Parasitic wasp control
A comment on this blog asked for more pictures on candling cocoons.
Just today I candled 4000 cocoons. It seems like an awful lot, but when they are in petri dishes it is easy to do candle them- about 30 mins or so. I did see some duds that are of some interest. I call anything that is not a fully developed bee a ‘dud’. The percent ‘duds’ in this batch was 2.5%. Anything under 5% is excellent. But even with 107 duds there are some interesting ones. Few had fully developed parasitic wasps- ready to emerge in spring. Others were bee larvae that had not completed development into an adult. In the next day or so I will take some photos and put them on this blog.
I was teaching a group of people about candling the other day. It is a straight forward procedure but the conditions have to be right. The room that you do the candling in has to be completely dark- a bathroom without a window for example. Any extra light besides the flashlight is too much light and you cannot candle the cocoons.
This is the time when parasitic wasps can produce another generation every week. During the summer months, when temperatures are higher than in spring and fall, these pesky little critters come out of the nest and search for new mason bee cocoons to parasitize. I don’t know how, but these tiny adult wasps can make a tiny pin hole in the tube and crawl out and parasitize more bees.
Every July, when most bee eggs have turned into adult bees inside their cocoons, I gather all nests, set them under a veranda- where the ambient temperature is still warm. I place two Highrises per net-bag (see wasp proof bags on my web site beediverse.com). They sit stacked against the wall of my home until the end of September when harvesting takes place.
I find that net bags are successful and keep out wasp parasites. Percent parasitism is usually not more than 5%. If you have had trouble with these parasites, you will be pleasantly surprised with the outcome.