I wrote this article below in June 2013……Update.. June 2014 See this video here with Prof. Dave Goulson and other scientists who are studying neonicotinoids affects as part of the Task Force on Systemic Pesticides. They do not make their living as scientists working for chemical/pesticide manufacturers!!
Earthworms as predators of soil microbes
Food for thought?
It is a well established fact that earthworms consume organic matter and convert it into soil. Many people may not be aware that earthworms swallow organic matter as it provides them with micro organisms such protozoa, rotifers, nematodes, bacteria, fungi for most of their nutrient requirements. In other words, they are predators of the soil microbes who are themselves consuming the organic matter in the soil! The organic matter comes from the dead vegetation e.g. stalks, leaves and roots. More recently, it has been found that the earthworm, Lumbricus terrestris, the large garden earthworm seen on your lawns, under certain circumstances, may also swallow plant seeds, bury them and can disperse them. Under certain circumstances, it will also feed upon seeds and seedlings. In the case of vermicomposters, the microbes are found on the waste cooked and uncooked food waste put into wormeries, such as tea leaves, toilet rolls, potato peelings, cereals, horse manure, etc., as consumed by the epigeic litter species earthworm, Eisenia fetida.
Root zone (Rhizosphere)
As roots grow in the soil, besides chemicals from cell leakages and cell wounding, (root exudates) of more interest to microbes that consume organic matter are the tiny roots hairs, fragments and shards of roots, left in the soil. Such deposits are collectively known ‘rhizodeposition’. The immediate area around plant roots is known as the rhizosphere, ‘ the zone in soil which is influenced by the physical, chemical and biological processes of plant roots’. It is a soil food web. They are known as ‘hot spots’ for microbial activity and can have 50 times more microbial activity than in the bulk of the soil. Hence earthworms are attracted to them. Have you ever noticed pulling up a plant and finding an earthworm entangled in the soil and roots? This is the reason why. Away from the root zone, the area where the bulk of the soil is, plant waste and organic matter are only at a low concentration, hence a poorer environment for many soil microbes and earthworms.
Earthworms as soil bioindicators
Earthworms have been used to monitor and test the health of soil ecosystems for chemicals, heavy metals, radioactivity and environmental contamination of hazardous waste sites. Being such ideal candidates for testing soils, Edwards was contracted some years ago by the EEC, to develop a standardised earthworm toxicity laboratory test for testing soils.
Earthworms as bioaccumulators
Some pesticides e.g. DDT, are known to accumulate inside of earthworms, with it being of little risk to them. They can also accumulate heavy metals from polluted soils and other media. They probably can accumulate much higher levels of heavy metals than most other soil animals. Can they accumulate neonicotinoids as well?
Non targeted species
Research into the lethal/sub lethal effects of pesticides on non targeted species is well documented, both in scientific journals e.g. DDT with the decline of sparrowhawks and decline of robins in the USA. In some UK orchards, there was a decline of blackbirds, mistle thrushes and song thrushes, when they ate DDT contaminated earthworms. The DDT accumulated in the birds fat deposits resulting in their deaths. Then of course there is Rachel Carson’s ‘Silent Spring’. Now we have recent research re similar outcomes from neonicotinoids, (see below).
Are modern pesticides any different? More recent research by Goulson on the effects of neonicotinoids, found that consumption of small numbers of seeds with neonicotinoids offered a route to direct mortality in birds and mammals.
Earthworms as prey items
Numerous bird species, e.g. robins, song thrushes, blackbirds, mammal e.g. moles, badgers, foxes, amphibians, e.g. frogs, newts, certain predatory beetles. On another level, foxes predate upon birds which themselves may have consumed contaminated earthworms. A more complete list can be found here. Other consumers of organic matter and which are preyed upon can include slugs, snails, woodlice and millipedes. The importance of soil, mulches and its benefits to wildlife are very under rated.
How do neonicotinoids work?
Developed in the 1980′s and introduced in the 1990‘s, they were supposed to be more efficient than the older generation of insecticides. They contain synthetic nicotine substitutes. They are neurotoxins, with a high toxicity to most arthropods (no backbone and with an exoskeleton). Numerous species live in the soil and on the soil surface. It paralyses them and affects their nervous systems after coming into direct contact or by oral contact, e.g. chewing or sucking plant juices.
Protection from root to fruit
Being a systemic chemical it travels through (translocation) all the plant tissues, protecting all of the plant and crop, from seed to root to fruit. Being systemic they are also found in nectar and pollen of treated crops. They are used as an insurance policy against pests, whether they are present or not. The philosophy of Integrated Pest Management, IPM, which encourages the use of non toxic options and monitoring before resorting to pesticides as a last resort need no longer practiced, as the pest number do not reach the threshold of economic damage. It will be interesting to see what happens from 1st Jan 2014 when the EU Directive 2009/128/EC makes IPM obligatory in crop protection.
Neonicotinoids are flexible in their applications. They can be sprayed, applied as a soil drench, used in irrigation waters, injected into tree trunks or as now, widely applied as a seed dressing. As a seed dressing they could be used in much lower quantities and promised to be less polluting to the environment and as the treatment is found throughout the whole plant requires minimal action by the farmer, eliminating crop spraying and protects areas of the plant difficult to reach for spray application. They are now the most widely used insecticides in the world, licensed in 120 countries and have a global market value of $2.6 billion. Crops include oilseed rape, cereals, beets, potatoes, tomatoes, squash, sunflowers and some soft fruits. They are used in parks and gardens. You can buy them in garden centres, although more enlightened ones have taken them from the shelves.
Non agricultural use
Dog and cat owners may not know that they could be using imidacloprid, a neonicotinoid, on their pets as a flea treatment and it is also used for other pests in cattle. This is not affected by the EU ban on neonicotinoids, see below.
Unforeseen consequences – affects on bees
Whilst sowing the dressed seeds, a small proportion of the pesticide is lost as dust and this dust has been found to cause direct mortality in honeybees who came into direct contact with it, unfortunate enough to be flying nearby, a lethal effect. The dust is deposited on field margins, often planted up with wildlife friendly flowers nowadays to encourage wildlife! Sub lethal effects,( too small a dose to kill) as a result of oral contact in bees, include effects on reproduction, foraging behaviour, memory/learning abilities, communication abilities, (e.g. bee waggle dance)and overwintering success. It also affects their mobility by inducing symptoms such as knockdown, trembling, uncoordinated movements, hyperactivity and tremors.
Neonicotinoids have been found in pollen collected by bees, bees wax, honey and the bees themselves. Honey is used by honey bees to feed themselves through the winter, if it contains neonicotinoids they will be exposed to them for a long period as they consume them. Some solitary bees use masticated leaves to construct their nests, others use mud and others live inside wood borings. What are effects on them are there when they come into contact with neonicotinoid contaminated tissue? What effects does it have on honey, solitary and bumblebee larvae?
Persistence of neonicotinoids in soils
Typically, more than 90% of the active ingredient enters the soil, only a tiny portion, between 1.6% and 20%, of the pesticide used as a seed dressing is absorbed by the plant. Where does the majority go then? In Goulson’s review of the insecticides, he states that they persist and accumulate in soils and given their long life and potential for accumulation in the soil, it is highly likely, most arable soils may contain variable amounts of neonicotinoids. Evidence suggests that neonicotinoids remain toxic in plant tissues longer than other insecticides, for more than a year. Even untreated plants may take up residues still present in the soil from previous applications.
Persistence in water and sediment
Being water soluble they leach into our waterways. Many of the environmentally persistent chemicals found in freshwaters become associated with particulate material which eventually settles to the bottom forming sediment. Leaching of pesticides is one of the main mechanisms responsible for the contamination of groundwater and surface water. Like soil, the sediment can act as a sink for a variety of compounds and chemicals. Like soil numerous invertebrates live in the sediment. Like soil numerous plants grow in it and as on the land, these plants are eaten by numerous species and plant eaters form the diet of many aquatic predators. Like soil, freshwater sediments have worms, (aquatic worms), consuming organic matter, such as tubifex and lumbriculus variegatus.
Do neonicotinoids affect other wildlife – opening a can of worms?
Most of the research into neonicotinoids has focused on honey bees and to a lesser extent, bumblebee and solitary bees. Bees pollinate trees and bushes bearing wild berries upon which so many wild birds and mammals in the UK depend upon. What about butterflies, moths, wasps, beetles and hoverflies, all pollinators that can come into contact with contaminated plants?
Do neonicotinoids affect soil microbes, earthworms or their predators or other wildlife? Some pesticides have been shown to kill earthworms, (and honeybees) unintentionally, e.g. carbaryl, (Bhopal disaster). Fewer earthworms can result in adverse effects on soil fertility and may influence crop yields. Earthworms maintain soil structure and fertility, improve soil aeration, improve soil health, improve drainage and water holding capacity.
There is potential earthworms to consume some seeds and for seed eating mammals or birds to consume seeds left on the soil surface, such as an accidental spillage when transporting seeds, when loading hoppers etc., or when left on top of the soil. Many farmland birds eat seeds. Many are in decline. Will eating the neonicotinoid coated seeds harm or affect them in any way? Goulson states that a grey partridge would need to eat as few as 5 coated seeds to receive a lethal dose.
Water based wildlife
Recent peer reviewed research from the Netherlands, about affects of neonicotinoids leaching into water found non target wildlife, such as mayflies, midges and molluscs were killed. The researchers found 70% less invertebrate species and far fewer individuals of each species were found in neonicotinoid polluted waters compared to clean water. The neonicotinoids adversely affected the flying insects that had a larval stage in water stating that the pollution could have an a knock on effect of birds, such as swallows, that rely upon flying insects for food.
UK Government response
There has been petitions signed by millions to ban these chemicals and in further support 80,000 emails sent to Owen Paterson, the Environment Secretary, which he described as a cyber attack. This was a huge public response against the use of these pesticides. What did the UK Government do? Patterson, wrote a letter to Syngenta, (the chemical giant which manufactures thiametoxam, a banned neonicotinoid!) stating that ” we firmly believe that the proper approach is to base a decision to act on a full assessment of all the scientific evidence”. They abstained the first vote, then they (and Syngenta) continued in secret lobbying to stop the ban, eventually voting NO refusing to support the proposed EU ban, supported by European Food Safety Authority. They justified their actions by arguing that the research, undertaken by Defra scientists showing that neonicotinoids did not harm honey bees (research funded by Syngenta) nor harm bumblebees in the field. To be frank, both were junk research. How embarrassing that our UK Government should present non peer reviewed scientific research as ‘evidence’ to other EU countries for the case not to ban neonicotinoids. I am absolutely disgusted by this. Thankfully, the EU did restrict the use of Bayer’s imidacloprid and clothianidin along with Syngenta’s thiamethoxam as a seed dressing and foliar treatment on bee attractive plants and cereals, but only for 2 years, starting 31 December 2013. What happens during and after the restriction? The pesticides could still be in the soils and water….
Top UK bee scientist leaves Defra for….. Syngenta
A key government scientist whose (non peer reviewed) research was used by UK ministers to argue against an EU ban on the pesticides has resigned. She has joined Syngenta, “Government policy should be informed by unbiased and disinterested scientific research”, stated Joan Walley MP, chair of the environmental audit committee. Syngenta also produce and sell live bumblebee colonies for pollination of crops through a subsidiary company Syngenta Bioline. And yes Syngenta do spend some money on flower seeds to boost bee numbers on commercial farms with Operation Pollinator!
Safe for wildlife?
Will decomposers of neonicotinoid tainted vegetable matter be affected in any way? What are the potential repercussions of a cocktail of other chemicals when combined with neonicotinoids? Are neonicotinoids the new DDT? Why do we ever need to ask this question anyway? Surely these chemicals have been proven safe to all non targeted wildlife before their use? More research is need to establish potential affects on all wildlife and the interactions between other chemicals when mixed with neonicotinoids. I just want to eat safe food, see wildlife! and hear the sound of bees buzzing from flower to flower, which to me, epitomises summer. Banning some of them for 2 years may not stop the decline of bees, it sure has highlighted their plight. As would eradicating varroa mites, which only affects honey bees and no doubt is another factor which has brought about their decline. Its the wild bees many people are forgetting!
Update. Since writing this article Syngenta and Bayer, the chemical giants that produce banned neonicotinoids making them billions of dollars, have filed filed legal challenges against the two year ban. They claim that according to EU guidelines approved products can only be banned if there is new evidence of the negative effects. However, since they were approved some years ago, exactly that has been found. Even if they do not win their case, this could delay the ban for months…..
“All my articles and videos, available free, are funded by my teaching and sales of award winning bumblebee nest boxes, solitary bee boxes, and wormeries. Please help by spreading the word and forwarding this link to your friends and colleagues. http://nurturing-nature.co.uk Thank you” George Pilkington
For more information and to help save bumblebees join the Bumblebee Conservation Trust.
Thanks to the Guardian’s George Monbiot for reading my article and taking it to a wider audience…. “Neonicotinoids are the new DDT killing the natural world”
Refs: Besides the highlighted links, my own observations and photographs;
Anon EU Directive 2009/128/EC
Blacquiere. T. et al (2012), “Neonicotinoids in bees: a review on concentrations, side effects and risk assessment” Ecotoxicology 21(4): 973-992
Eisenhauer, N. et al (2010), “Earthworms as seedling predators: Importance of seeds and seedlings for earthworm nutrition”, Soil Biology & Biochemistry, 42 p 1245-1252
Goulson. D. (2013) “An overview of the environmental risks posed by neonicotinoid insecticides, ” Journal of Applied Ecology
Hopwood. J. et al (2012)”Are Neonicotinoids Killing Bees?”, The Xerces Society for Invertebrate Conservation
Jeffery. S. et al (2010) “ European Atlas of Soil Biodiversity”, European Commission, Luxembourg
Rathore. H. S. et al (2012), ” Pesticides: Evaluation of Environmental Pollution” CRC Press
With thanks to Roy & Marie for the Robin, blackbird and song thrush photos. See more of their lovely photographs here