Effect of windbreaks, copper bactericides and citrus leaf miner control on temporal and spatial progress of citrus canker

Effect of windbreaks, copper bactericides and citrus leaf miner control on temporal and spatial progress of citrus canker

Report Date: 01/14/2016
Project: 15-050C   Year: 2015
Category: Horticultural & Management
Author: Franklin Behlau
Sponsor: Citrus Research and Development Foundation

Background information The objective of this project is to quantify the relative effect of copper (Cu), windbreak (Wb) and leafminer control (Lc) on the spatial and temporal progress of Asiatic citrus canker (ACC) under conducive conditions for epidemics and disease loss. The experiment is set up in a 10 ha plot planted with Valencia sweet orange grafted on Rangpur lime located in the municipality of Xambre, Paran´┐Ż, Brazil. The different treatments are the combination of up to three control measures (Cu, Wb, Lc) or none. The presence or absence of windbreak represents a plot. The presence or absence of copper sprays and leafminer control represents a subplot. Each subplot is composed of 112 trees. Each of the eight treatments has three replicates. Cu treated plots are being sprayed with Kocide (35% metallic copper) at 1 kg metallic copper/ha every 21 days. Lc is being performed with application of abamectin at 150 ml/ha every 21 days. Casuarina is used as a natural Wb around the plots. Disease evaluations started in December 2013 and include percentage of ACC symptomatic trees, proportion of the canopy affected by the disease, incidence of symptomatic fruits at harvest, and yield. CRDF funding will cover the period of November 2015 to October 2016. Pre-funding progress results Nineteen months since the onset of the epidemics (July 2015), the incidences of diseased trees in the plots with complete management (Cu, Wb, Lc) and no management reached 45.2 and 97.6%, respectively. ACC diseased trees under complete management showed a minimal citrus canker severity of 0.8% as opposed to 31.4% observed on trees without any control. At first harvest, the incidences of symptomatic fruits from trees treated with the tree measures and none were 3.8 and 58.5%, respectively. Finally, production of trees in the first harvest revealed the same trend observed for other assessments. Fruit yield of trees under complete management (40 kg/tree) was 186% higher than control trees (14 kg/tree). The combination of Cu and Wb is showing the greatest importance for disease control. Post-funding progress results Trees continued to be assessed monthly as previously described. By the end of this report, disease assessments of December 2015 had been performed but not processed. The assessments of January 2016 had not been concluded. Thus, up to November 2015, disease has not progressed since July 2015 as conducive conditions for the pathogen in the trial started in December. In November 2015, the incidences of diseased trees in the plots with complete management and no management reached 43.8 and 97.9%, respectively. Severity of citrus canker in the canopy dropped for all treatments and reached 0.6 and 2.5%. The same trend was observed in the previous year and it was mainly due to drop of ACC-affected leaves, production of spring flushes and lack of favorable weather conditions for disease outbreaks, which are expected to occur in the upcoming months.


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