Page 36 - ALG Issue 4 2018

Feature On
Winter care for Solitary Bees
Firstly, allow me to apologise to anyone who did not receive a fact sheet if requested. I’ve had a seriously busy time over the last few months and became a little overrun with everything. I hope this article puts things right!
And so, we reach the end of another bee year, and, as I write,
just a few Common carder bumblebees are still in evidence in the garden. The red mason and leafcutter bees are long gone but mud and leaf filled tubes in the bee nesters are evidence that their work has been done. Another generation is already in place and will emerge next spring and summer. But will it? Are bee nesters a fit and forget option in our gardens? Will the bees emerge and happily go on year after year? Sadly, the answer is probably not.
By attracting these bees to our gardens, we are encouraging
them to nest in far higher densities than would occur in nature. As a consequence, parasites find bee nesters just as welcoming as the bees themselves. Left unchecked, pests and disease can completely wipe out your bee nester population in a relatively short period of time. It should be our duty to open, inspect, clean, and replace
used nesting tubes annually to ensure the health of our solitary bee guests. At home this has been my best ever year for red mason bees with around 600 sealed tubes by the end of their flight period.
The ‘unwanted guests’ in the bee nesters include mites, flies and parasitic wasps which can all have a highly detrimental effect on the intended occupants. No matter how well maintained, bee nesters will attract a certain amount of unwelcome attention during the course of a season.
I use a combination of routed out trays, cardboard tubes with paper liners and (though some would frown upon it) bamboo tubes drilled out to appropriate sizes. I have never had a problem with bamboo but have found that the percentage of parasitised or failed cells is higher in the wooden trays than cardboard or bamboo tubes; I now only employ the tube option.
When all of the activity has ceased I move my nesters into a sheltered part of the garden to protect them from rain and to allow the bees to pupate, and the metamorphosis into adult bees to take place. In nature the bees would remain quiescent in their cocoons until spring but at this point I step in to give them a helping hand.
Bamboo cane upon opening – infested with mites
The ‘Pests’
Details of the lifecycles of the following creatures are available on the internet, so I will concentrate on illustrating how to keep their numbers in check for the wellbeing of our bees.
Mites Chaetodactylus osmiae: One cell is heavily infested with mites. The black specks on the left of the healthy cocoon are larval droppings; this is completely normal. Red mason bee larvae move
the droppings out of the way before spinning their cocoon, whereas leafcutter bees incorporate droppings in theirs. The mites are the flesh- coloured mass to the right of the yellow powder (mite droppings).
Cacxoenus indigator – a kleptoparasite fly: These fruit flies enter bee nesters through the nesting tube entrance, laying their eggs when the bee is away from her nest. When the eggs she lays hatch out, the grubs consume the pollen that was meant for the bee larvae and the bee grubs starve to death. If only a few eggs are laid, you just end up with a small mason bee but a larger amount means no bee at all.
2018 – a good year for Red mason bees (Photograph by Chris Hawkridge
Monodontomeros obscurus: These tiny little wasps (around 4mm in length) can be particularly troublesome especially in nesters that are populated with thin-walled plant stems or unprotected paper straws. Cardboard or bamboo tubes seem to be proof against their attacks, at least in my experience. This is a wasp which can oviposit up to 10 eggs into a cocoon. The resulting larvae then
eat the developing bee and overwinter as fully developed larvae within the infested cocoons. Reject any cocoons that don’t feel ‘right’. A healthy cocoon is firm to the touch, though male cocoons sometimes have dimples in them. Keep any you are not sure of in an escape-proof container and see what emerges in the spring.
Safe opening of bamboo tubes
Never allow children to do this unsupervised. It can be a little dangerous opening bamboo tubes as I found out to my cost a few years ago. All you need to open a bamboo tube safely is a simple device like the one shown. This consists of a length of 75mm x 50 timber screwed to a base of 150 x 25. Two holes about 120mm deep are drilled into the 75 x 50 which are large enough for the bamboo tubes to sit in. Then if you insert a sharp knife about 10mm deep across the entry end of the tube and twist it gently left and right
Safe opening of bamboo tubes
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