Solarização do solo no controle da queima-da-saia em alface

Abstract

The bottom rot, caused by the fungus Rhizoctonia solani is an important lettuce disease in Brazil. This study aimed evaluate an alternative disease control, environmentally acceptable and cost effective. The study was conducted at the Horticultural Experimental Station Alejo von der Pahlen, located at kilometer 14 of the highway AM 10, Manaus, AM. Rizoctonia solani was isolated from lettuce plants showing disease symptoms and was caracterizated by the nuclei number and the anastomosis group to which it belongs. To evaluate the effect of soil solarization for 0, 14, 30 and 45 days, was used beds of 1 x 1 m and 20 cm highy containing soil and organic compound in a proportion of 8 L.m-2. The soil of the beds was infested with 300 g.m-2 of wheat colonized by R. solani. After infestation, the soil of the beds and was covered with polyethylene film 150 mm thick until finish the solarization period. After solarization, crisp lettuce seedlings (cv. Monica) with five leaves were transplanted to the beds. The experiment had a completely randomized design with four replications, and the experimental unit a construction with nine lettuce plants. Disease severity was assessed every three days. With the severity, data were developed the disease progress curves and calculated the areas under the disease progress curves. There was a significant reduction in disease severity of 67, 66 and 58% at 45, 30, and 15 solarization days, this result indicates the potential of solarization as a disease control alternative to lettuce. Solarization for 15 days was more advantageous for Amazonian farmers, allowing then to use the soil more quickly for cultivation with the same efficiency in disease control obtained in treatments with longer periods of solarization.