Great question, and one many webmasters might be interested in since the Baidu spider is notoriously aggressive and can zap resources from servers...
As indicated in Baidu's Web Search news, the Baidu spider does not support the Crawl-delay notification setting, and instead requires you to register and verify your site with its Baidu Webmaster Tools platform, as stated here on its site.
This appears to be the only option to control the crawling frequency directly with Baidu.
The problem is that other spam bots use Baidu's user-agents (listed here under number 2) to spider your site, as indicated in their FAQ's here under number 4. So requesting a slower crawl rate with Baidu may not solve everything.
Therefore, if you do decide to use Baidu's Webmaster Tools, it might be wise to also compare its user-agents with IP's known to be associated with them by using a resource like the Bots vs Browsers Database, or using a reverse DNS lookup
The only other options are to either block all Baidu user-agents, and thus sacrifice potential traffic from Baidu, or attempt to limit excessive requests using something like mod_qos for Apache, which claims to manage:
- The maximum number of concurrent requests to a location/resource
(URL) or virtual host.
- Limitation of the bandwidth such as the maximum allowed number of requests per second to an URL or the maximum/minimum of downloaded kbytes per second.
- Limits the number of request events per second (special request conditions).
- It can also "detect" very important persons (VIP) which may access the web server without or with fewer restrictions.
- Generic request line and header filter to deny unauthorized operations. Request body data limitation and filtering (requires mod_parp).
- Limitations on the TCP connection level, e.g., the maximum number of allowed connections from a single IP source address or dynamic keep-alive control.
- Prefers known IP addresses when server runs out of free TCP connections.
I haven't found reported experiences with Baidu Webmaster Tools, which is slow to load and has translation issues (no English version either). That might be helpful, but opinion-based of course.