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

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

Report Date: 11/30/2016
Project: 15-050C   Year: 2016
Category: ACP Vector
Author: Franklin Behlau
Sponsor: Citrus Research and Development Foundation

The objective of this project was 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 crop loss. The experiment was 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 were the combination of up to three control measures (Cu, Wb, Lc) or none. The presence or absence of windbreak represented a plot. The presence or absence of copper sprays and leafminer control represented a subplot. Each subplot was composed of 112 trees. Each of the eight treatments had three replicates. Cu treated plots were sprayed with Kocide (35% metallic copper) at 1 kg metallic copper/ha every 21 days. Lc was performed with application of abamectin at 150 ml/ha every 21 days. Casuarina was used as a natural Wb around the plots. Disease evaluations started in December 2013 and included percentage of trees, leaves and fruits with ACC symptoms, and fruit yield. In the second season, the assessment of fruit drop was included. The present CRDF funding covered the period of November 2015 to October 2016, which corresponds to the second entire season assessed in the trial. The results observed during this season (2015-2016) followed the same trend of the previous one. Although the incidence of trees with citrus canker reached 100% for all treatments, the progression rate was lower in plots under complete management than trees with no management. The incidence of diseased trees in non-managed plots reached 100% in March 2015, 16 months after epidemics started, whereas, in managed plots this incidence was observed only a year later. Peaks of leaves with ACC symptoms in the last season for plots with complete management and no management were 2 and 42%, respectively. Fruit drop per tree due to canker was 109 and 18 for unmanaged and managed trees, respectively. These drops represented 37 and 5% of the crop loads, respectively. At harvest, incidence of fruit with ACC was 8 and 70% for managed trees and non-managed trees, respectively. Finally, average yield of trees treated with Cu+Wb+Lc was 84 kg, 83% higher than in trees under no management, which produced 46 kg. All measures reduced disease losses, but the combination of Cu and Wb provided the greatest disease control. Lc did not significantly contribute to reduce ACC incidence and disease impact on fruit loss.


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