CLEANING THE PHRAGMITES TUBES.
Any time from September on it is safe to open the Phragmites tubes to collect the mason bee cocoons inside. The earlier you do this the better as it prevents further development of pollen mites. Below are some photos from this years crop.
The ideal tube that you want to find will look like this
Occasionally I come across large white larvae in the tubes. These are not parasites, they are pollinator wasp species. See this post for photos of the wasps
PARASITES of MASON BEES
Pollen Mites
With a hand lens or as above, a closeup view on a cellphone you can see this mass of mites on the move. When I come across a tube with these mites, I segregate all other cocoons from the tube, and give them a thorough wash and cleaning before storing them in the refrigerator. I am also careful not to sell any of the cocoons from that batch. Mason bee houses that are not cleaned will have a build up of mite infestation so bad that eventually very few bees will be produced.
MONO WASPS:
I didn’t have many of these Chalcid wasps ( Monodontomerus) this year, I have done a previous post showing these in detail. These are “bodysnatchers” as they lay eggs on developing larvae which then eat the larvae
Mummification:
This is similar to a fungal infection called chalkbrood in honeybees.
UNKNOWN?
Other entries on this website about parasites and Problems with Mason Bee Culturing can be found here
Crownbees.com also has an excellent article on parasites of mason bees.