Blog - neonicotinoids
Bees, agrochemicals and the microbiome
Mason bees and agrochemicals The blog has reported many times on the threats to bees - money bees, bumblebees and ‘wild bees, such as mason bees / solitary bees. The threat to bees from neonicotinoids has been well documented, now there is a report that suggests that certain other agrochemicals may be harmful to bees. Researchers at the Julius Maximilians University at Würburg have been investigation the effect of a fungicide (Fenbuconazole) on the reproductive behaviour of horned mason bees (Osmia cornuta). A number of Osmia species are used to improve pollination in fruit and nut crops. They are efficient pollinators having a special pollen collecting / carrying structure called a scopa. Mason bees are solitary bees. Each female is fertile and makes her own nest and no worker bees for these species exist. In the Spring, male and female bees emerge from a nest. The males generally exit first and remain near the nest, ready to mate with the females. A female bee selects a mate on their ‘smell’ / odour and the ‘quality’ of their thoracic vibrations (achieved through muscle contractions). After mating the males soon die. The females search for and select a nest site, visiting flowers to collect pollen and nectar for their nests. Once a certain amount of food has been collected within the nest, the females lay their eggs on top of this material (in a series of cells) and then seal off the nest. The eggs hatch to form larvae which feed upon the food and within weeks forms a cocoon, in which it continues to develop to an adult. Though the fungicide (Fenbuconazole) is considered to be of low toxicity and the bees were exposed to a sub-lethal dose, nevertheless the Fenbuconazole had significant effects on the bees. Pesticide exposed males were more likely to rejected by the females, compared to ‘control’ bees that were not exposed to the fungicide. The thoracic vibrations of the exposed males were less powerful / noticeable and the composition of their odour or smell was different. The smell of the bees is dependent on particular hydrocarbon compounds in their cuticle - their exoskeleton. It is possible, therefore, that the mating behaviour and reproductive success of these bees is being affected by agrochemicals. Carpenter bees. The microbiome refers to the collection of micro-organisms that lives on or in us, particularly within within the gut. Whilst these micro-organisms are small, they contribute to our health and ‘well being’. They offer protection against pathogens, help our immune system develop, and enable us to digest. Just as we have a microbiome so do bees. Scientists as York University (Canada) have been investigating the microbiome of three species of carpenter bees (from North America, Asia and Australia). The term "carpenter bee" comes from their nesting behaviour, most species burrow into plant material such as dead wood or stems, though a few create tunnels in soil. Social bees (like honeybees and bumblebees) acquire their microbiome by interacting with their hive or nest ‘mates’. Solitary bees, like the carpenter bees, get their microbiome from the environment as they forage for food. The researchers found that: The bees’ microbiome contained Lactobacilli, which are important for good gut health, helping protect against fungal pathogens and facilitating nutrient uptake. They also discovered crop pathogens in the microbiomes of the carpenter bees which were previously only found in honeybees. Whilst these pathogens are not necessarily harmful, it is possible that the wild bees could be vectors for spreading disease. With thanks to Pixabay (Umsiedlungen and Sabinem34) for the above images of bees Finding flowers. Research at the University of Exeter has shown that bees can distinguish between various flowers through a combination of colour and pattern. This selectivity is achieved despite the ‘acuity’ of a bee’s vision being quite low (about a 100 times lower than ours) - this means they can only see the pattern of a flower when they are quite close (a matter of centimetres). The researchers analysed a significant amount of data on plants and visiting bee behaviour, and they used experiments involving artificial shapes and colours. One particular finding was the importance of the contrast between the outside of the flower and the plant’s foliage. This seemed to help beesfind their way to the flowers quickly .
Problems for bees and bumblebees.
The decline in many insect populations across the globe is worrying, threatening economies and ecosystems. A German study in 2017 indicated that the mass of flying insects (in various natural areas) had fallen by some 70%+. The decline in insect populations has been associated with habitat fragmentation, the spread of agriculture and the use of pesticides, with the neonicotinoids being particularly associated with damage to bee and bumblebee populations. Recent work at the University of Konstanz suggests that when bumblebee colonies are exposed to limited resources of nectar and exposure to the herbicide - glyphosate, then their colonies may fail. Bumblebee colonies need a good supply of nectar as a ‘fuel’ in order to maintain a constant brood temperature (of approximately 32oC). Only at this sort of temperature does the eggs & larvae develop quickly from egg to adult, and the colony grow from a single queen to several hundred bees. If the temperature is not maintained, then the brood develops slowly or not at all. The loss of wild flowers (and their nectar) plus the use of the herbicide (in agricultural areas) looks to be a problem for the bumblebees. Just as bumblebees are facing problems, so are honey bees. The bees have faced infections with a variety of viruses, such as the deformed wing virus. This virus affects wing development so that the wings are 'stubby' and useless, plus they may be deformities of the abdomen and leg paralysis; the insect cannot function and dies. The virus is transmitted by the Varroa mite - a parasite (that also feeds on the bees’ tissues). The virus was originally identified in Japan in 1980’s and is referred to as DWV-A. However, a new form of the virus (DWV-B) was identified in the Netherlands in 2001 and it is spreading across Europe, and to other continents. Sadly, this variant of the virus kills bees faster and is more easily transmitted (according to research at the Martin Luther University).
In a previous woodlands.co.uk blog, Professor Dave Goulson (University of Sussex) has written about the problems that bees and bumblebees face. Recently, he joined with Clipper teas (who produce organic tea products) to again emphasise the problems that bees and other pollinators face, and to explain how our lives would be affected if they were to be lost. Bee, bumblebee and other pollinator populations are at risk or in decline. Professor Goulson estimates that there are some 6,000 different species of pollinating insects in the U.K alone, but they face risks as a result of Habitat loss Pollution Climate change Use of pesticides (insecticides, herbicides, fungicides) [caption id="attachment_36158" align="aligncenter" width="650"] Hoverfly foraging[/caption] Whilst it is true that insecticides such as neonicotinoids are directly toxic to bees and bumblebees, many other compounds used as herbicides and fungicides are also harmful to these insects. Obviously herbicides get rid of weeds, but weeds or wild flowers are a food source for these pollinators. Pesticides can have what are termed ‘sub-lethal effects’, so that the learning ability of the insects is reduced. Bees and bumblebees can learn which flowers are best as food sources, they can navigate to and from their nests / hives through open countryside. Also these compounds can affect their resistance to disease, and their fertility / reproduction. It is a concern that that bees’ honey stores may contain a cocktail of several pesticides that the bees have encountered during their foraging. In collecting pollen and nectar, a single bee may visit / pollinate four thousands flowers in a day. Not only are many thousands of wild flowers species dependent on bees for pollination but some three quarters of our food crops also need bees and other insects. Without them, the range and availability fo fruit and vegetables in our supermarkets would be substantially reduced. Whilst going organic and reducing reliance on the many forms of pesticide agriculturally is great help to pollinators, there is also good news in that small growers and even domestic gardeners can have a positive impact on the numbers of bees and others pollinators, such as : Planting a range bee-friendly plants in their gardens Creating a wild flower area in the garden or Allowing the lawn to grow up to form a small meadow like area Reducing the use of all pesticides - insecticides, herbicides, fungicides etc.
Offer a home to a beetle, or two?
Across the globe, insects are in decline. There are several (over-lapping) causes of the decline, ranging from habitat loss, the effect of artificial lighting, the use of agrochemicals (e.g. the neonicotinoids) and herbicides, such as glyphosate. The latter is one of the most commonly used weedkillers and might not be expected to affect insects. However, recent research has shown that it can affect the formation of the hard exoskeleton of beetles. It does this by affecting their symbiotic bacteria; these contribute an essential building block (an amino acid) for the exoskeleton. Early summer should be ‘peak beetle time’ Read more...
Woodland web updates (3).
Big Garden Birdwatch. Once again the RSPB’s Big Garden Birdwatch is about to swing into action. This year , it will take place from the 29th to the 31st of this month. To take part, you just need to count the birds that you see in one hour. Details and guidance are available here : https://www.rspb.org.uk/get-involved/activities/birdwatch/everything-you-need-to-know-about-big-garden-birdwatch/ Butterflies (and moths). If you are interested in adding to your knowledge of wildlife, then the Butterfly Conservation people not only offer guidance on identifying moths Read more...
And is there honey still for tea?
Declining bee populations in Europe have caused alarm in recent years and the decline has been attributed to a multitude of factors / causes, for example :- Climate change Pesticides - especially neonicotinoids Varroa mites Viruses Now Russia is reporting mass bee deaths and major declines in their bee populations in recent months. Read more...
Insect Pollinators in decline
The science journal Nature has published the results of another insect survey, specifically of pollinating insects. The UK pollinator monitoring scheme looked at some 353 species of bees, bumblebees and hoverflies. The survey analysed 700,000+ sightings of pollinating insects over thirty years or more (1980 to 2013). The survey yielded information about the changes in the range of these different pollinators - that is the different parts of the countryside that these insects were found in. The survey did not attempt to determine actual numbers of bees etc in an area. There were “winners and losers’ in the survey but the overall picture was somewhat depressing. Read more...
The mite that kills honeybees – Varroa destructor.
The woodland’s blog has repeatedly reported on the state of honeybee populations and the phenomenon of colony collapse disorder / syndrome. Three principal factors have been held responsible for the decline in honey bee numbers : Pesticides - notably the neonicotinoids Poor nutrition Parasites. Amongst the parasites, various viruses have been associated with decline - such as deformed wing virus (DWV), sacbrood virus (SBV) and black queen cell virus (BQCV). These viruses are spread within the colonies (hives) by the activity of mites, specifically the varroa mite. It has generally been assumed that whilst the mite feeds off of a honeybee (by hitching a ride on the bee), it did no great harm. However, recent work by Samuel Ramsey et al (formerly at the University of Maryland) suggest that it is the mites’ feeding activities that are ultimately responsible for the death of the bees. Read more...