Inoculum reduction and vector control on the temporal progress of citrus variegated chlorosis incidence

Abstract

BACKGROUND: Citrus variegated chlorosis (CVC) is an important citrus disease caused by the sharpshooter-transmitted bacterium Xylella fastidiosa subsp. pauca. Information about the efficacy of its disease management is bounded to either inoculum reduction or vector control. This study aimed to assess the role of different frequencies of roguing of symptomatic trees combined with different chemical control programs for the sharpshooters on CVC temporal progress. The experimental area was set up in October 2005 and had a 3 × 3 factorial design. Symptomatic tree removal intervals were every 28, 56, and 112 days to May 2012. Vector control treatments were no control, program A (PA), and program B (PB). Contact insecticides were sprayed every 28 (PA) or 14 (PB) days. Trees within both programs were treated with systemic and foliar insecticides to October 2008. After this, systemic insecticides were discontinued and only foliar treatments were applied. The number of diseased trees and the sharpshooter population were assessed to April 2015. RESULTS: Detection of the first symptomatic trees was similar for all treatments and occurred, on average, in month 50 after planting. Sharpshooter population and cumulative disease incidence were similar for all roguing intervals and between vector control programs, differing in plots with no control. We observed a reduction over 85% in disease incidence for both PA and PB compared with no control.CONCLUSION: These results support systematic control of sharpshooters as an efficient strategy for reducing CVC progress.

Transmission and distribution of Xylella fastidiosa subsp. pauca in olive trees as a parameter for managing olive quick decline syndrome

“…Although published experiments have shown some positive effects of delivered molecules reducing symptom development and bacterial multiplication (Muranaka et al, 2013;Navarrete & De La Fuente, 2014;Scortichini et al, 2021), there is currently no control measure available to eliminate the bacteria from a diseased plant in open field conditions (Bragard et al, 2019;Kyrkou et al, 2018;Morelli et al, 2021). On the other hand, one example of successful management of disease caused by X. fastidiosa is for CVC (Coletta-Filho et al, 2020), where the main actions for control included the exclusion of the pathogen from propagative vegetative material, inoculum reduction in the field by uprooting diseased plants and/or pruning of branches with symptoms, plus the systematic control of vectors (Bassanezi et al, 2021;Gravena, 1998).…”

“…On the other hand, one example of successful management of disease caused by X . fastidiosa is for CVC (Coletta‐Filho et al, 2020), where the main actions for control included the exclusion of the pathogen from propagative vegetative material, inoculum reduction in the field by uprooting diseased plants and/or pruning of branches with symptoms, plus the systematic control of vectors (Bassanezi et al, 2021; Gravena, 1998).…”

“…Molecules such as N-acetyl-cysteine (NAC) have shown potential in reducing the severity of CVC in greenhouse experiments (Muranaka et al, 2013) but without bactericidal effect. Reduction of disease incidence (about 85%) was obtained with systematic chemical control of sharpshooters (Bassanezi et al, 2021), but this is a strategy with questionable sustainability. Pruning of branches with symptoms to eliminate X. fastidiosa from diseased plants as well as to minimize the spread of the disease was empirically used as a strategy to mitigate CVC (Gravena, 1998).…”

“…Similar results were also reported in X. fastidiosa-infected coffee plants (Queiroz-Voltan et al, 2006). The mitigation of grafted-and vector-transmissible diseases, such as the X. fastidiosa pathosystems, is complex and depends on integrated actions including the exclusion of the pathogen from the propagative material in the nursery, inoculum reduction measures, and plant protection for improved crop management in the field (Bassanezi et al, 2021;Johnson et al, 2021). In addition, the intriguing relations with landscape ecology, climatic conditions and host biology pose more challenges to managing X. fastidiosa-related diseases (Sicard et al, 2018).…”

“…Despite success in mitigating CVC in citrus orchards in Sao Paulo State, Brazil (Coletta-Filho et al, 2020), which was based on principles of exclusion, eradication and plant protection (Bassanezi et al, 2021), we only have incomplete information for OQDS. In addition, the transmission of X. fastidiosa during rooting of olive vegetative material has not been investigated.…”