Tuesday 3 May 2016

The significance of the decline in world bee populations and why do our pears sometimes lack seeds?

There is a fashionable meme that if we lose our bees we will all starve. This is complete nonsense. Don’t get me wrong, I don’t deny that  bee populations are threatened and that bees are magnificent creatures who play a fundamental role in the pollination of many crops and flowers and that we must do everything possible to preserve them.

My story today starts when my friend Peter somewhat disingenuously wrote to a supermarket chain and mentioned that he had noticed that their magnificent pears seemed to lack seed.

The reply would do credit to a moonlighting Lyra Silvertongue. The reply is 100% correct and a masterpiece in product promotion

Thank you for sharing your observation.
Our commercial British apples and pear growers all aim to produce apples and pears with good seed set.
This is because;
1) As seeds develop with the fruits they naturally release hormones which will promote the growth of flesh and result in larger fruit size (and therefore positively impact on crop yield).
2) Fruits with evenly set seeds are more likely to meet the Horticultural Marketing standard for Class I quality and therefore get higher return i.e less misshapen fruit.
3) Fruits with evenly set seeds typically store better.

For this reason  a significant number of our growers introduce bees (honey bees and solitary bees) to their orchards and preserve species biodiversity in wind breaks to provide habitat for over wintering insects which play a role in pollinating their crops in the spring.

Many of our growers are also involved in research projects with East Malling Research, (improving pollination in pear orchards), Southampton University (improving habitat around periphery of apple orchard to improve pollination) and Reading University. (improving ecosystem services within apple orchards)

There are a couple of reasons for reduced numbers or absence of seeds depending on variety and all linked to poor conditions at pollination - e.g extreme temperatures which abort pollen tube growth and development inhibiting the pollen from fertilising the ovary and forming the seed or low temperatures which reduce insect activity.

The Royal Gala variety which you specifically mention is a particularly precocious variety and even in years when conditions for pollination are poor it still tends to set a large number of apples and it is usual for the flesh of Gala to continue to grow following a poor pollination period without the presence of seeds (known as parthenocarpic development) - hence the reason for lack of seeds in this variety.
It is possible that in years when weather conditions are poor, (cold and wet, growers sometimes apply naturally produced hormone ‘gibberellin’ to  improve skin finish on apple and pear varieties prone to rough russet e.g Conference pears and Cox .  These gibberellins' are safe and legal and under certain weather conditions can stimulate the development of parthenocarpic fruit (virgin fruit) which could also explain an absence of seeds in varieties such as Cox.

This is a very helpful letter and I think its technical content is very interesting. The sting in the tail is in the last paragraph. I do not wish to condemn this technical innovation, I personally think the use of gibberellin is something to celebrate as I will discuss in a moment.

 A really lovely Cox that Peter bought at his local supermarket

Only one seed!

A full set of seed

Core blimey

Why the threat to world food production by the loss of bees is relatively small.

Not all bees are declining, far more other organisms sustain pollination than assumed and most of world crops are wind pollinated and do not require animal pollination at all. Nor must we overlook new innovations that might aid pollination

Taking the last point first! In excess of 80% percent of the world’s food production is from wind pollinated crops or those that do not require pollination. 

Wind pollinated grasses dominate world crop production albeit not this ornamental plant

It is truly amazing and not a little disturbing that almost 90% of the world’s nutrition comes from a basket of five.
The annual production of these five crops - in ballpark figures - are
Maize 900 million tons
Rice 750 million tons
Wheat 700 million tons 
Potatoes 400 million tons
Cassava 250 million tons

(Its a little confusing when you check out such figures. For example sugar cane comes in at a whopping 2 billion tons. More relevant is the amount of refined sugar - about 175 million tons. My figures today are much rounded and will vary with how yields are expressed in the literature e.g if expressed in monetary value they give no indication of quantity)

Potatoes are vegetatively propagated from stem tubers (and alarmingly some consider them threatened by virulent new natural sexual strains of potato blight).
Sugar cane is propagated by division and so are bananas. Bananas are interesting because from ancient times they have been selected to be seedless. With no seedling variation they are threatened by the scourge of Panama disease. Not all crops are secure but my argument today is about crop loss caused by the absence of bees.

For many crops the edible part does not need pollination. This does not mean that bees are not needed for seedsmen to produce seed.

Worldwide there are 20,000 species of bee - although only 2% of these do most of the bee pollination. There are real fears about honeybees and there appears to be a perfect storm of pest and disease, habitat loss, agricultural mono-cropping, pollution and spraying of pesticides such as neonicotinoids. Loss of hives frequently seems to be some kind of sickening symbiosis.
Sturdier bumble bees sometimes are more significant pollinators than honey bees. They are in decline too.

Its not all gloom and doom. Worldwide research investigates how to overcome bee problems and if solutions are found nature has a great capacity to bounce back.

Although bees have no significant role in pollinating wind pollinated crops, their pollen can be a source of nutrition for bees

Not only do the less common bees contribute to crop pollination, so do a myriad of other unheralded insects, mites and spiders - and so many more. Their contribution is often overlooked when worrying about bees

Ant on blackthorn

Ant on dandelion
Butterfly on sedum
Gibberellins and other technical solutions to the absence of bee pollination
I think we can almost discount hand pollination although this is important in private gardens and a few specialist labour intensive crops. Potentially plant breeders might bring us more seedless fruits such as grapes.  More self pollinated fruits can be bred. There is scope for innovative introductions of pollinating insects in protected environments.

Gibberellins are already used worldwide where pollination is difficult. As Peter’s letter points out it is a perfectly natural and harmless material sprayed onto the flowers. It is a natural plant hormone which is fundamental to many natural plant growth processes such as controlling seed dormancy and fruit development.
A huge range of crops already benefit from growers’ use of gibberellin, not least apples and pears. A quick search of the net shows it to be often used on blueberries, melons, grapefruit, oranges  tomatoes and grapes - and that is just scratching the surface.

Bumble bee on my own stonecrop. Every little helps

Preserving the bees
Although the thrust of this article suggests we would survive without bees it is almost unthinkable that we should need to do so. 
There are many popular articles that show how gardeners can help with bee conservation and I have previously posted my own.

Some of the bees flitting in my own bonnet are....
Recognising the value of bee friendly plants wherever they come from.
Not insisting that planting schemes in wild places only use native plants. We need plants of the world and their hybrids if we are best to preserve natural environments.
More purposeful planting of pollinator friendly plants on agricultural fringes and not giving grants satisfied by only growing a few weeds.
Recognition of trees and shrubs as copious sources of nectar and their diverse planting in farming areas to ensure continuity of season
More locally focussed measures in fruit growing areas.

The bees knees
Thank you Peter and Cathi for the pictures

This link takes you to my previous four articles on bees


  1. Sarah Raven presented a programme some time ago where she tried to encourage councils away from sterile bedding schemes but many seem to stick with salvias and the like. With the threats to green belt what we plant in our urban gardens will be increasingly important.

    I could have done with some pollinators in our greenhouse when the soft fruit trees were flowering - it was hard work being a bee. No honey bees equals no honey but I do wish many people (not you) wouldn't assess a creatures right to exist based on the impact they have on us.

    Deleted the last comment as I spotted a typo.

    1. What a typo from you Sue (thought they were your trademark)

    2. Cheeky - my eyes aren't as bad now so hopefully typos will reduce. Using voice recognition can be problematic.

    3. I know you don't mind me being cheeky. And I have followed the saga of your eyes on your own blog.. and its moral, go to a local small optician!

    4. I wouldn't recognise you if you weren't cheeky, Roger.

  2. I wonder how many gardeners are taking great care to provide nectar plants, but forget about nesting sites. I have a small bare patch of sunny dry ground in my 'lawn', and every spring I see little miner bees building their underground nests, followed by little cuckoo bees that search for the carefully hidden chambers. They are only around for a couple of weeks, while the willow is in flower. I had intended to put a terrace in that spot, but I can't bring myself to do it. I would destroy the next generation, and quite possibly the colony, if it were the case that they hatch, forage and then return to the same spot. Bumblebees are equally vulnerable, especially the ones in my compost heap, I feel horribly guilty when I see queen bee searching for her lost nest.
    My totally unproven theory is that suitable nest sites are possibly a bigger problem than nectar supply, and if the solitary bees tend to stay in a small area, the population numbers would easy be damaged by disturbance. We already know that some butterflies stay in quite a small area, and with just a two week breeding period it seems possible to me that this could apply to some bees too.
    Another good argument for not digging :-)
    p.s.I'm not surprised Sue makes typos, this silly little box to type in makes it very hard to see what you have written!!!

  3. It is good that we sometimes put to one side having a pristine garden to enhance wildlife and provide ecological interest. I sometimes get more pleasure from an interesting 'pest' than the plant itself.
    You are a great thinker about your garden. I wanted to say 'the thinking man's gardener' but that is rather sexist.
    As to longer replies I sometimes have trouble on an i pad when my words of wisdom freeze. It's a good idea to type out in Word or Pages and cut and paste into the silly little box!


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