Systemic Pesticides,
The Environment and Bees

Below is a Question And Answer Session with scientist, Dr henk Tennekes.

Dr Henk Tennekes is a researcher at the Experimental Toxicology Services in Zutphen, the Netherlands.

He has combined his own research using the Druckrey–Küpfmüller equation, as well as statistical evidence to measure the impact of systemic pesticides (such as neonicotinoids).

He was one of the first scientist to bravely campaign and raise concerns regarding the impact of neonicotinoids, not only on bees, but also on birds.

Systemic pesticides are used in large quantities in the UK, in the USA and in other countries in Europe, on agricultural land, and may also be sprayed by some councils, and on some golf courses.

They are even contained in many garden pesticides, as well as some compost brands for killing vine weevils.

Neonicotinoid pesticides fall into the category of systemic pesticides.

A link to his scientific paper published in Toxicology can be found at the bottom of this page.

He has also written a book. It is well worth a read - see my review with a link to his book: (opens a new window)
A Disaster in the Making.

I contacted Dr Tennekes, and he agreed to answer some questions to be published on this website.

BuzzAboutBees: You used the Druckrey–Küpfmüller equation in your research. This sounds very complicated, so what, in simple terms, does it tell us, and why is it useful?

Dr Tennekes: The Druckrey-Küpfmüller equation tells us that very low doses or concentrations of some compounds can have devastating effects in the long run.

BuzzAboutBees: You have spoken about the ‘mobility’ and ‘persistence’ of systemic pesticides in soil. Indeed, neonicotinoids are a type of systemic pesticide, and original product data sheets published by the US Environment Protection Agency do indeed refer to these characteristics. But what, in simple terms and in practice, does this mean and why should the public be concerned?

Dr Tennekes: Soil acts as a major sink for bulk of the pesticides used in agriculture and public health programs. Pesticides may cause problems when they seep out of storage or are washed out of the soil into waterways and groundwater. The chemicals are then diffused through the environment and may affect marine and bird life. Systemic insecticides are prone to cause such problems because not only are they soluble in water and mobile in soil, they are also not easily degraded in soil and water, i.e. they persist in soil and water, and aquatic and terrestrial organisms may be chronically exposed to these substances.

BuzzAboutBees: You refer to the leaching properties of systemic pesticides, and indeed, warnings of potential ground water contamination appeared in original US EPA neonicotinoid Fact Sheets. So it would seem then, that unintended water contamination could occur without our being able to control it, or perhaps even being aware of it? Dr Tennekes: Yes

BuzzAboutBees: According to your research, is this a possibility?

Dr Tennekes: Yes

BuzzAboutBees: And if so, is this something that those responsible for waterways and human water provision (from spring and for tap water), should be concerned about?

BuzzAboutBees: It is claimed, that if correctly used, systemic pesticides are not a problem for bees and other non-target insects. What, according to your evidence, is your view of this, and can the effects of these pesticides simply be controlled by using small doses?

Dr Tennekes: No, they can’t. The damage to insects is cumulative and there may not even be a safe level of exposure. Even minute quantities will have devastating effects in the long run.

BuzzAboutBees: Not only are insects important for pollination, but birds and bats need them for food. In your research, you show that birds depending on insects for food have declined rapidly since the 1990s (and various statistics also indicate declines in bats) – of course, neonicotinoid pesticides have been available and in use since 1991. Did this decline actually accelerate significantly during that time period (in comparison with other time periods)? What kinds of percentage decreases did you observe – could you provide a few examples?

Dr Tennekes: An alarming example is the steep decline of ground-nesting birds in Saxony since 1993-1996, i.e. after the re-unification of Germany when ‘modern’ farming practices were introduced:

The decline of ground-nesting farmland bird populations (breeding pairs) in Saxony since the mid 1990s:

Species 1993-1996 2004-2007 Comment
Grey Partridge
Perdix perdix
1,500-3,000 300-400 The effects of pesticides on arthropods important in chick diet were identified as a major causal factor in the decline of the Grey Partridge
Northern Lapwing
Vanellus vanellus
900-1,600 500-800 Chicks require ground-dwelling prey such as ground beetles (Carabidae) and earthworms (Lumbricidae) on the surface
Saxicola rubetra
2,500-5,000 1,500-2,500 The decline of the Whinchat was shown to be related a decrease in the availability of nestling food affecting parents’ foraging efficiency and reproductive success
Northern Wheatear
Oenanthe oenanthe
600-1,000 350-600 Diet based chiefly on insects, also spiders, molluscs, and other small invertebrates, supplemented by berries. Normally locates prey visually, chiefly on ground or in low vegetation
Meadow Pipit
Anthus pratensis
2,500-5,000 1,500-2,500 Diet based on invertebrates, with some plant seeds in autumn and winter. Feeds almost exclusively on ground, walking at steady rate picking invertebrates from leaves and plant stems
Crested Lark
Galerida cristata
500-800 250-400 Diet is mainly based on plant material and fewer invertebrates in winter. Most food taken from on or below ground surface. Digs with blows of bill to left and right. Will take insects by aerial-pursuit and stripping wings off before eating body.
Sources (unless indicated otherwise): Anonymous (2008). Ist das Artensterben in der Agrarlandschaft noch aufzuhalten? Dokumentation der Fachtagung „Biodiversität“ der Fraktion Bündnis 90/Die Grünen im Sächsischen Landtag am 17. November 2008; Britschgi A et al (2006) Biological Conservation 130: 193-2005; Potts GR (1986). The Partridge: Pesticides, Predation and Conservation. London: Collins

BuzzAboutBees: Interestingly, some scientists believe that pesticide exposure increases susceptibility to various diseases, such as nosema in bats and bees. Do you know anything about the work of other scientists in this area, and what they are concluding?

Dr Tennekes: It has been demonstrated that the interaction between the microsporidia Nosema and a neonicotinoid (imidacloprid) significantly weakened honeybees. The conclusion is that interaction between an infectious organism and a chemical can also threaten pollinators.

BuzzAboutBees: I am concerned that the regulatory approval systems for pesticides do not take account of:

    - The cumulative effects of tiny doses of pesticide on beneficial insects over time, that may not immediately kill, but will inevitably do so;
    - The combined impact of combinations of chemicals used in the system, such as fertilizers, pesticides, weedkillers and fungicides, and how they might affect the tiny bodies of insects – from butterflies to bees and ladybirds;
    - The resulting broader impact on the wider environment of killing insects, such as the percentage declines that might be expected on various species through the food chain;
    - The uncontrollable and unknown effects, such as unintended water contamination as described above.

Whilst it may be an impractical nuisance and even impossible for commercial organisations to supply such information, nevertheless, without it, it feels like we are conducting experiments on the environment that sustains us, without knowing what the outcome might be.
What would your view be of the points above, and what changes, if any, do you think need to be made to the pesticides approval procedure?

Dr Tennekes: More attention has to be paid to chronic effects of pesticides in the environment on aquatic and terrestrial organisms. Monitoring whether or not pesticides or their degradation products leach to groundwater under actual field conditions when applied in the prescribed manner is vital. In cases where a pesticide or its degradation products leach to groundwater the monitoring results generated should provide a basis for reassessment of the substance by the regulatory authorities. Such programmes are already in place in Denmark since 1998.

BuzzAboutBees: Thank you Dr Tennekes for your time.

Link to my review of Henk Tennekes' book
Read my review of Henk's book, link to his book and scientific report.

Link to Pesticides Bibliography
Link to more studies concerning systemic pesticides and their impact on bees and the environment. Here you will also beable to download the study by Dr Tennekes that was published in Toxicologist.

Additionally, there is a report by the invertebrates conservation charity, Buglife, that summarises a number of research studies concerning neonicotinoids and Fipronil, another systemic pesticide.

More studies
More evidence looking at neonicotinoids. Summaries of some key independent scientific papers looking at the impact of these systemic pesticides.

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