Tree-row-volume-based sprays of copper bactericide for control of citrus canker Marcelo da Silva Scapin a , Franklin Behlau a, * , Luis Henrique Mariano Scandelai a , Rafael Saraiva Fernandes a , Geraldo Jos  e Silva Junior a , Hamilton Humberto Ramos b a Fundo de Defesa da Citricultura e Fundecitrus, Departamento de Pesquisa e Desenvolvimento, Araraquara, S~ ao Paulo, Brazil b Instituto Agron^ omico e IAC, Centro de Engenharia e Automaç~ ao, Jundiaí, S~ ao Paulo, Brazil article info Article history: Received 19 March 2015 Received in revised form 6 July 2015 Accepted 7 July 2015 Available online 2 August 2015 Keywords: Xanthomonas citri subsp. citri Chemical control Tree volume Spray volume Citrus abstract Commonly, pre-determined copper spray volumes are indiscriminately applied to citrus orchards of different ages and sizes for control of citrus canker (Xanthomonas citri subsp. citri) leading to a waste of resources, such as water, energy, and chemicals. This study evaluated the effectiveness of copper applied following the tree-row-volume (TRV) methodology for control of citrus canker on sweet orange trees. Treatment design was based on the theoretical runoff volumes previously determined for the exterior and interior of a citrus tree. The volumes 150 (standard), 100 (internal runoff point), 70 (intermediate) and 40 mL (external runoff point) of spray mixture/m 3 of tree canopy were tested at the standard copper rate of 0.525 g metallic copper/L. Additionally, 70 and 40 mL/m 3 were also tested with copper rate correction by leveling up the theoretical deposition of copper bactericide to that obtained with 100 mL/ m 3 . Untreated control trees (UTC) were not sprayed with copper. Reduction of the spray volume did not affect disease control. While UTC trees presented a peak incidence of citrus canker on leaves of 30% in both years, copper-treated trees showed significantly lower peak incidences of 5e10%. Likewise, the average number of dropped fruits with citrus canker for the UTC was 2.0- to 1.5-fold higher than for copper treatments. At harvest, 30% of fruits from the UTC trees showed citrus canker symptoms. Conversely, only 3.3e9.8% of the fruits from the copper treatments were symptomatic. Moreover, using 40 mL/m 3 without adjusting the amount of metallic copper diminished disease control efficiency on leaves. Reduction of spray costs and water needs amounted to 40 and 73%, respectively. In addition to keeping effectiveness of disease control and being more environmentally friendly, the adaptation of the spray volumes and copper rates to the TRV may contribute to reducing production costs. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction Application of copper-based bactericides is the main measure for the chemical control of citrus canker (Xanthomonas citri subsp. citri) in regions where this disease is endemic. Sprays are usually performed in spring and summer when young and susceptible tree tissues develop, and the climatic conditions are favorable to the pathogen (Behlau et al., 2010; Gottwald et al., 2002; Leite and Mohan, 1990). These chemicals are intended to protect devel- oping sprouts and fruits, which have unprotected tissues due to continuous expansion (Albrigo et al., 1997; Timmer, 1988). There- fore, this disease is controlled following the first deposition of copper on leaves and fruits and then through the maintenance of this protective layer through frequent applications that are carried out while the tree tissue develops (Albrigo et al., 1997). The role of these bactericides is strictly preventive. They do not cure the disease or have any systemic activity in trees. Fixed or insoluble copper, such as copper hydroxide, copper oxychloride, or cuprous oxide are the most commonly used forms in sprays, which aim to form a film on tree tissues and from which copper ions are slowly released. The concentration of metal ions on the tree surface depends on the equilibrium between complexed and soluble forms of copper (Menkissoglu and Lindow, 1991). These characteristics reduce the risk of phytotoxicity and increase the residual activity of the pesticide (Menkissoglu and Lindow, 1991). The fixed copper * Corresponding author. Avenida Adhemar Pereira de Barros, 201, Araraquara, SP, Brazil. E-mail address: franklin@fundecitrus.com.br (F. Behlau). Contents lists available at ScienceDirect Crop Protection journal homepage: www.elsevier.com/locate/cropro http://dx.doi.org/10.1016/j.cropro.2015.07.007 0261-2194/© 2015 Elsevier Ltd. All rights reserved. Crop Protection 77 (2015) 119e126