Beware! Is your ‘bee hotel’ a nursery for disease and pests?
Or put another way, why does n’t my bee hotel work and increase my wild bees? I wish, from my experience as a researcher, educator, designer, user and producer of bee boxes, to shed light on the controversy over the effectiveness or otherwise of bee hotels. The controversy is to do with the design and construction of bee hotels that, it can be argued, have a significant influence on the survival outcomes for bees. Researchers have just published what I have found myself, that bee hotels are not what they appear!
From a customer AM, who bought a bee hotel from another supplier;
‘Did what you said had a look at the bees and sadly they were all dead having been eaten by tiny grubs, how can I be sure this doesn’t happen again. I am really upset., as I looked after them all winter keeping under a porch out of all weathers’.
In their paper ‘Bee Hotels’ as Tools For Native Pollinator Conservation: A Premature Verdict? they found ” at their worst, bee hotels may act as a population sink for bees through facilitating the increase of parasites, predators….and diseases”
You could call me biased as I build and sell award winning bumblebee and solitary bee boxes but nevertheless from both my experiences over the years and that of other researchers there is substantial evidence that different bee hotels are more effective than others. Some designs just don’t work, have harmful or minimal outputs for bees in terms of survival from predators, disease and environmental factors.
Successful or otherwise?
To me a success is not if the solitary bees use the nest box. Highly like some will. It is a success if a new generation of solitary bees emerges from it the following year and better still in more numbers.
I believe the key considerations when considering the effectiveness of bee hotels is the ease of management along with how it is designed. Annual and informed management is essential to improve the positive outcomes for bees. Just as you manage the countryside and urban green spaces and in particular nature reserves to improve the outcomes for birds, mammals and plants there is a need to manage insects, including bees for a positive outcome. Some of us wish to do the same with our gardens. Unmanaged bee hotels of certain designs and materials may have their place but the evidence is increasing that the positive outcomes for bees can be minimal or even negative. I invite you to consider my discussion below to enlighten you about the controversy over bee hotels and make up your own mind.
This is my two penneth!!
I have made some videos and given a few explanations as to my experiences as why many bee hotels can actually kill bees in my garden. I show several other methods for attracting wild bees/wasps and thoughts you may wish to consider before placing them out. I regard myself as a wild bee keeper, especially red mason and leaf cutter bees and as such, like a honey bee keeper, I want to manage my garden bees and protect them from pests, predators and the like. A few species of solitary wasps have used my nest boxes. Different pests I have come across, require different control measures, which can also depend upon the nest material in use. My advice would be, if you can’t open it to clean it, don’t buy it! With home made/collected materials at the very least they should be changed annually.
A slick marketing name for people to remember! There is a huge choice of designs, materials etc., out there nowadays, some look really good and pleasing to the eye! Firstly they are not bee hotels! Other insects may use them as an ‘insect hotel’ for temporary resting, shelter or feeding places. The solitary bees, e.g. red mason bees, live as cocoons inside the cavities from late spring to the next spring. Other bees do likewise from summer to summer as do some solitary wasps. Hardly a hotel, more a bee home!
What will use them?
Its not like a bird nest box, when you can say in the main, which birds will use it. Other than a few bees and solitary wasps that I do know, which other bees or solitary wasps will use them I have no idea. It is a question most people in the UK cannot answer. Other than a book about solitary wasps Prof. Sarah Corbet, there a very few solitary bee/wasps academics here and finding a book on the subject is frustrating! Though I can fully appreciate the time, effort and expertise needed to write one! I believe one is being written……and BWARS is a useful site if you have the patience to try to find the wasps/bees inside your nest box and then match them with the web site photos! Then you see one that looks like it to discover there’s another that looks exactly the same!! At least its a start!
Is your ‘bee hotel’ a nursery for disease and pests?
There may well be many unwelcome guests, all after the rich pollen/nectar mix or even the bee egg, larvae or cocoons themselves.
Pollen Mites (Chaetodactylus spp.)
Pollen mites attach themselves to bees using huge claws, (above) drop off on flowers, feed up, mate and hitch a return lift courtesy of another bee. Once inside the safe environment of a red mason bee’s cell, they breed and can soon become many thousands inside one cell, outcompeting the bee larvae for food, leading to its death or reduce the size of the bee. Smaller female bees have reduced fecundity. For the bee larvae, it is a race against time. According to some researchers, they may also eat the egg before it hatches and even certain later stages of larval development.
new film with new research
To cater for environmental factors within the cell, probably food scarcity or decreasing humidity, they have developed a survival strategy. Some become migratory mites and migrate as described, waiting till spring when the bee leaves its cell or as it passes through a mite infested cell, often found in huge numbers that it can affect the flight of the bee.
The above mites probably moved out of the natal cell as there is evidence of Cacoxenus indagator frass which means they may have ate most of the pollen which forced them to leave and encyst
The remaining mites, as above, encyst and are non migratory. They remain in situ inside your solitary bee nest until some environmental cue triggers their activity. Its a survival strategy that works as they can remain dormant during unfavourable conditions for several years. Your bee nest may well now contain many 1000’s. These methods enable them to maintain their normal host relationship and disperse to gain new hosts.
Nest to nest dispersal
Other than those that hitch a lift (phoresy) on a bee, mites will also disperse within solitary bee nests by walking to nearby nest entrance holes, walking from nest to nest through splits, cracks, holes, gaps, and parasitic wasp emergence holes, all of which can be found in wood, straws, canes, reeds, paper/cardboard tubes.
Wasps and other pests
In my garden, parasitoid wasps, such as Monodontomerus wasps can devastate red mason cocoons, likewise Pteromalus wasps with leaf cutter bees. Artifically large numbers of solitary bees will produce a huge amount of frass. Parasitoid wasps in particular seek out and can recognise their hosts frass, which gives off chemical cues. Manage these to stop them eating your bees! For me, that’s essential.
Other pests will seek out pollen stores/larvae/cocoons all concentrated in one easy to find location. Many of these pests may otherwise be scarce in wild populations.
Wasps such as ruby tailed, Sapyga quinquepunctata and the cuckoo bee Coelioxys spp. are minor cleptoparasitic pests in comparison to the parasitoid wasps, as is the Houdini fly, Cacoxenus indagator. in my garden currently. This may change as these things do in nature!
A fungal disease caused by Ascosphaera spp. (not the honey bee species) infects the bee larvae and kills them. It is scarce in wild populations. Under managed and high densities of bee populations, it has the ability to rapidly spread. Its spores have been found to live for many years. The spread of this disease has to be prevented. Your old solitary bee nest may be a source.
If a diseased bee dies inside its cocoon, the bee further inside the cavity will have to chew through its body as they exit. If they don’t they will die inside. The spores,fungus, disease can be picked up by all exiting bees in that cavity. This may not kill the bees themselves, but certainly the disease will spread to flowers they visit and passed onto other bees visiting them. Their own offspring may themselves be infected as spores drop from the adult bee to infect the pollen that is consumed by the larvae. They will die.
Moisture cannot wick away causing fungal infection of the pollen and the bee larvae die. Raw states “Glass tubes have been found undesirable, because condensation on the inside of the tube killed the occupants”
The tubes are a real pain to clean for adults and children. They made management of the bees very difficult. I want to observe bees and their parasites. I want to increase bee numbers, not kill them!
Cheap, cheerful but a false logic?
Well intentioned but woefully inadequate
Drilled wooden blocks, a simple to make DIY attempt, is now old technology and again allows for the increase of pests and diseases inside each hole. Management of them is impossible.
Upon first impressions the above drilled log appears to be a great success with high occupancy. It probably is, for pests!! The splits make it very easy for pests to migrate from one cell to the next and easy for solitary wasps to parasitise the cocoons. Inserting paper rolls inside is fiddly and any gaps can allow wasps to enter, but can help with pollen mites. They have to be a tight fit and be able to be pulled out. They are liable to get wet in the rain without adequate shelter. It may be a good idea to replace wooden blocks, logs, annually to help prevent pest/disease build up.
Wide windy opened ended tunnels are not liked by solitary bees!
Bamboo tubes are tough, waterproof, cheap and cheerful and should be changed annualy. They are easily replaced and with experience, time spent cutting, sorting re lengths, width etc., can be made to work very well and allows for management of bee cocoons. Inserting paper rolls inside is fiddly and any gaps can allow wasps to enter, bamboo diameters can be variable. Many shop bought ones have nodes halfway down making them smaller or even blocked by a node at the entrance! Many of these are simply too wide and again act like wind tunnels. The brittle sharp edges have not been clean cut and are not very friendly to bee wings! Any cracks or splits would be exploited by parasitic wasps.
Opening bamboo canes to check for bee cocoons
I was asked to advise about red mason bees and offered to examine their old bamboo bee nest, which had been put up for years to encourage red mason bees to use in their showcase orchard, as part of a well known and beautiful garden in the North West. It had not been managed. It may have been put out for the bees but had it been used and what was the result?
The canes were split open to allow us to see what was inside and more importantly, how many red mason bees cocoons there were to pollinate the apples.
Out of all those canes we were left with just a few cocoons, which MAY have been viable ones! Bamboo canes need replacing annually.
Even phragmites canes can be attacked by Monodontomerus wasps…..and allow pollen mites to enter
Reed, plant stems, cardboard tubes and straws
High holed densities may favour the spread of diseases, pests, mites. The different shapes, lengths, positions make it easier for solitary bees/wasps to find their own actual nest. Would need replacing annually. Can be very successful. In the distant past I used hogweed stems, but got no takers. So I don’t bother now!
Reed and plant stems can be very effective for solitary bees and wasps, but open to attack by Monodontomerus wasps and without protection, birds and mice. Wood makes an excellent container to house bamboo, reeds, etc. Metal is not good idea. You may find the bees are overheated, the nectar may dry up and worst the bees are cooked! Unless of course you put a shelter roof over it or remove it before it gets too hot.
They have to be thick enough to stop monodontomerus wasps ovispositing through them and having a sealed back end is required. They need to be protected from the rain and are best kept inside a waterproof container with an overhanging roof, or the protruding end gets wet. They work admirably but can start to become expensive. Some people put a paper liner inside to help make cleaning them easier. I don’t use these anymore.
Grooved boards as bee nests
These work but need cleaning and managed. You cannot see what is going on and have to unscrew them disturbing the fragile bee larvae if you want to watch them. They were put up next to one another in the same year. The old one I had not used for a few years. It had not therefore been cleaned and I left it like that to see how it performed. The other one on the left was brand new. You can see the bees preferred the new unused one to the old one.
Birds and mice
The British green wood pecker has a 10cm long tongue which is so long it has to be wrapped inside its skull and the greater spotted woodpeckers tongue can extend 4cm out of its mouth. A mesh in front of the nest box is hardly a deterrent with a long barbed tongue. Great tits also relish bee cocoons, as do mice when bee cocoons are left in situ inside reeds or bamboo canes or stored without adequate protection. Managing against such predators will increase your solitary bees. The nest blocks I use you simply turn the whole nesting unit around so they now face the inner wall!
Several negative aspects affect the nest box position. If you position the nest box in the wrong place, I have found pests such as ants and earwigs soon find them, both of which can eat the pollen and eggs. Spiders can also take up residence! Weather, wind, rain, shelter, damp and vegetation can all have negative effects.
The way and means the nest box is affixed to its permanent place can have negative effects on the bee boxes and consequently the bees.
Solitary bees and solitary wasps build cells inside cavities. The length, width and materials used all have a bearing on the success or otherwise for the occupants.
This is what I designed to help eliminate many of the above problems with management.
Why use Wooden Nesting Blocks by Nurturing Nature?
Many Solitary bees prefer to use wood to nest in
Easily cleaned and removed from nest box casing
Nest box casing design and dead end cavities allows for additional materials to be added to minimise parasitoid wasps
Easily viewed for inspection and pest/debris removal
Absorbs excess moisture by wicking it away from moist pollen reducing likelihood of mould formation which destroys cells
Long term investment, natural resource, reuse many times over
Harvesting of cocoons simplified (kids love this aspect!)
With management has the potential to increase your red mason bee pollinators
The dead-end cavities are easily adapted to cater for different solitary bees and harmless solitary wasps
The cavities are designed to save the bees time and encourage more females
Allows ‘loose cell’ or closed ‘cell management’
Widely spaced holes avoids high hole density nest finding confusion
24 reusable cavities for bees, 6 holes per nest block x 4 per nest box
Full detailed instructions and personal after care service.