Half of my hives are within a few hundred metres of fields that are filled with OSR on 4 year rotation, and the resulting affect on my bees are both a pleasure and a pain. It’s appearance makes me wince, knowing from past experience what is coming. The upside of a bumper crop is great but the downside of trying to keep colonies queen-right and in the box is going to be a trial that I know will keep me on my toes, not to mention the time consuming process of getting OSR honey into the jar.
Last year there were fields of yellow all around and, as expected, the bees were on the flowers as soon as they opened, squadrons of foragers returning with sack loads of yellow pollen. The colonies built up fast, swarm control was a challenge, but the spring weather was as we all experienced, very bizarre, unseasonally hot, then wet, then cold, and so it continued for the rest of the year. The resulting problems with mating and associated colony and nucleus failures have been well reported, but the effect on honey production was a surprise. When it came to the first harvest, the filled supers were not as expected.
There was honey, but only a handful of frames contained OSR, despite the acreage planted all around our locality. It was a puzzle. The fields had flowered for almost a month and the bees had been on it as the pollen observed had confirmed, but where was the honey? A nearby beekeeper reported the same and that their bees had flown right over the fields right next to his hives to forage on other sources such as Hawthorn. Not having experienced this before I wondered if a new variety had been sown. Further investigation was required and involved contacting the local farmers for their thoughts. To my surprise they reported bumper yields from their crops, best they’d ever had, and from the same varieties they had been using previously. The only noteworthy thing was that when checking their crops, which involves physically walking into the field of growing plants, they reported that they were unusually heavily covered in the waxy substance that the plants naturally have on their stems and leaves. More research was called for, and I eventually discovered the answer in an agronomy paper.
The Brassica napus plant, it turns out, is a well studied species with many varieties that possess some interesting traits. Amongst them is vernalization, the use of seasonal cues to growing, and the ability to respond to environmental factors such as weather conditions. Vernalization allows the crop to be sown in the autumn when it germinates and produces its initial leaf rosette which lies dormant on the soil surface through the winter then grows on as temperatures begin rising, to flower in late spring. Another is it’s ability to control moisture by coating itself in a layer of cuticular wax, which is hydrophobic and impermeable to water and other soluble substances. It does this naturally to protect itself from biotic and abiotic stresses and can increase it’s thickness when required to act, for instance, as sun protection, or to lock in moisture. It is why during last years very hot and dry weather the farmer’s clothes were heavily soiled with wax, and what helped the plant reduce transpiration and contain what moisture was available during the hot dry weather despite it’s long tap root. At the same time the plant used another trait, VPD (atmospheric Vapour Pressure Deficit) in response to drought stress, to divert what moisture was available to seed production instead of nectar. Pollen production is not affected in the same way as this is necessary for germination and seed production for future reproduction and survival. The lack of OSR honey in the supers was simply Brassica napus using it’s clever traits to trade off limited resources from nectar production to favour seed production and ensure species survival.
The research article, while explaining the anomaly of the missing honey, is an interesting study into predicting OSR flora resource availability using agronomic trait data in order to include ‘floral resource value’ in future OSR breeding programmes and varietal recommendation initiatives. The results of the study could be used in future to produce pollinator friendly varieties of OSR as an alternative to high-performing varieties for conscientious growers to consider in response to concerns over the decline of insect pollinators.
Agronomic Traits in Oilseed Rape (Brassica napus) Can Predict Foraging Resources for Insect Pollinators.
