Honour the pollinators of your crops: you can thank a pollinator for one in every three bites of food that you take. Thirty five percent of our crops rely on insects, birds or animals to pollinate them.
What is pollination? When bees and other animals move around flowers, they take pollen, which forms on the male part of the flowers, the anthers, and move it to the pistils, or female parts of the flowers. If the pollen lands in the right spot, it moves down through the pistils, to the eggs, which are inside the flower.
Pollination is also brought about by wind and water. Pollination comes before fertilization, and fertilization results directly in the plant producing seeds and fruits. Seeds, of course, are the means by which plants manage to disperse to new sites.
Seeds and fruits are also food for many people and ani
Insect Pollinators Of Crops
We tend to think that honeybees are the only pollinators. While honeybees do pollinate the vast majority of crops, there are many other insects, birds and small mammals that do a similar job.
Other bees such as leafcutter and carpenter bees, for example, are pollinators of lucerne plants, while the carpenter bees pollinate the rooibos tea plant. These other bees are involved in pollinating a number of different fruits and vegetables.
South Africa has the largest population worldwide of pollen wasps. These wasps feed their larvae on pollen and nectar, like bees, and not on insects and arachnids like other wasps. They also pollinate the rooibos plant, along with some nut trees and subtropical fruits such as granadillas, avocadoes, litchis, papaya and mangoes.
Certain long-tongued flies (Nemestrinidae, Tabanidae, Bombyliidae) one of which is the horse fly are effective pollinators. Some of them specialise in flowers that form part of the cut flower industry. Others pollinate subtropical fruits and some nuts.
Mammal Crop Pollinators
Surprisingly, rodents also act as pollinators, although they tend to work more in the floral kingdom than in pollinating fruit or vegetable flowers. Plants have adapted to bring this about. They produce blossoms close to the ground, are dull coloured and produce a yeasty scent during the evening. They time this in tune with the nocturnal activities of rodents.
And not only rats and mice, but even Cape grey mongooses and large-spotted genets have been captured in photos with pollen all over their faces. Another smaller South African mammal with a taste for nectar is the Cape Rock sengi (Elephantulus edwardii) – a member of the strange-looking elephant shrew family.
Bats are also pollinators. The baobab tree, which provides shelter and food for an abundance of animals, is bat pollinated. And if you have the large agave cacti on your plot you will also need bats to pollinate them.
To attract these flying mammals flowering plants have evolved a musty or rotten perfume. Some plant species have evolved acoustic features in their flowers that make the echo of the bat’s ultrasonic call more conspicuous to their bat pollinators. Bats service many plants that we use for medicinal, cultural and economic purposes.
More Insect and Bird Pollinators
Some beetles also play a pollinating role, often of plants with bright (red, orange or yellow) odourless flowers. Many beetle species eat pollen. So the plants they visit must produce ample amounts of pollen to make sure that there is enough left to pollinate the flower after the beetles are finished eating.
Moth and butterfly pollination is relatively common in the summer rainfall region. They also help with some sub-tropical fruits.
Ants pollinate some nut flowers, while calliphorid flies and ladybirds contribute to onion pollination.
Bird pollination is well known in Africa, with sunbirds, sugarbirds and several other bird species visiting flowers regularly.
When it comes to crops, honeybees are responsible for pollinating sunflowers, nut tree flowers, berries, citrus, subtropical and deciduous fruits, melons and watermelons. The vegetables they pollinate include pumpkin, most of the squashes, cauliflower, broccoli, Brussels sprouts, onion, carrots and cabbage.
On a larger scale, crop farmers need beekeepers to bring honeybee hives to their farms for the few weeks the crop is in flower. This is to provide the high density of bees needed for good pollination. Honeybees are highly mobile and visit many different flowers of the same species over a fairly wide area as they feed. The indigenous South African honeybees are therefore vital to South Africa’s food productivity. Beekeepers manage their bees at the scale needed for our intensive large-scale crops.
However, honeybees and most other pollinators face threats: diminishing habitat and forage resources, pests, diseases and inappropriate agro-chemical regimes that misuse pesticides or insecticides in the agricultural environment.
How Can We Protect Pollinators?
The following practices will protect pollinators and improve the soil’s fertility and structure:
- Minimal tillage of soil.
- Crop rotation with legumes.
- No burning.
- Planting of cover crops such as legumes on unplanted lands will provide nitrogen to the soil and nectar and pollen to pollinators.
- Intercropping (the growing of two or more crops closely together) will create diverse farming systems.
- Planting of trees in and around fields will mimic the natural environment and allow beneficial insects to thrive.
Leaving areas of a smallholding uncultivated will provide the necessary habitat for pollinators to thrive. Carpenter Bees depend on logs for their nests and honeybees may build nests in tree cavities or termite mounds. Mason Bees use clay and Leaf Cutter Bees use leaves.
A strip of uncultivated land around a smallholder field can also act as a windbreak which helps to reduce soil erosion. The removal of invasive weeds before they go to seed will ensure that they do not invade natural areas.
Natural areas are important safe havens for pollinators and ensure that other ecosystem services continue. Not only do natural enemies of crop pests benefit from these areas, but they also serve as carbon sinks that reduce greenhouse gases.
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