Soil application of acibenzolar-s-methyl and thiamethoxam for the management of citrus canker under subtropical conditio
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ORIGINAL ARTICLE
Soil application of acibenzolar-s-methyl and thiamethoxam for the management of citrus canker under subtropical conditions Flávia Elis de Mello 1
&
Camila Zaniboni 1 & Thales Barreto 1 & Michele R. L. da Silva 1 & Rui P. Leite Júnior 1
Received: 30 September 2019 / Revised: 29 April 2020 / Accepted: 5 May 2020 # Sociedade Brasileira de Fitopatologia 2020
Abstract Drench applications of systemic acquired resistance (SAR) inducing compounds acibenzolar-s-methyl (ASM) and thiamethoxam (THIA) may contribute for the control of citrus canker, caused by Xanthomonas citri subsp. citri. Here, we report the results of a 3-year field experiment on the effect of drench applications of two SAR-inducing compounds, applied alone or in combination with copper oxychloride (CuOX) foliar sprays, on citrus canker control, as well as tree growth and yield, of Natal sweet orange trees under Brazilian subtropical conditions. Leaf disease incidence, tree defoliation, and citrus leaf miner (Phyllocnistis citrella) attack were evaluated every 30 days for 16 months. Soil applications of ASM or THIA combined with foliar sprays of CuOX highly reduced citrus canker incidence on leaves. Effective control of the disease, comparable to regular foliar sprays of cupric bactericides, was obtained with two to four drench applications of SAR-inducing compounds. No differences among the treatments were observed in regard to tree height and canopy volume, and fruit yield of the young citrus trees. Soil applications of SAR-inducing compounds proved to be an important measure for the integrate management of citrus canker under the Brazilian subtropical conditions. Keywords Systemic acquired resistance . Xanthomonas citri subsp. citri . Citrus leaf miner . Copper in bacterial disease management . Neonicotinoid insecticide
Introduction Citrus canker caused by the gram-negative bacterium Xanthomonas citri subsp. citri (Xcc; syn. X. axonopodis pv. citri) is a serious disease for citrus production around the world. The pathogen infects the citrus trees causing necrotic and erumpent lesions on leaves, branches, and fruits (Gottwald et al. 2002). Severe infections can cause early defoliation, dieback, fruit drop, and consequently tree debilitation (Schubert et al. 2001). Xcc is disseminated by the combination of rainfall with blowing wind (Gottwald et al. 2001). In addition, the bacterium may also be disseminated at long distances through contaminated nursery trees and other propagative materials and diseased fruits (Gottwald et al. 2001). Natural openings, as stomata, or wounds caused mechanically or by insects, such as the citrus leaf miner (CLM)
* Flávia Elis de Mello [email protected] 1
Instituto Agronômico do Paraná, 86047-902 Londrina, Paraná, Brazil
(Phyllocnistis citrella Stainton), and thorns serve as an entrance site for the citrus canker bacterium in the plant tissue (Leite and Mohan 1990). Spray applications of copper compounds is one of the main components of the citrus canker integrated management (Leite and Mohan
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