There's a lot of anecdotal evidence about spiders being detered by conkers. It was, apparently, the subject of a lengthy thread on Answer Bank a few years ago. I found it when I googled for evidence of this as I had been thinking of asking the question about it here.
apparently you can buy a spray and its made of Chestnut Oil so that would support that they are repelled by the smell, think you have to pierce the conkers