Today I came across two unopened reed tubes which I had forgotten in the refrigerator so the cocoons had not hatched out. The image below shows why it is important to clean your tubes out in the winter and not leave them until late spring.
If people leave mason bee homes out unattended from year to year, the parasite population expands . They wouldn’t be so successful in the wild where mason bee nests are more dispersed in holes in wood or under tree bark. . When we provide homes for them however, along with increasing the bee population, we are also multiplying the success of the parasites. So if we are going to encourage bee populations, it is our responsibility to attend to the cocoons in the fall or winter to be sure they are not contaminated with a new generation of mites.
Occasionally I will take a sample of several dozen cocoons that are in cold storage and test them for viability. The longer they remain in storage before release, the more likely that some parasites will get a better head start.
Once the temperatures are up on sunny days, cocoons placed out near their prospective homes will start cutting their way out of the cocoons and fly off to get materials to fill their own tubes for the coming year. If there are remaining cocoons unopened after a week and a half of warm weather, then it may be worthwhile to check them for parasites. You can open a cocoon with a sharp box-cutter blade, carefully picking away at the tough cocoon. If the bees are healthy they will leave within a few minutes. You may encounter the following parasites and if so you should get rid of them. I have included some here that I not quite sure about as well. These parasites are natural, but when, as with many monocultures we concentrate many of one species together, the chance of pests finding a good place to thrive is increased.
The natural time for mason bee adults to emerge from the cocoons is normally quite early, in February or March in the lower part of Vancouver Island. This year I decided to hold some dormant in the refrigerator for a longer time to see if they would still hatch out successfully. By early June some of the bees were actually emerging and remaining very still in their jars in the refrigerator.
As soon as jar was removed from the fridge, once they they heated up they would fly off. (Note: as of June 25 they are still very active around the nest boxes.)
After a week of leaving the cocoons, I isolated the unhatched ones in a sealed jar, and sure enough in a few days the parasitic wasps were on the inside of the container.
Eaach time i had made a release of cocoons throughout the spring, I waited for at least a week and if they dint hatch, I openeeed them with a razor bled and released any live bees. about one in 30 unhatched cocoons would have parasitic larvae, so it could be that they are programmed to emerge more than a week after the regular bees emerge, in that way they would have active cocoon building so they could immediately begin lasying eggs in the cocoons. ??
This week I took out a few more mason bee which had already emerged from their cocoons while still in the containers in the refrigerator. They sit very dormant when cold but take only minutes to get active as they warm up. Their normal time of emergence from dormancy would be much earlier in the year but releasing them now ensures pollination of the late blooming fruits.
It was time to add a few more bees to the population outside since the strawberries continue to bloom and the kiwi fruit have started to bloom with this very warm weather we are having.
I also went around to all my mason bee boxes and removed the few cocoons that had not already hatched.
They either contained a dead bee or the larvae of the Monodontomerus, or “mono” which is a parasitic wasp that lays its eggs on the larva, usually within the cocoon of the mason bee. The tiny adult wasps emerged from one such cocoon. You can see the long penetrating ovipositer on the tail end. These have to be destroyed before they get to the bee larvae in the new cocoons.
Each year I find some branches of the younger Garry Oak trees that I have planted on the farm to have these small brown pillbox-like galls of an insect parasite . Usually the branch will die in the following year. I am attempting to get it identified. Also the branches of the trees these are found on often have deep scratches as if a bird was trying to get under the bark?? I think that leads to the weakening of the branch. I have saved one top leader of a Garry Oak tree like this by coating the damaged section with grafting paste.
Margot Moser of Nanoose bay, suggested that these galls are likely made by the Honey gall wasp Disholcaspis eldoradensis.A light colored, cylindrical (1⁄4 inch in diameter), flat-topped gall caused by a cynipid gall wasp.
I am not so sure and a look at the reference on California Oak Galls by Joyce Gross made me think it may even be Disholcaspis chrysolepidis
Phylum Arthropoda – Arthropods
Subphylum Hexapoda – Hexapods
Class Insecta – Insects
Order Hymenoptera – Ants, Bees, Wasps and Sawflies
Family Cynipidae – Gall Wasps
Species ?? Gall Wasp
I find that if I remove a set of Mason Bees from the refrigerator and put them out by the colonies to emerge from their cocoons as the weather warms up, if they are not hatched within a week, and yet look like viable cocoons, you can suspect that they may have Monodontomeruswasp parasites,
I opened several cocoons today and the results are shown below. In many of the cocoons the bee was still alive, but must be weakened so that they can’t chew their way out. If I got them soon enough before they were being thoroughly eaten, often with small white eggs attached to the outside which the bee brushes off easily, they can fly away after a few minutes. In the handful of about 100 cocoons that I looked through today, less than 5 % seem to be affected like this.