If your garden has seemed different in recent years, with that familiar buzz much quieter, the air less colourful and alive, it’s probably not your imagination. Bee and butterfly populations face alarming declines worldwide. That’s a scary thought, considering that most of the crops we eat rely on these (formerly) frequent visitors.
It’s true that no one person can single-handedly restore the monarch butterfly and reverse the honeybees’ downward spiral, but as we work on the larger issues at play, like climate change and widespread pesticide use, pollinators need safe spaces to feed and find mates. That’s where you come in: make your own yard a pollinator-friendly pit stop with a few simple fixes.
Why are bees so important?
Bees are such a precious part of our ecosystem, and there has been some concern about their well-being over the last few years. It is thought that certain pesticides as well as mass monoculture farming are playing a key role in weakening their immune systems, causing colony collapse, and declining numbers. Loss of habitat and urbanisation are also taking their toll. This problem is far more severe in the industrialised northern hemisphere but is starting to gain ground in South Africa too.
By making your garden a biodiverse haven, you can play your part in keeping the bees thriving as an indispensable part of our ecosystem.
It’s important to make sure that you are not using nasty pesticides in your garden that are known to contain bee-harming chemicals such as neonicotinoids. Read your labels – they usually contain acetamiprid, clothianidin, imidacloprid, and/or thiamethoxam as active ingredients. Explore greener, healthier pest control options.
Plants that bees love
The most important step you can take is to plant a pollinator-friendly garden. Choose nectar- and pollen-rich plants such as vygies, rosemary, sunflowers, thyme, lavender,agapanthus and fruit trees.
Some more bee-loving tips
Bees are especially attracted to purple, violet, blue, blue-green, yellow, ultraviolet, and white flowers, and they prefer scented flowers.
Plant flowers that bloom at different times of the year to keep the bees well fed year-round.
A bee bath needs to be shallower than a bird bath – a shallow tray-like bath of water is ideal. You can also put some marbles in a shallow pan and fill it with water – that way the bees will have somewhere to land and drink.
Care for our Butterflies
If you want the privilege of these floating jewels in your garden, you’ll need to make peace with a few munching caterpillars, because that’s how butterflies start off. To encourage butterflies in your garden means you must allow for the larval stage too – your garden should serve as a sanctuary to nurture and protect the butterfly throughout the stages of its life.
Go lightly on pesticides and only use them when necessary, to give caterpillars a fighting chance as they are already pitted against plenty of natural predators. especially if you are creating a diverse ecosystem in your garden. Toxic pesticides can also get into the plant nectar that adult butterflies drink.
Plants that butterflies love
Our top picks to include in your garden to attract butterflies are Cape plumbago, Cape honeysuckle, butterfly bush, lavender, daisies and impatiens.
Some more butterfly-loving tips
When it comes to flowers, butterflies like colours ranging from blue to mauve, red, pink or white.
Some butterflies like rotting fruit such as bananas or pineapple, so leave some fruit from your fruit trees to rot on the ground as food.
They like to get some minerals from pockets of mud too, so a little mud puddle or two will be appreciated.
Bringing insects back into our garden
Let’s aim to bring back all the beneficial insects back into our garden and appreciate them for all pollinating services they provide. They buzzing of the bees and the colourfulness of butterflies definitely puts a smile on our faces.
We need insects in our garden, so use a product that only controls the pests.
Insects are necessary in our gardens. They play an important role in the natural ecosystems that keep our gardens healthy and alive. As such, using blanket pesticides with the intention of killing pests, can wreak havoc on all insect populations, and is not only irresponsible, but also counterproductive. Our gardens need biodiversity and balance. Without this balance keeping your garden healthy can be tricky. This is where using a product like EcoBuz Pest Pro comes in useful.
Some pests, that are insects, that do need to be controlled are red spider mite, whitefly, tomato leaf miner and false codling moth, and Pest Pro is registered for all of these.
Red spider mite pests
Red spider mite pests can be a real pain, especially in dry conditions during summer. They breed and spread rapidly, are difficult to detect, and require perseverance and persistence to control them once they have established themselves. Look out for tell-tale signs of infestation: discolouration of the upper leaf surface, lack of new growth, and plants looking dull and lacklustre. These pests need to be controlled as they suck the sap from the leaves, causing plants to lose condition rapidly.
Whitefly can be difficult to control because as soon as you start to spray they fly off and settle on another plant. They suck the sap of plants, weakening them and also potentially transmitting disease. Like red spider mites, they are particularly problematic during the hot months, although they prefer humidity.
Tomato leaf miner pests
Tomatoes suffer from many diseases and pests under the sun, one of which is tomato leaf miner. The little pests, which are the larvae of moths, ‘mine’ their way through the leaves of the host plant, creating trails that can be seen on the leaves. In low numbers these larvae cause just cosmetic damage, but if the population explodes then the damage can affect the plant’s health and crop, also making it more vulnerable to other afflictions.
False codling moth pests
It is the larvae or caterpillars of the false codling moth that causes the damage. They hatch after the adult lays the leaves on the surface of the fruit (avocadoes, citrus, macadamias, grapes, etc) and then burrow into the fruit. Not only do these pests eat away at the inside of the fruit, but the holes they create in the surface allow entry to other pests and diseases.
Pest Pro contains spores of the beneficial fungi Beauvaria bassiana – a soil-borne fungi that occurs naturally and commonly in many soils. The strain used in Pest Pro was originally isolated from beneath a rooibos plant in Clanwilliam and is well adapted to the hot, dry conditions of our country. Pest Pro is a 100% South African product, comprehensively researched, developed and commercialised in KZN. Pest Pro is well established in the local agricultural industry and is currently being registered in the EU and USA. Pest Pro (Reg No L 10579, Act 36 of 1947) is a biological pest-control solution that is safe, non-toxic and friendly to beneficial insects including bees, ladybirds, parasitoid wasps, lacewings, earthworms, birds and fish. Pest Pro is also OMRI certified (Organic).
How does Pest Pro work?
Pest Pro applications are recommended as a foliar spray. Best efficacy is obtained with direct contact of the target pests, so ensure good coverage of the affected foliage and flowers or fruit. It is important to note that whitefly and red spider mite are commonly found on the underside of leaves, so ensure you reach these areas. When spores make contact with the pests (or are ingested), they germinate, penetrate, grow and multiply inside the body, ultimately resulting in the death of the pest. This process takes 3 – 5 days, but pest behaviour alters much sooner. Pest Pro is effective on all life stages – insects, eggs and larvae. Three applications are recommended at 7 – 14-day intervals.
Important info when using biological products such as Pest Pro
Because the active ingredient in Pest Pro is a fungus, the use of broad spectrum fungicides should be avoided for at least three days before and after applications. For increased efficacy applications should be made during the late afternoon or early evening as spores are UV sensitive.
Summer has arrived and so have the creepy crawlies. For many garden lovers the detection of caterpillars in their veggie gardens is soul destroying, normally for two very different reasons. Firstly, the devastation of their attack and the inevitable ruin and damage to your efforts and harvest. Secondly, and often most importantly, you are then faced with the really tough decision as to ‘if’ and ‘how’ you should get rid of them…
The good news is that there is now a safe and effective biological larvicide for the control and management of a wide range of caterpillars. What is meant by the term ‘biological larvicide’? Larvicides specifically target the ‘larval’ stage of an insect and ‘biological’, as you know from previous issues, refers to the introduction of a natural enemy.
The natural enemy in question, Bacillus thuringiensis (Bt), is a beneficial soil-borne bacteria occurring naturally in soils. Bt is one of the first commercialised and most successful biocontrol products globally, and has been used since the 1950s for natural insect control. Bt is highly adaptive to different environments and is target specific, only being toxic to lepidopteran larvae. Bt has no effect on beneficial insects such as bees, ladybirds, lacewings and predatory wasps.
Larvae Pro is a commercial product that forms part of the EcoBuz Bio-Protect range and contains spores of the beneficial bacteria Bacillus thuringiensis (Bt) subspecies Kurstaki strain SA-11.
How does it work on caterpillars?
The Bt spores are activated when mixed with water. The solution needs to be sprayed onto foliage and plants affected by caterpillars, where the spores will germinate and multiply. They need to be ingested by the larvae in order to be effective, and this is achieved when the caterpillars feeds on treated plant material. Each Bt spore contains a special protein crystal that once ingested becomes active in the alkaline gut of the larvae to form a toxin that paralyses and ultimately kills the larvae.
Larvae Pro is highly specific. The Bt crystal contained in the Larvae Pro spore only activates in the alkaline gut of Lepidopteran larvae. Lepidoptera (moths and butterflies) is the second largest order in the class Insecta. Nearly all lepidopteran larvae are called caterpillars, and have well-developed heads and chewing mouth parts for feeding on plants, which makes them a common pest in gardens and agricultural crops.
Larvae Pro is easy to mix and apply, with consistent results. Spray onto the affected area as soon as caterpillars are detected, taking care to cover both the surface and underneath of leaves. Once ingested larvae will stop feeding within 24 hours and die within a few days. Larvae Pro treatment will be faster and more effective on small, young larvae. Most importantly, Larvae Pro is nontoxic, completely natural and OMRI listed (Organic Materials Review Institute). It is safe for use, for consumers and the environment, it has no withholding period so you can spray today and eat today. Larvae Pro is registered for the suppression of African bollworm, tomato leaf miner and fall armyworm on crops as listed.
This particular bacterium, or disease, is one of the good guys, keeping fungal outbreaks under control.
It’s easy to see things happening in the spring garden: shoots peak out of the soil, leaves unfoil, buds burst open and everything grows seemingly overnight. But there is as much, perhaps even more, happening that we can’t see with the naked eye.
Behind that patina of spring colour and new life is a fierce battle raging throughout the garden, above the soil and below its surface, on leaves and amongst roots. Microbes are locked in territorial warfare, competing for space and resources to ensure their own survival and their expansion.
We tend to think of bacteria and fungi in the garden as the bad guys, to be eliminated in the pursuit of a pristine and ‘clean’ landscape, but some of these microbes need to be there, are beneficial and play a vital part in the garden’s ecosystem.
One of these bacterial ‘good guys’ is Bacillus amyloliquefaciens (Ba), discovered in 1943 and intensely researched since then for its properties as a plant growth stimulant and broad-spectrum biofungicide. Ba is a beneficial bacterium that occurs naturally in soils, and is now globally recognised as an effective, nontoxic biofungicide that is widely used in agriculture and suitable for use in organic production. Ba is now available on retailers’ shelves as EcoBuz Disease Pro, offering home gardeners a biological disease-management alternative.
Disease Pro offers a natural disease-management solution that has no impact on the environment or beneficial insects, pets or children playing in it. It is also residue-free and has no withholding period, which means that edibles can be harvested after being treated and immediately eaten. You can literally apply Disease Pro, pick a fruit and eat it, totally safely.
Disease Pro is an excellent resistance management product, helping to prevent pathogens from becoming resistant to a particular treatment. Due to its unique mode of action it may be used in a program to avoid routine spraying of the same chemical actives, which can result in resistant disease populations that become very difficult to manage. It can also be used in conjunction with and at the same time as chemical fungicides (excluding copper based products).
More about Disease Pro:
The ‘active ingredient’ in Disease Pro consists of Ba (strain D747) bacterial spores, which are mixed with water and then applied to plant surfaces, where they germinate and grow. Disease Pro supresses powdery mildew and downy mildew, and is registered as such on a number of crops such as table grapes and cucurbits (the pumpkin and squash family).
Disease Pro produces substances (antimicrobial metabolites) that prevent the growth of fungi and other bacteria.
Disease Pro is fast growing and quickly colonises plant surfaces, competing for limited nutrients and space. This makes it difficult for diseases to get established.
Disease Pro boosts the plants natural immune system, which over time improves the plant’s resistance and makes it less susceptible to pathogens.
Disease Pro works best as a preventative spray, applied before the onset of a fungal infection. If you know that you live in a damp area or that your garden is prone to mildew infections, inoculate susceptible plants before mildew becomes a problem. The Ba spores will quickly colonise the plant surfaces, occupying space and resources that the mildew or other pathogens would need to become established. Apply weekly with a minimum of three applications. So get out there and get multiplying those spores!
We always say, “you are what you eat”, and most of us think we’re being healthy when we eat five servings of fruit and veg a day. But do we really know what we’re eating? When we buy a punnet of plums or a bag of kale from the supermarket, do we know what they were sprayed with while growing or after they were picked? No we don’t, which is the real benefit of eating plants you planted, nurtured and harvested in your own garden – you can control what goes onto them, and therefore what goes into your body. This is why we all need to be talking more about biological control, or ‘biologicals’.
Simply explained, biological refers to a natural ‘circle of life’ – the predator and prey relationship found in nature, like a lion catching a springbuck. The lion kills something, which is gruesome, but there’s no collateral damage – only the springbok is hurt. With biologicals we take that part of nature and focus it to benefit our gardens – we take the natural enemies of a pest in our garden, and we use them to keep the pest (and only the pest) under control: birds eat caterpillars, ladybirds eat aphids, and beneficial bacteria, viruses and fungi keep other pests and diseases in check.
A biological approach, or biologicals, centres around nature, embracing the synergistic relationships that occur naturally to ensure survival and sustainability. ‘Biologicals’ view nature as being brilliantly creative and diverse – with soil (a living ecosystem) being integrally interconnected with roots and plant health. As an example of the complexity of the soil ecosystem, there are about a million fungal and bacterial organisms in a single teaspoon of soil, each of them playing a part in the natural cycle of life in the garden.
If you want an example of how effective biologicals can be in pest control, look no further than the declining infestations of prickly pears in South Africa. At the beginning of the 20th century prickly pear was a big problem, taking over swathes of agricultural land. Then clever scientists introduced a little cochineal bug, which did its thing and got prickly pear under control. Port Jackson willow is another local biological success story, where a gall-forming rust fungus and a midge have both proven to be effective control agents.
More relevantly to us and our veggie gardens, tomato plants are very susceptible to Phytophthora root rot, caused by phytophthora fungus-like organisms. Inoculating your soil with biologicals like the spores of the Trichoderma asperellum fungus, which colonises root systems and protects them, can control this. The result – no more root rot, and no chemicals needed!
Another problem we all face is the caterpillars that always arrive when we plant cabbages or mustard, or any member of the cabbage family. If you spray your plants with the Bacillus thuringiensis (Bt) beneficial bacteria, the caterpillars will stop eating and eventually die, and if a bird eats them it’s no problem.
A range of biological pest control products is finally available on local retailer shelves. Keep an eye out for the new EcoBuz brand and the four biological products launched in spring 2019. This exciting new development introduces biologicals: safe, effective pest-control solutions that don’t compromise the health of beneficial insects, birds, pets, people or soils and the environment.
Benefits of Ecobuz biological products, or biologicals, for edible gardeners:
No residuals – this is of great significance with all edible crops as it means applications can be applied right up to harvest. (Each product is unique, so always check the packaging and inserts for specific details.)
Biological product ‘mode of action’ is unique in comparison to chemical counterparts. This makes these products ideal for use in rotation with chemical treatments to prevent and manage pest resistance (where frequent and repeated use of the same chemicals results in a pest no longer being susceptible to its effect).
Gardening is biology, revolving around the biological processes of growth and life. For millions of years, plants have thrived and grown successfully with no human intervention.
Chemical pest control and plant nutrition have become the norm over the past 80 years, though, with many negative side effects recently emerging. The good news is that new natural innovations, offering a long-term holistic alternative, are now emerging – ‘biologicals’ for biological gardening.
A biological gardening approach centres around nature, embracing the synergistic relationships that occur naturally to ensure survival and sustainability. As gardeners we have been taught to view bacteria as germs, fungi as diseases, and insects and weeds as pests. However, the scientific truth is that many of these critters are beneficial, even essential, to healthy plant growth and development. When there is an excess of one pest species it is often an indication that the natural balance has been disturbed and an indication of vulnerability.
Natural biological control takes place continuously, in its own unique way, within every ecosystem. Using a garden as an example, biological pest control would include everything from birds feeding on grubs to owls catching rats, to ladybirds keeping aphids under control, or parasitic wasps laying their eggs on caterpillars. Even competitor plants such as alien invasives influence the ecosystem of a garden.
Finally, gardeners need to be aware that there are good pathogens – beneficial bacteria, fungi and viruses that feed on microbes and insects. There are also bacteria that are good for the soil, as probiotics are good for your stomach.
Biological products contain the naturally occurring enemies of crop pests and diseases, as well as organisms that facilitate improved root growth and nutrient uptake. These living organisms may be fungi, bacteria or viruses, in environmentally friendly and easy-to-use formulations, excellent for biological gardening.
Although perceived as a relatively new science, this technology dates back to the late 19th century, but has experienced a re-emergence with the decreasing faith in chemical agriculture. The process of identifying, screening, isolating, testing and mass producing microbes can take decades and in order for biological products to be sold commercially, they need to adhere to the same stringent controls as synthetic products in terms of efficacy and application.
Several strains of fungi and bacteria have been identified to be effective in the control and management of pests and diseases. Each has a unique mode-ofaction. For example, the fungal spores of Beauveria bassiana attach and penetrate through the ‘skin’ of whitefly, spider mite and various other insect pests when contact is made. The fungus grows and multiplies inside the insect, ultimately resulting in death. Similarly, beneficial bacteria Bacillus amyloliquefaciens colonises plant surfaces, occupying space at potential infection sites, utilising nutrient sources and making it difficult for pathogens such as powdery mildew to get established.
Biopesticides are not a ‘soft option’, but offer highly effective pest-management solutions. Due to their natural presence and relative host specificity they are safe for the environment, non-toxic to non-target organisms like bees, beneficial insects, pets and, most importantly, children. In addition, most bio-pesticides are residue free and can be applied to edible crops right up to harvest. They also act in a way that is unique when compared to their chemical counterparts. This makes them ideal for use in rotation with synthetic chemistry to prevent and manage pest resistance – a process whereby frequent use of the same chemistry results in a pest organism no longer being susceptible to its effect.
What does all this mean for biological gardening?
The goal of sustainable biological gardening is to grow healthy plants, in a healthy environment with minimal impact on the environment. Biopesticides offer natural, non-chemical alternatives. These may not be as immediate and as impactful as a synthetic pesticide, because they take a little longer to take effect, but they are just as effective as their chemical counterparts and should be the first option in your garden’s pest management program.
Bees are classified according to common character traits
Bees can be classified in many different ways. Their taxonomic classification uses shared characters that are indicative of relatedness between species, and this is best expressed as an evolutionary tree. However, nest architecture, sociality and floral biology can also be used to classify bees. According to taxonomic classification, any species can only belong to one group. Other classification systems cross taxonomic boundaries, and species groups will differ according to the classification criteria. Buzz pollinators, for example, will include some carpenters and some diggers, but neither all carpenter nor all diggers. The different classification systems have their uses.
South African bees are divided into six cosmopolitan families. Four of them (Melittidae, Colletidae, Andrenidae and Halictidae) are short-tongued bees. They may be able to extend their mouthparts a long way into tubular flowers, but then the entire mouthparts will be elongated and not just the tongue. Two families are long-tongued bees (Apidae, Megachilidae). The South African pollen-collecting bees can all quite easily be placed into families using The Bee Genera and Subgenera of sub-Saharan Africa (http://www.abctaxa.be/volumes/vol-7-bees/). This booklet can also be used for identifying bee genera and sub-genera.
Bees construct their nests, and the cells within their nests, in many different ways. Some of these are unique to a taxonomic group: all leafcutter bees belong to the genus Megachile, but not all Megachile speciesare leafcutters – some are daubers or resin bees. Carder bees belong to several closely related genera. Mining tunnels into the ground occurs in many unrelated genera (and in different families), and boring into wood occurs in both long-tongued bee families. Knowing their nest architecture is useful for specific purposes. Tunnel-nesting bees, for example, only inhabit bee hotels, which are artificially provided tunnels for bees, usually in wood. Bees with similar nests could behave quite differently in them. Some small carpenter bees are social, with very small colonies, whereas others are solitary.
Most bees nest in cavities, while some have exposed nests. The best-known cavity nests are those of honeybees – they live naturally in holes in trees and in the ground, and are kept by beekeepers in hives. Stingless bees inhabit cavities similar to those of honeybees, but smaller, and they don’t dig their own cavities. All other cavity nests are tunnels. Some bore their own tunnels (miner and carpenter bees), while others use existing insect burrows, including those of other bees. They mostly raise their larvae in cells within their nests. Exposed nests are usually made of mud (daubers), resin (resin bees) or plant fibre combed to look like cotton wool (carder bees). Daubers, resin bees and carders have either exposed or cavity nests.
Exposed nests of dauber and resin bees are spherical, comprising several oval cells packed closely together. The whole nest, after all the cells have been constructed and provisioned, is rounded off into a ball with mud and/or resin. Carder bees simply have a ball of ‘cotton wool’ in which cells are constructed.
Among the cavity nesters, honeybees make cells out of wax (honeycomb). They use similar cells to store pollen and honey (made from nectar) that they feed to their larvae. Stingless bees have larval cells and much larger pots, also made from a waxy material, for storing honey and pollen. Only honey and stingless bees store food for their larvae outside brood cells. Other pollen- and nectar-collecting bees provision a brood cell and lay an egg in each cell. The materials used to make brood cells are reflected in their names: sand or mud (masons), resin (resin bees), wood shavings (carpenters), leaf or petal (leaf cutters), cellophane secretions (hyaline and plaster bees) or cottony fibre (carders).
Some bees do not collect pollen, namely males and parasitic bees. They are therefore not important pollinators. Most parasitic bees are cuckoos, meaning they lay their eggs in other bees’ nests. The parasite kills the host’s larva and feeds on its provisions. Social parasites replace, or co-exist with, queens of other social species. The host species’ workers raise the parasites larvae. Parasitic bees therefore do not construct nests.
Why are there so many female bees?
In bees, fertilised eggs develop into females and unfertilised eggs develop into males (therefore females have twice as many chromosomes as males). After mating, females store the sperm in a spermatheca and are able to control which egg cells are fertilised, thus they can determine whether they lay female or male eggs. This enables social bees, including honeybees, to have a hive full of female workers and only a few males – when needed.
Dr C. Eardley is from the Agricultural Research Council, Plant Protection Research Institute, and has worked on the taxonomy of African bees and the conservation of their biodiversity for 40 years. His email address is email@example.com.
Garden for Bees Many of you will have read that if bees become extinct, mankind will follow within a few years. Whether or not that is actually true, there is no doubt that bees play a crucial role in the pollination of our food, and they are facing a tough, tough time out there. Pesticides, herbicides, fungicides, monocultural farming, viruses, mites, a loss of habitat – these are just a few of the threats that bees are facing at the moment, and they are losing the battle in many parts of the world.
But we, the humble gardeners, can play an important part in saving bees from extinction, just by planning what we plant in our food gardens, and what chemicals we use on them.
Bees need flowers that produce both pollen and nectar, nectar from which to make honey for carbohydrates, and pollen for proteins, fats, minerals and vitamins. A hive requires a mass of bee-friendly plants flowering at any one time of the year, and preferably a variety of species that can supply a range of nutrients.
The trick is therefore to plant bunches of bee-friendly plants that flower at the same time, or bunches of one particular bee-friendly plant, at various spots in the garden. A few bunches like this that flower at different times of the year will go a long way in keeping your local bees healthy. An added bonus is that attracting bees to your garden will increase the yield of your fruits and veggies. And if you’re really keen, you could keep a hive and harvest your own honey!
TIP: Don’t forget the water! Bees need a constant, clean water source just like the rest of us. The perfect bee-bath is shallow, with sloping edges, so that they don’t drown. Alternatively, place branches and stones in a birdbath, so that bees have somewhere to land. They will also suck water out of mud.
Below is bee-friendly fruit and veggies, as well as an example diagram of how you could plant your edible garden to benefit our little pollinators.
Fruit and Veggies:
• All Year: Beetroots, carrots and onions (These only flower if you don’t harvest them, so you choose between a harvest or flowers.)
The Bee’s Perspective Flowers provide food for bees. To plants they are sex organs. The origins of flowering plants and insect pollinators began simultaneously about 100 million years ago. Cross-pollinated plants use vector, such as wind, water or an animal, mostly an insect, to deliver their pollen to a receptive stigma of another flower. Animal pollination requires that flowers attract pollinators, mostly for food (pollen, nectar and oils), but also through scent and/or visual cues. This co-evolution resulted in plants producing rewards for the service they receive, namely pollination, although the bees are blissfully unaware they’re performing a service.
Bees as Pollinators Bees are among the most important pollinators. Commonly, beetles, moths, bats and birds pollinate, and a host of other organisms may pollinate as well. Pollination precedes fertilisation in plants, but does not guarantee it. Therefore it also precedes plant reproduction, seed set and fruit production. Consequently, it is an essential ecosystem service, meaning that in the wild it directly contributes to the production of food for seed- and fruit-eating animals, and ensures that there will be future generations of plants. The same applies to agriculture. Flowers depend either on a specific pollinator, on a suite of closely related pollinators, or on many different pollinators. Similarly, some bees are adapted to forage on specific plants while others visit many different types of flowers. Specialisation reduces competition between plant species for a pollinator, and/or between bee species for the food they obtain from a specific plant species. However, specialisation is risky because if one goes extinct the other will follow. Most pollinator/plant relations are webs of activities, and these webs are poorly understood. Not all flower visitors pollinate – some steal their nectar and pollen, and contribute no benefit to the plant. They are known as robbers.
A Leaf Cutter Bee
The Flower’s Perspective To a flower, a bee is a pollen vector, and the balance between reward and pollination service must be finely tuned. The reward must be sufficient to make the pollinator’s visit worthwhile, but insufficient to completely meet the food requirements so that the pollinator is forced to visit another flower. Flowers also develop their structure in such a way that the receptive stigma touches the bee’s body in precisely the place where the pollen was lodged, either the pollen basket or another part of the bee’s body. These differences explain why we have such a beautiful array of flowers, and with them fruit and nuts – and bees. Plants have excelled beyond all other groups of organisms in producing beautiful, intricate structures to ensure sexual reproduction. Their beauty in our gardens and the wonderful variety of foods that come from these flowers is testimony to the most miraculous process in nature – biodiversity. This is nature’s way of coping in a complex, changing world.
The Bee’s Perspective Bees don’t see flowers as we see them. They see them as food. Pollination mechanisms are survival strategies for plants competing with one another for pollinators, and bees competing with one another for food. Daisies attract many different pollinators, but the anthers and stigmas are close together. Cross-pollination requires stigmas not being receptive to their own pollen. Aloes have tubular corollas suited to small and long-tongued insects. Orchids have their pollen in pollinia that they usually place on a part of the bee’s body that is inaccessible to the bee, but not to the stigma of another orchid that the bee visits. Orchids that don’t provide a reward are decoy pollinated, i.e. bees are lured to flowers by their structure and scent, but don’t receive a reward. Buzz pollination occurs in the tomato family (Solanaceae) – these plants require that a bee places it forelegs onto the anthers and then buzzes. The vibrations of its wings resonate through the forelegs and burst the anthers releasing the pollen. This is why one hears a distinct buzz every time a bee visits a tomato flower – listen next time you’re in your veggie garden!
A Yellow-Banded Carder Bee
Dr C. Eardley is from the Agricultural Research Council, Plant Protection Research Institute, and has worked on the taxonomy of African bees and the conservation of their biodiversity for 40 years. His email address is firstname.lastname@example.org.
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