Approximately all disorders are answered on same site. Visit the Questions & Answers page & check specially Q G1 to G22.
http://www.carrotmuseum.co.uk/qna.htm
The direct link is not working but by following method you will find the file. Visit this page.
http://carrotmuseum.co.uk/sitemap.html. Go to the bottom of page and in category
Photos download PDF file by clicking on first link. The site is very interesting and informative about Carrots.