The term used here is a plural form of the word for Astarte, the goddess of love and war, which was worshipped in Canaan alongside Baal. Ashtaroth represented the female power of nature and was the goddess of fertility.
1 Like Baal, she is referred to in both the singular and plural. The appeal to her and the Baals had to do with their association with the fertility of the land and livestock, essential things for successful farming.
13 They abandoned the LORD and served the Baals and the Ashtaroth.