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/m3 of tree canopy were tested at the standard copper
rate of 0.525 g metallic copper/L. Additionally, 70 and 40 mL/m3 were also tested with copper rate
correction by leveling up the theoretical deposition of copper bactericide to that obtained with 100 mL/
m3.
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/m3 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.