Adriano Augusto de Paiva Custódio

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.

Effect of Center-Pivot Irrigation in the Rust and Brown Eye Spot of Coffee

Incidence of rust (caused by Hemileia vastatrix) and brown eye spot (caused by Cercospora coffeicola) of coffee was evaluated for 2 years in southern Minas Gerais, Brazil, in a center-pivot-irrigated coffee crop with different water application levels. Treatments consisted of six water levels of 0 (nonirrigated), 60, 80, 100, 120, and 140% applied according to class A evaporation pan (CAE). Progress of disease was influenced significantly by different water levels; the highest incidence of rust occurred with lower water levels-0 (nonirrigated), 60, and 80% CAE-whereas the lowest incidence was detected with larger water levels: 120 and 140% CAE. There was one peak of rust incidence in August. The highest incidence of brown eye spot occurred with water levels of 100 and 140% CAE and the lowest incidence was found in the nonirrigated treatment. Two incidence peaks occurred in March and June. This study identified that irrigation methods and water levels can decisively affect the epidemiological behavior of diseases and, therefore, their management.