Manejo da queima-das-folhas causada por Alternaria dauci em coentro

Abstract

Coriander is a vegetable belonging to the Apiacea family, widely consumed in Brazil. In the Northeast, it is largely produced by family farmers. However, factors such as the incidence of diseases can lead to a decline in production and economic losses to farmers. One of the main diseases that affect coriander is leaf blight caused by Alternaria dauci, which can damage the functioning of vital physiological processes in plants. Thus, the objective of this study is to evaluate the alternative and cultural control of the burning-of-leaves of coriander, using Bordeaux mixture, lime and ash mixture, garlic extract and Caetano melon extract for spraying the plants in two planting densities (2 g.m-1 and 4 g.m-1) and investigate the effect of treatments and disease on the physiological parameters of plants during the infectious process of Alternaria dauci. The incidence and percentage of disease intensity and physiological variables of chlorophyll fluorescence and gas exchange were evaluated. The experiments were conducted in the field, in a randomized block design with three replications, arranged in factorial scheme 4 (extracts and mistures) x 2 (densities) and in greenhouse, in a completely randomized design with 9 replications. Each experimental unit was composed of a pot containing two plants, both on the campus of the State University of Paraíba. The results showed that the ash and lime syrup, São Caetano melon extract and garlic extract did not decrease the incidence and severity of coriander burning. However, Bordeaux mixture reduces the intensity of coriander burning under natural infection conditions in the field and in a controlled environment with artificial inoculation. Cultural control, by cultivating a lower density of plants (2 g.m-1) reduces the incidence and severity when compared to the highest density of plants (4 g.m-1). In addition, the application of the solutions and extracts resulted in better efficiency in the use of water by the plants. The ash and lime solution showed the greatest increase in photosynthesis. The impact of the disease on photosynthesis of infected leaves was lower than the severity observed.