Mason bees use mud to plug up their holes. They layer their nesting hole with mud, pollen, larva, mud, pollen, larva and make this layer 5-8 times in each hole to lay their babies and then they cap it off with mud. This means it is very important to not use any chemicals or pesticides in your soil when working in your garden.
In a previous blog post, we discussed ways to safely remove dandelions without using chemicals https://rentmasonbees.com/dandelions-bees-food-happiness/
Today, let’s talk about how to safely remove slugs without harming the precious soil our mason bees are using to build their nests.
1) NATURAL PREDATORS – Encourage natural predators to your yard to help eat the slugs. Birds, chickens, ducks, nematodes, frogs, salamanders, newts, toads, snakes, turtles, hedgehogs, shrews, ground beetles and rove beetles all love slugs. This is another reason to not use chemicals. Poisoning slugs will also poison these animals.
2) USE COMPANION PLANTS – By growing any of the following in companion with your plants you will protect them from slugs. Mint, Chives, Garlic, Geraniums, Foxgloves, Daffodils, Rosemary and Lavender.
3) BEER! – Yup, beer! The more stale the beer the better. Slugs love the aroma of yeast and will climb in and not be able to get back out. 
Bury a glass mason jar, tuna fish can or plastic yogurt cup in the soil. Keep the container 1 inch above ground to avoid catching slug-eating ground beetles. Fill half of it with beer and remove slugs and replace beer when needed.
4) COFFEE GROUNDS – You can use coffee grounds alone or mix with eggs shells to deter slugs.
5) SOOT AND ASH – The remains of fires are toxic to slugs. Spread around your plants to get rid of slugs naturally. Make sure you’re using ash from untreated wood, otherwise toxic substances may contaminate the ground. You’ll have to reapply after it rains.
6) SHARP EDGES – Slugs don’t like crossing over sharp objects. Sprinkle sand, gravel, crushed oyster shells (found in feed store for chickens), or pine needles around your plants. 
7) WOOL PELLETS – Similar to sharp edges, slugs don’t like the feel of wool. Look for wool pellets in your local garden store and sprinkle around your plants. When they get wet, they expand and slugs won’t cross over them.
8) NIGHT HUNT – Slugs come out at night, so grab some disposable gloves and go on a slug hunt with flashlights. This could be fun for the kids too. Catch and release in the forest or far away from your garden.
9) SLUG & SNAIL EGGS – Slugs lay about 40 eggs 6 times a year. 
If you spot any slug eggs in your garden you can remove them and dispose of them before they turn into more slugs. Here’s a picture of what slug eggs look like.
10) COPPER MESH OR TAPE– If you have a large area to cover or raised beds, you can spread copper mesh or tape around the base of your box or cut up and lay at the sides of your flower beds. Slugs do not like to touch copper. When their slime comes in contact with copper, it feels like a shock and they won’t go over it. You can buy copper mesh or self-adhesive copper tape online.
Do the bees need a clear area in the garden to harvest the soil? Will the space between plants be sufficient for their efforts?
They don’t need a specific area. They’ll find muddy soil for their nests.
My Slugs eat Daffodils..too the ground! IS Slugoo a chemical that hurts bees?
Thank you for asking. Slug bait will seep into the mud that mom mason bee uses for her nesting chambers. Here are 10 ways to safely remove slugs. https://rentmasonbees.com/10-ways-to-safely-remove-slugs-without-harming-mason-bees/
This was very helpful, thanks.