We are having a tough year for our mason bees for some reason... I'd love any comments from the experts as to any causes or remedies for next year.
Last year we lost a lot of our cocoons to Mono wasps in early June (they even bored through the thick craft tubes). IIRC we ended up with about 60 or so cocoons after throwing most of them out (candled with a flash light to see the wasp larvae). This year I supplemented my remaining cocoons with an order of 20 and 30 cocoons from one of the well respected suppliers in order to build the population back up. We have 2 bee homes and my cocoons went in the top house and the 'replacement' cocoons went in the bottom.
Of my original cocoons most of them hatched but something is wiping them out in a hurry. All were placed out about 3-5 weeks ago and only 2 femalesremain. Last week there were 11. I found one dead on the ground, and another headless in the box. I haven't seen any birds around the boxes, and both our honeybee hives are thriving so far with no evidence of pesticide poisoning.
Even stranger, of the 'replacement cocoons' most never hatched. All were wintered together in my fridge in 2 separate boxes but the same environment.
I don't understand what happened this year and likely never will, but it's somewhat frustrating after doing everything by the book. Last year we had a fantastic year until the Mono hit. This year who knows? Maybe they had a poor pollen resource and ran out of fat reserves?
Here are a few photos. Note the queens that I cut out of the cocoons, one very dark and one very light.