Remember that this is a temporary problem, unique to our beautiful Minnesota summers. One suggestion which has worked well thus far, has been to line the organics cart with a lawn and leaf bag. Then deposit the bagged organics into the lawn and leaf bag, and close that inside the cart. This works especially well if the green compostable bags are used in conjunction with the lawn and leaf bags. The idea is to create a physical barrier between the material and the flies.
From the City of Minneapolis website: “Maggots are a common, naturally occurring problem with many organics recycling programs. Even if you didn’t see them, maggots were commonly found in garbage carts before the City implemented the organics recycling program. Maggots are fly larvae and occur when flies lay eggs on organic materials. Maggots are more common in warmer temperatures. To prevent maggots inside your organics recycling cart, you must prevent mature flies from laying eggs in on your food scraps by eliminating odors and reducing their access to organic materials. A physical barrier works best.
If you find them in your cart, try leaving the lid open for a couple of hours, the City of Minneapolis recommends. Maggots will crawl to the top of the cart and often be eaten by birds.