Bacterial halo blight
Disease symptoms, aetiology and dissemination
Pseudomonas syringae pv. garcae (Psgc), the causal agent of bacterial halo blight (BHB) of coffee, was first described in 1955 by Amaral et al. (1956) in the munici- pality of Garc a in the Brazilian state of S~ao Paulo.High increases in disease incidence have occurred after frost, for example after the 1973-1975 period in the state of Paran 
a (Kimura et al., 1973; Mohan, 1976), which
could be facilitated by the ice-nucleation activity exhib- ited by Psgc (Gonc alves & Massambani, 2011; Ara ujo et al., 2018).Bacterial halo blight has been reported in Kenya (Ramos & Shavdia, 1976), Ethiopia (Korobko & Wondinagegne, 1997), Uganda (Chen, 2002) and China (Chen, 2002; Bai et al., 2013).Although the disease was initially considered of minor importance, recurrent outbreaks have occurred in coffee plantations in several Brazilian states, mainly at higher altitudes (Kimura et al., 1973; Mohan, 1976; Cafepoint, 2011; Zoccoli et al., 2011; Rodrigues et al., 2013).Under severe infection, the disease can cause blackening of twigs and blighting of branch tips, resulting in dieback, defoliation, and apical meris- tem death, which in turn induces over-branching (Fig. 1a).