The Management of Honeybees for Oil Seed Rape
A talk by Lynne Ingram, February 2020
There was a good turnout of East Devon and West Dorset beekeepers to welcome Lynne back for another of her thought provoking talks. A quick show of hands revealed that the majority of the audience viewed oil seed rape (OSR) a curse to beekeeping, a view that Lynne was hoping to dispel.
Today, the crop makes a valuable contribution to the British economy, estimated at more than £650 million. It has in fact been in use for 4000 years and there are records of its use in 1649 for soap and oil production. The domestic market started in the 1950s and got a boost in the 1960s due to the newly perceived benefits of polyunsaturated fats found in rape seed oil.
In addition, the oilseed cake residue was a valuable animal feed. However, it became apparent that the erucic acid content of the varieties used at the time was causing heart damage. This brought about the introduction of low erucic acid varieties through plant breeding.
Another group of compounds found in oilseed cake were the glucosinolates, causing damage to thyroid and pituitary glands of animals fed large quantities of the material. This too was reduced by plant breeding, leading to the current ‘double low’ varieties.
More recently the 2013 ban on neonicotinoids has resulted in reduced plantings of OSR and lower yields.
What is OSR?
All varieties are derived from Brassica napus, a member of the cabbage Family. Winter sown crops will usually flower in mid-April for about 3 weeks whereas spring sown varieties drilled in early April will flower in July. Pollen and nectar are produced in huge quantities, with the added bonus that depleted nectaries are rapidly refilled. OSR can be partially wind pollinated but insect pollination increases the seed yield.
The advantages of OSR are the potential for a large crop of naturally setting, finely crystallised honey which can be used as a ‘seed’ for other honeys that are reluctant to set. Disadvantages include setting in the comb, possible poor flavour perception, lower yields with modern hybrid varieties and the need to process immediately the honey is ripe.
The perceived downside to OSR cropping usually relates to the rapid onset of crystallisation of the capped honey due to the high glucose content of the nectar. In order to overcome this problem Lynne outlined her strategy.
Lynne’s management strategy
If you intend to take advantage of OSR for honey production the colonies will need to be large and vigorous, so late winter/early spring feeding with 50:50 sugar syrup to stimulate egg laying will be required. Contact feeders are best. Pollen patties may also be needed to supply the extra protein for the brood production.
- Prepare your site and time the move so that there is plenty of nectar available straight away.
- During the flow, regular inspections will be needed to prevent possible swarming.
- Ensure ample supering as it takes around 3x more space to process nectar as the ultimate volume of ripe honey.
- Remove and process capped honey as it ripens. Immediate processing will minimise crystallisation.
- Make sure you know when spraying will take place.
- After the flow you will have large colonies with most of the stores removed, so ensure there is adequate space in the hives for the large colonies and feed if necessary.
Lynne recommended extracting any liquid honey and then scraping back partially set honey to the midrib to recover as much as possible. Any residue can be sprayed with water and replaced on the hive. Fully set honey has to be cut out of the frames, packed into tubs and warmed at 55°C for 12 hours. The wax rises up as a mush and eventually separates from the melted honey. Allow to cool to 30°C before pouring the honey off.
The procedure for bottling tubs of set OSR honey is to warm the set material until it is ‘porridgey’ at around 32°C, stir until smooth, allow to settle, then bottle and store at 14°C to optimise setting. If full filtering has not been achieved before putting in bulk tubs, the honey will have to be warmed sufficiently to flow through the filter. With partially crystallised honey this can be troublesome.
To prepare soft set / creamed honey with a 10% ‘seed’ of OSR honey, first warm your floral honey until liquid (up to 50°C) and cool to 30°C. Warm the ‘seed’ honey until ‘porridgey’ (c32°C) then combine the two portions with stirring, avoiding the introduction of air. Allow to settle, then bottle and store at 14°C. Recommended long term storage temperature is 10°C.
Question & Answer session
During the Question & Answer session the notable topic was temper of the bees during and after the OSR was in flower. Lynne explained this could be caused by removal of stores causing defensive behaviour. Any situation where there are unemployed and overcrowded foragers will tend to cause problems. There is also a “starvation” scenario which can arise from dietary insufficiency as well as lack of quantity for a very full nest, possibly the effect of erucic acid. Lynne stated she has not had too much bad temper as there are usually other high-yielding sources coming on, notably field beans.
The flowers of OSR have 4 petals, 4 sepals, 6 stamens (4 long and 2 short) and 4 nectaries (2 inner and 2 outer nectaries). The nectar is produced mainly by the inner nectaries and is capable of being replenished in ½hr after a visit by a forager.
The nectar of OSR has a higher concentration of glucose then fructose which leads to rapid crystallisation with a fine crystal structure. The highest sugar concentrations are at the beginning of the crop so timing your arrival at the site is crucial.