Duration of fungicide spray program for the control of citrus black spot in sweet orange based on cultivar maturation and orchard age

Abstract

Citrus black spot (CBS) damage and Phyllosticta citricarpa inoculum tend to increase in old orchards and in late-maturing cultivars of sweet orange. However, CBS control in São Paulo citrus belt is based on standard fungicide program of 180–220 days of fruit protection, regardless of cultivar and orchard age. This study aimed to investigate whether the protection period may be adjusted based on the cultivar maturation and age of orchards intended for juice processing. The efficacy of protection periods of 60, 100, 140, 180, 220 and 260 days was determined by assessing CBS incidence and severity and CBS-related fruit drop in 12 orchards over two seasons. The standard protection period, with 180 days targeted for mid-age and 220 days for old orchards, was the most cost effective for mid-season and late-maturing cultivars. These protection periods resulted in a significant reduction in CBS severity and fruit drop by up to ∼95% and ∼50%, respectively. For early-maturing cultivars, the duration of CBS spray program may be drastically reduced to 60 days for mid-age orchards and to 100 days for old orchards. These protection periods significantly reduced CBS severity and fruit drop by up to ∼92% and ∼50%, respectively. These adjustments in CBS fungicide protection period based on cultivar and orchard age may save up to US$14.3 million per season if adopted throughout the main Brazilian citrus belt. The results of this study allow citrus growers to save inputs, reduce costs, improve the operational efficiency within the farm and contribute to a more sustainable citrus industry.