Annual and polyetic progression of citrus canker on trees protected with copper sprays

Abstract

The effects of copper sprays on annual and polyetic progress of citrus canker, caused by Xanthomonas citri subsp. citri, in the presence of the Asian citrus leafminer (Phyllocnistis citrella), were evaluated in a study conducted in a commercial orchard in northwest Paraná state, Brazil, where citrus canker is endemic. Nonlinear monomolecular, logistic and Gompertz models were fitted to monthly disease incidence data (proportion of leaves with symptoms) for each treatment for three seasons. The logistic model provided the best estimate of disease progress for all years and treatments evaluated and logistic parameter estimates were used to describe polyetic disease dynamics. Although citrus canker incidence increased during each of the seasons studied, it decreased over the whole study period, more so in copper-treated trees than in water-sprayed controls. Copper treatment reduced disease incidence compared with controls in every year, especially 2004-2005, when incidence was ca. 10-fold higher in controls than in treated plots (estimated asymptote values 0AE82 and 0AE07, respectively). Copper treatment also reduced estimated initial disease incidence and epidemic growth rates every year.

Copper resistance genes from different xanthomonads and citrus epiphytic bacteria confer resistance to Xanthomonas citri subsp. citri

“…citri (Xcc), causal agent of citrus canker (Behlau et al 2010a;Gottwald and Timmer 1995). Copper protects only where it is present on the plant surface and is not translocated across the plant surface nor does it readily move systemically.…”

Asymmetric chromosome segregation in Xanthomonas citri ssp. citri

“…These methods, collectively known as the disease management approach, include distinct cultivation strategies, the use of chemical formulations to contain the spread of Xac, and the plantation of citrus genotypes displaying relative resistance to citrus canker. The disease management approach is therefore intended to minimize and/or prevent damages and losses promoted by citrus canker, such as blemish on fruits, symptomatic fruit drop, defoliation, and stem dieback (Behlau et al 2010).…”

A comprehensive analysis of the Asiatic citrus canker eradication programme in São Paulo state, Brazil, from 1999 to 2009

“…Xcc infects preferably young expanding plant tissue (Gottwald & Graham, ). Thus, newly planted trees are more susceptible because leaf flushing is more frequent and represents a higher proportion of the canopy volume than for older trees, as observed previously (Leite & Mohan, ; Behlau et al ., ). Moreover, the CLM feeds on young leaf tissues and, therefore, contributes to increased Xcc infection in young groves (Belasque et al ., ; Jesus et al ., ; Christiano et al ., ; Hall et al ., ).…”