Further information on poly hives
With no crown board and a solid flat roof the beekeeper with experience only of wooden hives may be concerned about the lack of ventilation in poly hives but experience shows that poly hives need no upper ventilation. This has been proven on the tens if not hundreds of thousands of poly hives in use around the world. Where poly hives do have ventilation is the floor. All current poly hives have varroa floors and the overwhelming consensus of opinion is that the varroa tray should be left out all year round - including right through the winter. This provides ventilation at the lowest point of the hive, allowing the warm air to rise, and the colony to conserve its heat with lowest input of energy - i.e. consumption of stores.
In some cold countries, such as Finland, the varroa trays are usually replaced in early spring to encourage brood rearing but this is not common in the UK, perhaps because in the UK damp is the greater danger than cold.
Queen Excluders and Clearing Supers
These two subjects are grouped together because there are some similarities. Plastic queen excluders are often supplied with poly hives, but wooden framed metal queen excluders can also be used. Care needs to be taken that the bee spaces above and below the queen excluder are maintained. The same applies with clearer boards, although here the issue is less critical as clearer boards are used only for a short while, unlike queen excluders. It is also possible to use unframed metal queen excluders with some designs, but as the details vary between different makes, it is difficult to give specific advice and the recommendations of the hive supplier should be taken into consideration.
A different strategy is not to use any queen excluder. This is not uncommon in Europe with poly hives and the success of this method is probably linked to the better thermal insulation of the poly hive - which will keep the queen at the bottom of the hive as she will be less inclined to seek the warmth near the top of the hive - which can happen with wooden hives when the queen excluder is dispensed with. The advantage of no queen excluder is of course the bees are not hindered in their movement upwards into the super and with an unconfined brood volume the queen should always have space to lay, providing supers are added when required. However, not using a queen excluder is not recommended for beginners, as it makes inspections potentially much more difficult and as it is not something commonly practised in the UK the beekeeper will find little advice from outside sources.
Woodpeckers and Other Pests.
Poly hives can be attacked by woodpeckers just as wooden hives are and the same protection measures can be used - nets, old CDs, etc. There is no evidence that poly hives are more or less vulnerable.
Wax moth larvae can cause damage, particularly the Greater Wax moth, but most damage can be avoided by good hygiene on stored items - ensuring they are stored clean and without old comb present. The area around the varroa tray can become attractive to the Lesser Wax moth, whose larvae feed on the debris falling through the varroa mesh. Damage can be avoided by keeping this region clear and especially by not leaving the varroa tray in place for any extended period.
Other than woodpeckers and wax moths, poly hives are more or less resistant to all other forms of attack from common pests. The hives do not rot when wet and most designs feature low entrances which prevent mice entering the hive. Separate mouse guards are thus not used on these poly hives.
Poly Hives - Environmental Issues.
The environmental issues surrounding poly hives are a subject about which strong opinions have been voiced, although with the growing acceptance of this type of hive in the UK this debate is not as topical as it used to be.
Leaving the more emotive arguments to one side, a good poly hive will last 30 or so years, so it is not quite in the same league as, say, plastic packaging. Disposal of poly hives is a potential problem but the material can be broken up and used, either as roof insulation, or a soil conditioner for heavy soils - after being cleaned and sterilised first. Further information on this subject can be found on the following website. Although aimed mainly at the use of EPS in the packaging and construction industries the environmental issues discussed are appropriate to the use of EPS in beekeeping. See here for details
Other uses of EPS in Beekeeping
As well as hives, EPS is also widely used in queen rearing, where it is arguably more established in the UK than it is for full sized hives. The proprietary mini-nuc, the Apidea, is very commonly used for mating queens, as it needs only about a cupful of bees to stock. Other versions are also available, for example the Swi-Bine from Swienty which is very similar in size to the Apidea or the Mini BiVo that is smaller. These poly mini-nucs use very few bees, so heat conservation is a critical factor and the high thermal insulation of EPS in these tiny hives must play a significant role in their success. Larger mini-nucs are also available, such as the Kieler, Kirchain or Warnholz, which are similar forms of small top-bar hives. Larger still are so-called mini-hives, which are built like a conventional poly hive and take 6 Dadant Shallow depth frames, albeit frames of half the normal width. These mini-hives have separate floors, bodies and roofs so they can be stacked with several bodies on the same floor - in which configuration they can successfully over-winter as a small colony before being split again the following season for further queen rearing. Over-wintering in Apideas and Kielers has been achieved but the chances of success decrease with mini-nuc size.
Full sized nucleus hives are also available in EPS and commonly take 5 or 6 frames. As with mini-nucs, their increased insulation over a wooden equivalent is reported by many beekeepers to be a major advantage. Designs differ and range from a simple moulded box with a solid floor to designs little different from a full sized hive - with varroa floors and the ability to add boxes as the nuc expands. Internal feeders or space for fondant are also a features of some designs.