The problem with Heather Beetles

The Heather Beetle (Lochmaea suturalis) is a native Chrysomelid leaf beetle which feeds almost exclusively on heather (Calluna vulgaris). It is common in areas whether heather grows from the south of England to Orkney in the north (Duff 2016).

Heather beetle populations are well known to fluctuate greatly from low numbers which have little over impact on heather plants to very high numbers which can lead to the widespread defoliation of heather and can cause its death.

Heather Beetle damage on Ryders Hill March 2016

Heather beetle outbreaks have historically been problematic for grouse moor owners and the issue of heather beetle and its control has been championed by the Heather Trust who have produced a short document on the species (Heather Trust undated).

In addition the Heather Trust commissioned a literature review of the species (Rosenburgh & Marrs 2010) which summarises the ecology of the beetle, its impact as a pest and strategies for control. This work has been updated (Gillingham et al 2015a and 2015b) and published as Natural England Evidence Reviews on its ecology and its management.

These reviews state the following regarding heather beetle outbreaks:-

  • ‘Considerable damage to heather can occur with complete death in the worst cases’.
  • ‘Large scale vegetation change can follow’ (heather outcompeted by invasive grass species).
  • ‘The occurrence and severity of heather beetle attacks appears to be made worse by increased levels of nitrogen in the soil and plant tissues, which has been blamed on high nitrogen pollutant inputs from the atmosphere in recent years’.
  • ‘The high nitrogen in the leaves provides the beetles with more high quality food to consume’
  • ‘Climate change is expected to lead to increased winter survival of heather beetles’

On Exmoor heather beetle is considered a major problem, and the National Park Authority report that outbreaks are common and are spreading from the south to the north of Park. They also suggest that in areas where Purple Moor Grass (Molinia caerulea) is absent the heather plants recover fully and rapidly but where Molinia is present this quickly swamps the heather and replaces it (ENPA 2015).

I have written before about the loss of heather that had occurred on the National Trust’s land in the Upper Plym valley on Dartmoor (see here). In 1995 there was a serious outbreak of heather beetle which killed off the heather in the area known as Hen Tor Fields. At the time it was assumed that overgrazing was the cause although no increase in stocking levels had taken place for a number of years.  In this specific instance the heathland communities (H12 Calluna vulgaris-Vaccinium myrtillus) were replaced by upland grass communities (U4 Festuca ovina-Agrostis capillaris-Galium saxatile) which do not naturally contain Molinia. On the wet heaths of the Upper Plym Estate there were numerous other outbreaks on heather beetle during the 1990s and 2000s (Helen Radmore NT tenant pers comm) and in these habitats Molinia now dominates (my observations).

There has been no systematic survey of heather beetle on Dartmoor and Goodfellow et al (1997) only briefly mention it “Outbreaks of heather beetle cause local declines in heather”, however my recent observations on the moor suggest that heather beetle damage is very widespread and extensive.

Heather Beetle damage on Ryders Hill – March 2016

I would be very interested to hear from anyone with information about heather beetles on Dartmoor in recent years – it is an issue which is begging for more research.

Duff A.G. (2016) Beetles of Britain and Ireland. Volume 4 Cerambycidae to Curculionidae. A.G. Duff (Publishing) West Runton.
ENPA (2015) Exmoor Swaling Review 2014/15. Seminar Notes ENPA. Dulverton.
Gillingham P., Diaz A., Stillman R. & Pinder A.C. (2015a) A desk review of the ecology of the heather beetle. Natural England Evidence Review, Number 008.
Gillingham P., Diaz A., Stillman R. & Pinder A.C. (2015b) Desk review of burning and other management options for the control for heather beetle. Natural England Evidence Review, Number 009.
Goodfellow S., Wolton R. & Baldock N. (1997) The Nature of Dartmoor: a biodiversity profile. English Nature / Dartmoor National Park Authority publication.
Heather Trust (undated) Heather Beetle. Download from Heather Trust Website
Rosenburgh A. & Marrs R. (2010) The Heather Beetle: a review. Report to the Heather Trust.

8 thoughts on “The problem with Heather Beetles

  1. Hi Adrian,
    Have you visited Geoff Eyre farm where he systematically cold burns small areas of old or unhealthy heather on Howden Moor. The patchwork of heather of different ages is attractive. He has game keepers but the wildlife birds and hares are astonishing in number. He has said in the past he would like to show you round! Fairfax

    • Fairfax – I definitely intend to visit Geoff Eyre – so many people I meet talk about him. Before I meet him I need to get my research methodology approved by the University so it probably won’t be until late this year / next year.

      Best wishes

  2. That’s good news and young grouse will be taking off! This article from Edmund Marriage comments on the different management systems. Fairfax

    The RSPB’s political lobbying, a major influence on Minister Elliot Morley and Government rural policy, calls for their own track record on moorland management to be put under the spotlight.
    Fortunately we have a good example of the consequences of RSPB management at their reserve at Carn Gafalit in Mid Wales following their acquisition of the SSSI product of generations of good grazing management.

    1. 13 graziers were told to stop traditional patchwork burning of the heather, leading to loss of control of the ideal habitat.
    2. Loss of ideal habitat has curtailed traditional grazing management of cattle and sheep, with the loss of 10 graziers through lack of incentive. The subsequent loss of dung and urine has reduced the insect population and soil quality.
    3. The resulting under-grazing and lack of scrub control has led to one large accidental fire, probably started by walkers. Heather has taken 6 to 7 years to partially recover from attempts at control by flailing, being smothered by pulp. Where burnt, regeneration took place in 3 years.
    4. Out of control bracken and 4 feet high heather, causes the remaining 3 graziers lose their sheep and even their cattle, complicating management and veterinary treatments.
    5. Ticks and heather beetle now present serious uncontrolled problems.
    6. There is little effective vermin control, a five-fold increase in the local badger population, and so much general predation that prey species numbers have collapsed.
    7. 30 to 40 grouse would have been seen regularly, now there appear to be none.
    8. Hen Harriers were released into this area and have failed to survive the low food supplies, excessive predation and management neglect.
    9. There has been no attempt to discuss management with the graziers despite requests.

  3. Adrian, many thanks for taking up the case of Heather Beetle. As you are aware, it has been a cause of concern to The Heather Trust for many years and the potential for this beetle to cause havoc in heather in much under-rated. I support the view that heather beetle is one of the drivers of change from heather dominance to purple moor-grass dominance, and the associated loss in diversity of plants and grazing options.

    We have been tracking outbreaks of heather beetle for over seven years and publish the results on the heather beetle section of our website. I inspected the recent outbreak on Exmoor when it was at its height, but I would be delighted to have some more reports from Dartmoor to help us complete the picture. Anyone with information is asked to send it to us on the survey form, but information in any form forwarded by any means will always be welcome.

  4. (Fairfax ) Comment from Geoff Eyre

    Yes it would be good to see Adrian, he is at least interested in moorland problems and I can identify with his observations, huge areas in Scotland saw heather disappear through heather beetle attack and I can now see historic wrong management (even some kneejerk burning at the wrong time ) followed leading to a graminoid invasion ,mainly molinia as beetle prefers these damper sites and future increase in sphagnum (rewetting flavour) will actually see more beetle invasions.

    With todays agricultural technology there should be no reason such wide scale loss of heath through beetle attack should be seen again but those in charge of the environment should be open to agricultural methods and maybe a short period of controlled grazing if needed. It is sortable but my anecdotal methods are not liked even trial plots scorned on as the “upland” now seems to be untouchable by the hand of man, yet all designations such as National Parks ESA s SSSIs SPA have all been acknowledged as man made and enjoyed by the public .

    Edmunds quoted “official grazing view was technically correct ” given the old way was to burn off dead beetled heather often mixed with molinia and in many cases the heather was old and could not recover from rootstock so had to come back from seed, sheep find seedling heather very juicy as molinia digestibility declines so they can eventually destroy heath in the habitat, where it all went wrong was the fact the molinia was not controlled and this inhibited mass heather seedlings return (as seen returning on burnt monoculture heather beds) , my herbicide approach works and allows numerous heather seedling (already in the seed bed) to flourish even if sheep control some growth in the early years.I have increased heather cover when I am allowed to control molinia/nardus .

    Regards Geoff

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