Chemical control of coffee leaf rust in Coffea canephora cv. conilon

The two species of coffee commercially harvested in Brazil and the world are Coffea arabica (Arabica coffee) and C. canephora (Conilon coffee). Coffee leaf rust, caused by Hemileia vastatrix, is the most frequent disease that affects coffee crops. However, damage has not been estimated, and the chemical control has not been determined for the Conilon coffee in Brazil. This study evaluated a new strategy to control coffee leaf rust through the application of triazole fungicides in soil and then to estimate the damage caused by the disease after treatment. To this end, an experiment was conducted in a randomized block design with eight treatments and four replications from November 2008 to May 2011. Every 30 days, leaves were collected from experimental plots to assess the disease incidence and severity. The coffee production was also evaluated between April and May each year. The disease progress curves were plotted with these data, and the area under the disease progress curve for the disease incidence and severity was calculated. The data of the incidence of disease and production were also used to estimate the damage caused by rust. The treatments with the applications in the soil were effective in controlling the disease; however, through the joint analysis of the disease's control and productivity, the best treatments were those that used ciproconazol or flutriafol in the soil, with or without foliar sprays treatments. There were no additional benefits with the foliar fungicides in Conilon coffee. The damage caused by rust in Conilon coffee can reach 47 % if measures are not implemented to the disease control.