Antônio Fernando de Souza

Effect of foliar application of potassium silicate on the progress of coffee leaf rust

In order to evaluate the effect of potassium silicate spray on the control of coffee leaf rust and coffee yield, an experiment was conducted during the 2005/2006 and 2006/2007 growing seasons on Coffea arabica cv. Catuai Vermelho IAC 144, in a location situated at an elevation of 850 m in Coimbra, Minas Gerais, Brazil. The treatments consisted of: 1 - potassium silicate; 2 - potassium silicate + copper hydroxide; 3 - copper hydroxide; 4 - epoxiconazole formulated with pyraclostrobin and 5 - control treatment. Six applications of potassium silicate and copper hydroxide were made twice per month from December to March of each year. Two applications of the systemic fungicide were done in December and March of each year. Potassium silicate alone or in combination with copper hydroxide was not efficient in reducing coffee leaf rust incidence and increasing yield under high incidence of coffee leaf rust.

Naupactus curtus (Coleoptera: Curculionidae) increasing the incidence of Ascochyta coffeae on Coffea arabica in Brazil

This is the first report of the weevil Naupactus curtus Boheman favouring Ascochyta disease on coffee plants in Brazil. From August to October 2008 (the period of N. curtus occurrence), six coffee crops were monitored with the evaluation of 565 coffee plants. Leaves showing injuries caused by N. curtus and Ascochyta coffeae strains were found in Ponte Nova and Jaboticatubas, Minas Gerais, Brazil. A positive and significant correlation between the number of lesions caused by the weevil and those resulting from an infection by the Ascochyta disease was observed. These results suggest that insect control may be an alternative in order to reduce disease proliferation.

Aplicação de silicato de potássio e crescimento foliar da cana-de-açúcar - DOI:10.5039/agraria.v6i1a902

Avaliou-se o efeito da aplicacao de doses crescentes de silicato de potassio sobre o crescimento foliar da cana-de-acucar em condicoes controladas. O experimento foi conduzido em delineamento inteiramente casualizado, com seis repeticoes e seis tratamentos constituidos por doses de silicato de potassio (0, 40, 80, 160, 200 e 240 g L -1 ). A aplicacao foliar de silicato de potassio influenciou de forma quadratica o crescimento foliar da cana-de-acucar. O maximo crescimento de area foliar e producao de materia seca das folhas foram obtidos com as doses de 66,6 e 40,0 g L -1 de silicato de potassio, respectivamente. Na dose de 51,0 g L -1 de silicato de potassio, obteve-se o maximo valor estimado da razao de area foliar. O teor de potassio (K) presente na materia seca da folha +1 respondeu de forma linear as doses de silicato de potassio. Entretanto, o elevado teor de K em funcao da aplicacao de altas doses de silicato de potassio reduziu o crescimento foliar da cana-de-acucar. Portanto, para a obtencao do maximo crescimento foliar da cana-de-acucar, a dose de silicato de potassio a ser aplicada deve estar compreendida entre 40,0 e 66,6 g L -1 .