Spray Volume and Rate Based on the Tree Row Volume for a Sustainable Use of Copper in the Control of Citrus Canker

Abstract

Copper is the most efficient pesticide for the control of citrus canker (Xanthomonas citri subsp. citri). To mitigate the environmental impacts and costs, the copper sprays in citrus orchards are being optimized based on the tree-row-volume (TRV). A previous investigation allowed for significant reductions of the spray volume and copper rates. Nevertheless, the results also indicated the need for additional studies. The aim of this work was to assess whether both the spray volume and the metallic copper rate based on the TRV may be further reduced. A field trial was carried out during two seasons in a three-year-old commercial orchard of Pera sweet orange located in the municipality of Paranavaí, Paraná, Brazil. The volumes of 20 and 40 mL of spray mixture/m3 of the tree canopy were assessed in combination with the metallic copper rates of 10.5, 21.0, 36.8 or 52.5 mg/m3. Disease was measured as the temporal progress of canker incidence on leaves, cumulative dropped fruit with canker, and incidence of diseased fruit at harvest. The quality of sprays was assessed by measuring the copper deposition and leaf coverage. The treatment with the highest citrus canker control for the lowest use of water and copper was the combination of 40 mL and 36.8 mg/m3. Regression analyses indicated that the minimum threshold deposition of copper was ~1.5 µg Cu2+/cm2 leaf area. In addition, the lowest spray volume and copper rate necessary to achieve this deposition are 35 mL/m3 and 30 mg/m3. The use of 20 mL/m3 did not efficiently control the disease due to the deficient coverage of treated surfaces. This study demonstrated that is possible to use even lower amounts of copper and water without interfering with efficiency of control of citrus canker.

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“…In modern agriculture, synthetic chemical fungicides no doubt provide protection against fungal pathogens [9][10][11]. Due to the impact of chemical fungicides on environ-mental and human health, natural compounds and other alternatives (e.g., horticultural practices) have recently been implemented in integrated disease management (IDM) strategies [12][13][14][15].…”

Impact of diseases and pests on premature fruit drop in sweet orange orchards in São Paulo state citrus belt, Brazil

“…Management of citrus canker may be performed mainly by installing arboreal windbreaks, controlling the citrus leafminer and spraying copper-based bactericides. [60][61][62][63][64][65][66][67][68] The experience of other citrus-growing areas 60,69 associated with the optimization of the control measures, particularly the copper sprays, 32,65,66,68,70 is allowing for an efficient and more environmentally and economically sustainable control of citrus canker. The impact of this disease to the production in the citrus belt in the future will rely mainly on the favorability of the weather, i.e.…”

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“…In this sense, the tree row volume (TRV) methodology has indicated a reduction in the use of copper-based bactericides. First proposed by Byers et al (1971), TRV aims to optimize the spray volume and the copper rate based on the estimated canopy volume in a given area (Behlau et al, 2021b). In previous studies by Scapin et al (2015), the TRV method used in the citrus canker control showed a reduction in the water volume of 73% and a reduction in the copper rate by 50% compared to a standard rate.…”