How to Disable logstash error logging in syslog

All Logstash errors logs in /var/log/logstash/* , but all the error logs of Logstash logs in /var/log/syslog too. Is there any way to disable logging errors of Logstash in /var/log/syslog?

logstash logs to /var/log/logstash and stdout. If your service manager cc's stdout to /var/log/syslog you should reconfigure your service manager.