Blog's too big – how to split into parts

Hello, the home page of my site http://www.discodamaged.com is very slow to load. I got the following from my ISP when I asked if they could help me work out the slow loading speed –

I would note that your discodamaged.com WordPress install appears to have a potential coding issue as a query being made against its wp_posts table is regularly taking a very long time to complete, an example of the query in question is:

# Time: 140619 16:37:32
# User@Host: discodam_wp3[discodam_wp3] @ localhost []
# Query_time: 178.758675 Lock_time: 0.000143 Rows_sent: 10 Rows_examined: 235619
SET timestamp=1403192252;
SELECT SQL_CALC_FOUND_ROWS DISTINCT wp_posts.*, IF (wp_posts.post_type = ‘tribe_events’, wp_postmeta.meta_value, wp_posts.post_date) AS post_date, tribe_event_end_date.meta_value as EventEndDate FROM wp_posts LEFT JOIN wp_postmeta as wp_postmeta on wp_posts.ID = wp_postmeta.post_id AND wp_postmeta.meta_key = ‘_EventStartDate’ LEFT JOIN wp_postmeta as tribe_event_end_date ON ( wp_posts.ID = tribe_event_end_date.post_id AND tribe_event_end_date.meta_key = ‘_EventEndDate’ ) WHERE 1=1 AND wp_posts.post_type IN (‘post’, ‘tribe_events’) AND (wp_posts.post_status = ‘publish’) GROUP BY IF( wp_posts.post_parent = 0, wp_posts.ID, wp_posts.post_parent ) ORDER BY post_date DESC LIMIT 0, 10;

Various discussions on WordPress’ forums indicate slowdowns in this query are typically caused by a combination of a very large number of rows in the wp_posts table (your install currently has over 14,000 posts which as above equate to over 235,000 rows being checked when the above query is being performed) and faulty plugins, you may therefore wish to check these.

I have disabled plugins one by one, and none of them makes a difference, so I’m now trying to work out how to remove old posts to an archive. Is there a way to split my blog into several parts so that it doesn’t query the entire database each time?

Or can someone suggest an alternative solution to the slow home page loading (the other pages load fine, as does my other site which is hosted on the same server).