Copper rate and spray interval for joint management of citrus canker and citrus black spot in orange orchards

Citrus canker and citrus black spot are two of the most important diseases in the São Paulo (SP) citrus belt, Brazil. Canker control was based on an eradication program for six decades, but after a change in the legislation in 2017, the disease has been managed along with black spot. Although copper is a common pesticide for control of canker and black spot, spray setups have been established separately for each disease. The aim of this study was to determine copper rates and spray intervals for joint management of the two diseases. Two field trials (one for each disease) were conducted during two seasons. Control of canker or black spot was assessed with sprays at 14 or 21-day intervals using 10 to 63 mg metallic copper/m 3 tree canopy. Copper was also assessed for efficacy against black spot at 28-day spray intervals using 32 and 53 mg/m 3 . Copper treatments with 42 mg/m 3 every 21 days and 32 mg/m 3 every 14 days showed the best cost-benefit for canker control. These treatments reduced leaf canker incidence and fruit drop by up to 60%. Black spot symptoms and fruit drop were consistently reduced (by up to 90% and 60%, respectively) in both seasons by rates from 32 to 63 mg/m 3 and intervals of up to 28 days. Thus, the combination of 32 mg metallic copper/m 3 sprayed at 14 day intervals as well as 42 mg/m 3 every 21 days are the most cost-effective for joint management of citrus canker and black spot to be used in areas where both diseases are endemic and cause considerable yield losses.