It is a 1976 film about Killer Worms in Georgia, made in Georgia, distributed by American International Pictures.
And it has a theme sung by a London choirboy, and edited by Jose Larraz-partner Brian Smedley Aston (also behind Hardcore, with Fiona Redmond, giving his name alongside director James Kenelm Clarke to Ronald Fraser's sub-Paul Raymond character in that film, Marty Kenelm-Smedley).
Its' end theme is a maudlin ballad sung by an unknown British female singer which suits the film perfectly. I miss horror films that do that, end films with a soothing end theme. Contrast Piranha (1978) with its lovely Pino Donaggio end theme to the hard rock head-banging nausea festival of Piranha 3-D.
Apparently, Kim Basinger auditioned for the role of Geri, the female lead, but director Jeff Lieberman (who did the interesting "what do hippies fear most - baldness" film Blue Sunshine in 1978 and the 1981 backwoods slasher Just Before Dawn with George Kennedy) felt rightly she didn't like the sort of girl who grew up in a town with a worm farm. She might have lent some retroactive marquee value (as would Sylvester Stallone and Martin Sheen, also up for the roles of Mick and Roger, the latter of whom played by RA Dow in his only film role, covered in worms, and Mick is Don Scardino, also in Cruising (1980, as the nice gay) and in the 1980 slasher He Knows You're Alone, before becoming an Emmy-nominated TV director) but actress Patricia Pearcy is believable as the heroine.
There's a lovely Arrow Blu-ray which I urge you to get.
And I forgot to mention the effects are by a 24-year-old Rick Baker, still honing his craft, alongside tons of real worms, apparently a rare sub-breed were wiped out due to overuse in this film.
And Look at this poster art! Isn't it brillant? They don't make it like this anymore.