The impact of oilseed rape on beekeeping
Peter W Tomkins, formerly Rothamsted Research
Rothamsted bees
Oilseed rape (OSR) was first widely grown in my area of mid-Hertfordshire and South Bedfordshire in 1976 when I was head apiarist at Rothamsted Experimental Station (now Rothamsted Research). During that late summer I developed a serious back problem and was off work for three months. My assistant managed the colonies in the traditional Rothamsted way, weighing them in September with a spring balance, and occasionally topping-up with sugar syrup where needed. No problems were anticipated. We were in for a shock!
Rothamsted colonies were run primarily for brood, bees and queens – not honey. Most of the apiary site rents were paid for with honey, some was used in experiments and a small amount in queen-cage candy.
Aſter the winter of 1976/7, we had lost 63 of 146 colonies – over 50%. Bees had died on combs solid with granulated OSR honey. Because we used only BS-deep frames and overwintered on two brood chambers, we were leſt with over 100 boxes of deep combs packed with granulated honey. We had no equipment suitable for dealing with this problem; so much was simply burned. It was a lesson learned and from then on when we extracted fully capped combs when they were ready and worthwhile. I adopted this technique with my own bees. Some honey was sold and some mixed with sugar syrup and fed back to the bees in the autumn.
However, the benefits of OSR were profound. At Rothamsted we would make increase early, usually mid-May to mid-June. These nuclei would be taken
to another apiary to prevent driſting, given a mated queen and fed. Feeding was a necessity as there was litle forage available at this time, particularly during the June gap. But with OSR forage, colonies were stronger and more able to take advantage of the main flow and this post-OSR honey was leſt for the bees as winter feed. In the past, we oſten had to purchase three tonnes of sugar each year, but OSR cut our sugar bill by 75%, a welcome saving.
With the adjustments made aſter the disastrous winter of 1976/7, colony losses returned to the more acceptable level of under 10%.
My bees
I too experienced heavy losses with my own bees during the winter of 1976/7. My 40 colonies reduced to just ten. Although it was some time before numbers were restored, my average honey crop doubled because of OSR and then trebled over the next 15 years as OSR acreage increased, culminating in a record harvest of an average of 98lbs (44kgs) per colony in 1992. This was betered in 2004 with an average of 102lbs (46kgs) – and by then I was leting the bees keep anything they collected aſter the final round of honey removal in late July, feeding fondant if needed from February onwards.
Another advantage of removing fully sealed combs of OSR honey when the crop was still in flower was that robbing was not a problem.
My average losses were also less aſter the arrival of varroa and honey yields triple those of the 1960s.
Looking to the future Recently, the area of OSR has shrunk annually (see graph on page 4) and this is likely to continue.
I think the loss of OSR will have a significant negative impact on semi-commercial and commercial beekeepers in particular and will probably impact on wild bees too. OSR makes the replacement of lost colonies so much easier and in that way makes beekeeping easier. The loss of OSR may also have a knock-on effect on the number of new beekeepers.
Bee Craſt April 2020 9
Photo: Richard Rickit
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