Interesting piece by Guy Watson of Riverford Organic Farmers
Amazing day’s weather in Exeter yesterday – it seemed like all four seasons had been wrapped into one day. Heavy rain, hail, 18 degree sunshine and wind. During the sunny bits it seemed like spring had arrived – I saw my first bee flies of the year along with hoverflies, a peacock butterflies and the solitary bee – the Hairy-footed Flower Bee.
It has a very interesting life cycle which I have written about before – see here – it only flies when temperatures are above 17 degrees.This is the Drone Fly (Eristalis tenax) – a hover fly which is mimicking a honey bee. Hoverflies cannot sting but work on the assumption that you think they can!
If you have got a garden it is possible/probable that all of these species will be living in it – on a sunny day have a look to see who you are sharing your garden with.
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 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.
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. http://www.exmoor-nationalpark.gov.uk/__data/assets/pdf_file/0011/583454/Exmoor-Swaling-Review-2014-15.pdf
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. http://publications.naturalengland.org.uk/publication/6386866406293504
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. http://publications.naturalengland.org.uk/publication/4817807814426624
Goodfellow S., Wolton R. & Baldock N. (1997) The Nature of Dartmoor: a biodiversity profile. English Nature / Dartmoor National Park Authority publication. http://www.dartmoor.gov.uk/__data/assets/pdf_file/0014/42701/au-natureodp2.pdf
Heather Trust (undated) Heather Beetle. Download from Heather Trust Website http://media.wix.com/ugd/fdc287_2b9ec8fa073d4ca38baf4a754d7a77f4.pdf
Rosenburgh A. & Marrs R. (2010) The Heather Beetle: a review. Report to the Heather Trust. http://media.wix.com/ugd/111722_4370d9fb976442b2af6e678aa83c3663.pdf
I was up on the Moor over the weekend helping look after 9 teams of 10 Tors participants from the National Trust Wild Tribe and Torquay Boys Grammar School. Saturday saw some of the worst and most challenging conditions I have witnessed on Dartmoor – persistent driving rain, a strong wind and very poor visibility. As a result – very few photographs …..
This is a photo of Red Lake tip taken in 2015 (it is the conical man made peak in the middle ground) – on Saturday we could only see it when we were 200m from it – a day of navigation by compass – which Pete did very expertly all day.
We eventually saw all seven groups through by 5pm and then started on our 90 minute walk back to our O Brook campsite – all the teams were in camp by 7pm
Very challenging conditions – well done to all the young people who took part over the weekend – if you can walk and navigate in those conditions you have cracked it!
Dartmoor was character building over the weekend and undoubtedly the moor build some new characters.
I’ve just seen the latest Forestry Commission data on Ash Dieback – a huge increase in the incidence of breakouts in Devon – must admit I’ve yet to see a case anywhere in the UK but this is worrying.
The national picture care of the Forestry Commission
The FC have also produced two really useful videos to help you ID ash dieback
The numbers of moths in my trap are beginning to build up with the milder weather.
This is a Chestnut – lovely orangey colour and distinctive black marks