of B. lactucae, and four commonly cultivated varieties of lettuce. All four cultivars of lettuce, S. oleraceus and S. asper showed symptoms of the disease and sporulation of the pathogen 5 days after inoculation. It has been observed that the disease occurs on Sonchus spp. throughout the year in Vic¸osa (state of Minas Gerais), being more common on these two hosts than on lettuce. Both weeds are very common invaders of vegetable growing areas in Brazil. This indicates that those two hosts for the fungus may be important inoculum reservoirs for disease occurring in lettuce, highlighting the need for control of these weeds as part of the procedures aimed at controlling this disease. These results are also in agreement with the views that B. lactucae is split into host-specific infra-specific taxa. Lettuce and sowthistles are regarded as closely related, belonging to the same subfamily and tribe in the Asteraceae (Subfamily Cichorioideae: Tribe Lactuceae).www.blackwell-synergy.com

Stromatinia cepivora (= Sclerotium cepivorum), causal agent of the white rot, is a major soilborne pathogen that attacks garlic (Allium sativum L.), onion (Allium cepa L.), and other plants of the Alliacea family. The pathogen is difficult to control because it survives as sclerotia for decades in soil. White rot can cause total crop losses when sclerotia levels are high in soil and environmental conditions favorable for disease development. Aspects of the biology and epidemiology of S. cepivora have been investigated extensively worldwide. These studies have provided essential information to develop different control strategies. Currently, white rot management is based primarily on the application of fungicides and biocontrol agents to protect the crop against infection, and the use of natural and synthetic germination stimulants of sclerotia, soil fumigation and solarization to reduce sclerotia density in soils. In Brazil, few studies have been conducted to understand white rot epidemiology and effectiveness of control measures currently available, despite the disease being an economically important in garlic and onion production regions for many years. This review provides updated information on the biology of S. cepivora, and epidemiology and control of white rot to identify important knowledge gaps and future research directions for white rot in Brazil.

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Efficiency and compatibility of Trichoderma spp. and Bacillus spp. isolates on the inhibition of Sclerotium cepivorum Eficiência e compatibilidade de isolados de Trichoderma spp. e Bacillus spp. na inibição de Sclerotium cepivorum

Óleos essenciais de várias espécies de plantas possuem propriedades nematicidas e poderiam ser utilizados no controle do nematoide das galhas. Desta forma, esta pesquisa objetivou avaliar o efeito da aplicação de concentrações de eugenol no controle de Meloidogyne incognita e Meloidogyne javanica, em casa-de-vegetação. O eugenol foi aplicado nas concentrações de 0,25 mL L-1, 0,50 mL L-1, 0,75 mL L-1 e 1,00 mL L-1, na forma de pulverização foliar ou adição ao solo. O delineamento experimental foi inteiramente casualizado, em arranjo fatorial 4 x 2 + 1 (concentrações de eugenol x formas de aplicação + testemunha - tratamento adicional), com cinco repetições. Os números de galhas e de ovos de M. incognita e de ovos de M. javanica foram reduzidos em plantas tratadas com eugenol, em comparação com a testemunha. A adição ao solo foi o método mais eficiente de aplicação do eugenol, considerando-se a redução no número de galhas. Houve efeito significativo do aumento de concentrações de eugenol na redução do número de ovos de M. incognita. O eugenol apresenta potencial para ser utilizado no manejo do nematoide das galhas, embora novos estudos ainda sejam necessários para suportar tal expectativa.