Yesterday evening I went to a talk on “Bee foraging on garden plants: Sussex University research” by Professor Francis Ratnieks at the Jodrell Lecture Theatre, Kew Gardens. Francis is the Professor of Apiculture (Evolution, Behaviour and Environment) at the University of Surrey – the only Professor of Apiculture we have in the UK!
Before the talk began, a student read some gardening themed poetry for us, which I enjoyed. The poems included ‘Tree at my Window’ by Robert Frost and ‘Come slowly – Eden!’ by Emily Dickinson. Prof. Ratnieks must be a fan of poetry too, as he began his talk by quoting a line by Rudyard Kipling:
There’s a whisper down the field where the year has shot her yield, And the ricks stand gray to the sun, Singing: — “Over then, come over, for the bee has quit the clover, And your English summer’s done.”
He then went on to discussing his research, which has covered many different topics to do with bee health and foraging behaviour over the years. He has done research to try and find out the main pollinators for commercial crops such as apples, pears and blueberries in the UK. One of his studies in East Kent found that 61% of insects visiting pear & apple flowers were honey bees, while a similar May 2012 study of blueberry flowers found 65% of insect visitors were honey bees. This was despite the blueberry farmer having put out hundreds of bought-in bumble bee colonies (Bombus Terrestius) amongst his crops. Pollination is big business now, with US beekeepers paid $175 per pollinating hive for the Californian almond crop.
Honey bees on apple flowers
It may surprise some readers to hear that he considers the two main threats to bees to be diseases and fewer flowers in the countryside/habitat loss/intensive farming – not pesticides, climate change, mobile phones or any of the sensational stories the media likes covering! This correlates with the views of Dr Stuart Roberts, whose talk on the decline of insect pollinators I blogged about last year.
Flower research
We are losing large patches of common flowers such as knapweed and ragwort. These flowers are not going to go extinct, but they are the bread-and-butter of honey bee foraging.
Quite often books suggest that people plant spring flowers, to get colonies going early in the year. Yet Professor Ratnieks has found that the average distance foraged by honey bee colonies he studied in March was 1/2 kilometre. In July, this increased to 2km. The reason for this? In spring, bees find it in easy to find flowers, whereas in summer they have to go further. Despite the warm weather of summer, in terms of planting available forage it is then that bees really need our help, more so than in winter. Don’t bother planting flowers for bees in January – they will only have about one day’s foraging time.
Ragwort – this pretty yellow flower gives the bees both nectar and bright yellow pollen.
Ivy flowers in autumn.
In autumn ivy comes along and acts as an incredibly important late source of forage, providing both nectar and pollen. Professor Ratnieks found that 91% of all pollen collected by his bees during mid-Sept to mid-Oct was ivy pollen. He told us he’d come to the conclusion that “If ivy wasn’t invented already then it probably should be”. And yet its unshowy flowers go unnoticed and unappreciated by many.
The best plants for bees
July and August (in the UK, anyway) is when bees need the most help, so if you want to encourage the animated soft hum of happy bees in your garden, give them summer flowering garden plants.
A study by a Phd student Professor Ratnieks supervised, comparing around 32 common garden plants, found that there was a 100-fold range in attractiveness to insects between the best and worst plants. The worst plant was a red pelagonia, which attracted nothing! The best plants were…
Lavender – especially good for bumble bees
Borage – especially good for honey bees and other insects too
Majoram – attracted a wide variety of insects
Now, you might ask: why do bumbles prefer lavender and honey bees borage? Professor Ratnieks believes that the delicate flowers of borage are more suited in size to little honey bees, rather than big, bouncy bumbles.
Bumble bee landing on borage – it happens occasionally!
As for lavender attracting bumbles more often, this is likely to be because bumbles are faster on the lavender flowers. Bumble bee species tend to have longer tongues than honey bees, which enables them to collect nectar from each lavender flower in a speedy 1.5 seconds. In comparison the shorter tongued honey bees must really stick their tongue out, and end up taking around 3.5 seconds per flower.
Each lavender flower contains a minute amount of nectar, so the extra couple of seconds makes a real difference in foraging efficiency.
Shortening some lavender flowers with cuts reduced the times honey bees spent visiting each flower, thus backing up the theory that it is their shorter tongue slowing them down. In a further experiment with lavender flowers, Professor Ratnieks devised a ‘High-Tech Whacking Stick’. This crucial piece of equipment was a stick wielded by his research students. They used it to selectively deter bees from visiting two different patches of lavender – in one patch bumbles were excluded, while in another honey bees were excluded. A third control patch with no bees excluded was also used.
What the students found was that when bumble bees were excluded, honey bee foragers quickly built up on the lavender. Whereas on the control patch where bumbles were not excluded, there were hardly any honey bees present. It appears to be the case that bumbles deter honey bees from visiting lavender by being quicker than them – there’s almost no point the honey bees trying.
‘Bowles’s Mauve’ wallflower – best for butterflies
A plant for butterfly fans. Butterflies are harder to attract than bees, mostly because there are fewer of them. A British butterfly won’t lay her eggs on a non-native plant, so bear this in mind.
Honey bee on borage. Courtesy The Food and Environment Research Agency (Fera), Crown Copyright.
Differences between urban and rural honey bee foraging
Oil seed rape is an important UK crop; it will soon be the 2nd biggest arable crop in England. Professor Ratnieks decided to study just how often foraging honey bees around Brighton visited oil seed rape, which is renowned for being attractive to bees. His results were surprising to me – in Brighton most foragers stayed in the city and ignored the oil seed rape fields within their foraging range, while on average the rural colonies surrounding Brighton visited the rape field for about 10-20% of their foraging. This was determined by both studying waggle dances and collecting pollen samples.
Professor Ratnieks had expected the figure for rural colonies visiting oil seed rape to be higher, as these were big fields. If colonies are not choosing to collect the majority of their nectar and pollen from oil-seed rape that is good news, as it will help them avoid the pesticides commonly used on rape crops.
As an aside, Professor Ratnieks commented that he feels the number of hives in central London now is “ridiculous”. Companies have been installing hives on their rooftop to increase their green credentials, without any understanding of the sustainability issues. In his view the whole of central London would need to be converted into fields of borage in order to properly support the hives currently there.
Lots of beekeepers say that towns are better for bees than countryside; he believes it is not so much that towns are good for bees as that the UK countryside is crap! We have turned our countryside into a desert of monocrops.
There is a video about the research available on YouTube, narrated by Professor Ratnieks – Quantifying variation among garden plants in attractiveness to bees and other insects. Thanks to @MerryBeeBo for letting me know about this in her comment on this post.
Oxalic acid research
Prof. Ratnieks noted that the UK National Bee Unit had not done any research comparing the efficiency of oxalic acid treatments by the different methods of vaporisation, spraying and drizzling. He realised that such research would be cheap to carry it out, so set about doing it himself.
The results surprised me – vaporisation was the most effective way of killing varroa using oxalic acid, and also resulted in no bee deaths. Spraying oxalic acid was the most toxic method, though only resulted in a couple of bees per day dying in the week after application. The advice I have seen given in BBKA News before has been that vaporisation requires too much care in handling to be worth it (the fumes can be toxic to humans), but if it is significantly more effective perhaps our Association should be looking into doing it that way.
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