Can you please help me ?
Thank you for contacting the Toronto Master Gardeners with your inquiry.
From one of our earlier posts: “Adult cherry fruit fly maggots emerge from the ground in late spring to early summer, about 5 weeks prior to cherry harvest. The female can lay up to 200 eggs. These hatch into larvae that tunnel into the cherry and when mature in 15-21 days burrow back out and drop to the ground. There they burrow into the soil to pupate. The pupa overwinters and develops into the adult fly the next year.”
The post entitled Worms in cherries gives step by step instruction as to the best defence against this pest.