Author: Geoff Porter, OVA Natural Environment Committee
When we think of insect pollinators, bees probably come to mind. Supping coffee in our garden recently, it was good to see insects feasting on the Michaelmas daisies. Whilst from a distance, they appeared to be bees, closer inspection revealed that all but one were hoverflies. Wasps, beetles, butterflies, moths and flies are all important pollinators. In the UK, honeybee hives have declined by 50% since 1985, thirteen native bees have become extinct and a further 35 are at risk. In Europe, 1 in 10 bee species are also facing extinction. It’s estimated that in the UK, insects have declined by 60% in the past 20 years.
The reduction in bee numbers has resulted in more attention being paid to hoverflies. Research has found that they visit 72% of global food-crops and 70% of wildflowers and the larval stage of some species also consume aphids and other small insects. Bees, being communal insects have a limited home range whilst solitary hoverflies can travel large distances, carrying pollen on their hair. Bees feed nectar to their larvae whilst it’s consumed by some adult hoverflies. It’s estimated that butterflies and moths visit 54% of flowering plants.
Hoverflies are ‘true flies’, belonging to the family Syrphidae in the order Diptera. There are over 200 members in this family in the UK. Adults are very varied in appearance but most are black and yellow, often resembling wasps and bees. All are harmless. Whilst some adults survive the winter, most are short-lived. The lives of larvae are diverse; whilst most eat nectar or pollen, others feast on aphids, (a bonus for arable farmers), some rotten wood, a few in wasp and bee nests where they eat dead adults and other detritus. A few live in water. Whilst the majority are natives, others, like the aptly named marmalade hoverfly, migrate with southerly winds from Europe, often in large numbers. Many species don’t have common names.
The continuing decline of pollinating insects is of great concern. Their demise is due to habitat loss, intensive farming, climate change and pesticides, especially systemic products that contain neonicotinoid, (neonics for short), identified as being especially toxic to insects. This chemical enters all parts of treated plants; leaves, flowers, roots, stems, pollen and nectar. The poison attacks insects’ central nervous systems. It’s not selective; it doesn’t just kill ‘pests’. Its use is banned across Europe but it is contained in 36 pesticides still available in the UK. The Government has granted annual exceptions for sugar-beet growers to use thiamethoxam, to prevent yellows virus which is spread by aphids, by coating seeds with the chemical. The Government is about to decide whether to extend its use for a fourth year.
As well as entering the sugarbeet plant, the poison leaches into and contaminates the soil, wetlands and water-courses. It’s active in soil for some 3 years, so any flowering plant taking up this systemic insecticide could poisons their pollinators. The Rivers Trust and Wildlife and Country Link have both found one or more nicotinoids in 10% of English rivers tested by the Environment Agency. At 55% of those sites, neonicotinoids were found at levels deemed by the EU to be unsafe for aquatic life.
Barnaby Coupe, manager with the Wildlife Trusts voiced serious concern that despite growing evidence, the continued use of neonicotinoid is increasingly polluting the environment whilst Gareth Morgan, policy head of the Soil Association pointed out that organic and agroecological farmers manage to produce food without the use of these pesticides. The chemical is also found in acetamiprid, used to treat cereal seed crops and in products used on both fruit trees and in commercial glasshouses. Garden products such as Bugclear Ultra and Rose Clear have been identified as highly toxic to pollinators. In Response, DEFRA has stated that they are tackling every source of water pollution while ensuring pesticides do not harm ‘people’ or pose unacceptable risks to rivers.
What you can do to help:
All pollinators are precious, not just bees! So, please value them all. You can play your part by avoiding pesticides and providing a variety of habitats for insects in your garden.
Sources:
- Proceedings of the Royal Society, Biological Sciences: ‘Pollination by hoverflies in the Anthropocene’.- (current geological age).
- The Bee Keepers Association.
- Article ‘Bee-killing pesticides found at high levels in English rivers.’
- The Guardian. 23rd Sept.2023.