Heather beetle damage on Dartmoor 2019

I have been very surprised how much Heather Beetle damage there is on Dartmoor this year. The Heather Beetle larvae hatch in June and then feed on the young leaves and shoots. As a result the affected parts of the heather plant turn orange brown.

Heather Beetle damage. It is very characteristic and eye catching.

Last week I walked from Rowtor on Okehampton Common up the military road to Observation Post 15 and then down to Ockerton Court. All the way along the track there are signs of extensive damage to the heather plants – I would estimate that over 90% of plants are affected.

Work carried out in the north of England and in Scotland suggest that the larvae are active until the end of August when they drop down into the litter and pupate into adult beetles. Despite three separate searches on Okehampton Common, the Forest of Dartmoor and Headland Warren Common I only managed to find three larvae and one adult beetle.

Here is a Heather Beetle larvae on Okehampton Common eating the few remaining green leaves of the plant.

I suspect that the absence of larvae and adults during my searches in the first week of August means that the larvae have already dropped into the litter and are beginning to pupate – as a result larvae and adults are not visible. However the very extensive areas of damaged heather indicates that they have been very active in June and July.

It is possible for the heather to recover from this attack and I will be monitoring it to see if it does. However parts or all of the heather plant can be killed. When this happens the shoots turn from orange brown to grey.

This is mature heather at Ockerton Court which has been killed by Heather Beetle

In this image the areas of dead heather (darker brown bits) are being over run by Purple Moor Grass (Molinia caerulea) – the bright green shoots of this year’s growth and the light brown leaves from last year. Molinia is unable to replace heather whilst the heather is alive but can and does do so when it is dead.

Heather Beetle is a seriously under-recorded species on Dartmoor – the National Biodiversity Network database has just one record and the is from Fingle Woods and not from the high moor!

There is clearly a need to gather more records ….

There is anecdotal evidence nationally that Heather Beetle attacks are getting worse and it has been suggested (based on research from the Netherlands) that the severity and frequency of Heather Beetle outbreaks is linked to the levels of atmospheric pollution – particularly nitrogen levels.

Dartmoor receives high levels of nitrogen deposition as a result of its high rainfall – Natural England have reported that Dartmoor receives 24kg / ha / annum of nitrogen (as NOx) which is damaging the blanket bog and mires. This high level of nitrogen deposition may also be responsible for the high levels of Heather Beetle damage.

Heather Beetles are a natural part of the moorland wildlife community and historically damage to heather was limited except in the ‘outbreak’ years. Last year when I was walking the Commons in July I also noticed extensive areas of affected heather – at this point in time heavy attacks appear to be frequent – maybe even annual.

There are implications for wildlife, conservation and hill-farming as a result of these serious Heather Beetle attacks.

  1. The heather plants themselves are either killed or remain stunted
  2. The species of wildlife which feed on heather shoots are also impacted – this includes moth species such as the Emperor Moth and the Fox Moth, whose hairy caterpillars are important prey items for one of Dartmoor’s iconic and successful birds – the cuckoo.
  3. Heather has long been a conservation indicator for the condition of Dartmoor’s Commons and historically grazing levels were reduced significantly to reduce overgrazing pressures to conserve heather.
  4. Heather is also a winter food for sheep on the Commons, if the amount of heather generally is significantly reduced as a result of Heather Beetle attacks it put pressure of the remaining plants that have survived.

Ironically it is thought that the severity and frequency of Heather Beetle attacks has increased because the nitrogen has made the young shoots and leaves more nutritious, it is also reported that sheep preferentially graze the new shoots too for the same reason.

There is a dearth of information on Heather Beetle issues on Dartmoor but from my own observations this year and last it is a potentially serious and widespread problem. However it would also appear that the problem is not universal across the moor. I searched for it in the heather stands around the Warren House Inn  and found Heather Beetle attacks to be minor Рperhaps this level of damage is the natural level Рwhereas the levels seen on Okehampton Common, the north part of the Forest and on Headland Warren Common are the outbreak levels.

It seems to me that there is a clear need to better understand the Heather Beetle situation on Dartmoor, this would be in the interests of Natural England, the Dartmoor National Park Authority and the Dartmoor Commoners Council. The time to survey for the impacts of Heather Beetle is July and August. Maybe a bit of ‘Citizen Science’ could come to the rescue?

I would also be interested to hear from people who have found the characteristic orange brown stands of heather this year on Dartmoor.

I’ve written before about Heather Beetles and this link takes you to my blog which contains further information and some references you can download.

The wildfire site at Gidleigh

I’ve been back to Gidleigh Common today to see what the wildfire area (April 2018) looks like this spring.

The wildfire area is the green bit. The brown bits are the areas of ungrazed Molinia (Purple Moor Grass) which were not affected by the fire. The rocks on the skyline top right are Watern Tor.

Just to the south is the rest of Gidleigh Common, part of Chagford Common and the new takes up to Sittaford Tor. As you can see the majority of it is dominated by Molinia.

Amongst the green bits were five different herds of cattle – all Galloways or Belted Galloways – the black dots in the picture. The cattle were only grazing in the fire area and none in the Molinia. These cattle are not Gidleigh Common cattle – they have been drawn in from elsewhere – mainly the Forest of Dartmoor. The cattle love the new sweet grass that grows after a fire. That is good for the burnt area but bad for the unburnt areas which simply become more overgrown. It looks there will be no grazing this year (again) in places like the flanks of Hangingstone Hill (see yesterday’s blog – here).

The Gidleigh Galloways (and some ponies) were grazing to the north on an area that was burnt 7 years ago but has been grazed every year since. Again the areas of Molinia to the right are untouched.

Too much Molinia and not enough cattle ….

Gidleigh Commoners are currently trialling winter grazing of Galloways – they won’t eat much of the Molinia in the winter but they do trample it down. The winter feeding of the cattle is being done sympathetically by good shepherding and there appears to be no detrimental effects.

What for the future?

Some hill-farmers advocate new light burns each year in adjacent Molinia patches to lure the cattle onto the new growth. But without more cattle (which hill-farm economics does not really encourage) it is hard to see how the Molinia problem can be ‘solved’ on the Home Commons such as Gidleigh – let alone the massive Forest of Dartmoor Common which is now largely a Molinia jungle.

This whole topic is down for debate at the Dartmoor Commoners Council meeting this Wednesday …..should be interesting but I bet there won’t be a consensus.

 

 

A ray of hope in the Forest?

I went for a long walk on Dartmoor yesterday up into the Forest of Dartmoor. For those of you not familiar with the area it is dominated these day by Molinia – Purple Moor grass. Walking is only comfortable if you follow defined tracks as the vegetation is now very overgrown and under grazed.

Here is the view from the flanks over Hangingstone Hill looking over towards Steeperton Tor and the Belstone Ridge. The light coloured vegetation is Molinia and the darker patches in the middle distance are areas of heather (Calluna vulgaris).

Here is a close up version of the same habitat. As you can see the vegetation is ungrazed. Historically this area would have been grazed and summer grazing by cattle along with their winter trampling would have controlled the growth.

I have been to this area many times over the past 18 months and have never seen any cattle up here, only a handful of sheep and a herd of ponies. The ponies too can make a difference but their numbers are much reduced and there are now few incentives for hill-farmers to increase their pony numbers.

However there is an area between Okement Hill and Hangingstone Hill where there is still an active lear (an area where stock have been shepherded to remain and graze). Here the area has been grazed in the summer and the Molinia growth has been eaten. In addition the heather is thriving.

If only this could be replicated over the thousands of acres of ungrazed Molinia on the moor but sadly the shepherding practices and numbers of cattle required currently aren’t in place and moorland economics make such a prospect remote. Something for the new Environmental Land Management Schemes to address?

The web of life – badgers, bees and bee-flies

So here is a badger foraging in my garden

It digs holes and scrapes in its search for food

And then …. a Tawny Mining Bee (Andrena fulva) excavates her nest in one of the badger scrapes – the entrance looks like a little volcano.

And this is the female Tawny Mining Bee who excavated this nest

And here she is emerging from her nest

Lurking nearby is the Dark Bordered Bee-fly (Bombylious major) which is a parasitoid i.e. it lays it egg in the burrow of the Tawny Mining Bee (and other species) – its larvae then eat the larvae of the bee

Also lurking in the nearby flower bed is Gooden’s Nomad Bee (Nomada goodeniana) – another parasitoid species, but this a bee not a fly and fortunately for the Tawny Mining Bee it lays its eggs in the nests of other Mining Bee species

And all of this happening in my back garden in Exeter over the past couple of weeks …..

A walk around the south moor

I’ve been out on the south moor today with Rob Steemson, the DNPA’s longest serving Ranger, great company and glorious weather. We were reccying a few sites, looking at the vegetation condition and looking at a few places suffering from erosion.

We started near Peat Cot and headed down the recently restored ‘yellow brick road’ to Nunn’s Cross and onto the Eylesbarrow Tin Mine and then over Plym Steps and onto the Abbott’s Way and up to Broad Rock.

This is a boundary marker stone between Willing Walls and Hentor Common (owned by the National Trust) and the Forest of Dartmoor.

Plenty of frog’s spawn around

Down to the very impressive Erme Pits

We then followed the Blacklane Brook up to Duck’s Pool (where the mire is soon to be restored using DEFRA funding)

This is the location of the second ever ‘Letterbox’ on Dartmoor (the first being Cranmere Pool)

There is a memorial plaque there in honour of William Crossing

And the box containing the letter boxing paraphernalia tells the story

Duck’s Pool comes complete with ducks …..

Then north up the peat pass to Fox Tor and Fox Tor Mire beyond. The smoke in the middle distance is from a bit of swaling taking place in a New Take near to the West Dart.

Here’s the route – it’s about 9 miles – much of it is pretty remote ….. so ….. make sure you are suitably equipped if you want to try it out.

A January afternoon on the high moor

Just for a change I went up onto Dartmoor this afternoon!

I went in search of the herd of Highland cattle which inhabit the Commons between the Warren House Inn, Headland Warren and Hameldown, spent a lot of time searching but to no avail! Facebook tells me they are still there …. somewhere!

Nevertheless found plenty of other things to look at and photograph – here are a few of my pictures.

A Swaledale near Headland Warren

Scotties near Headland Warren

Down the Challacombe Valley

On the drove up to Great Mis Tor

South Devons at a ring-feeder on the in-bye near Postbridge

A new perspective on the Postbridge clapper bridge

Scotch Blackface sheep under a busy Haytor

Saddle Tor via a Lensball

Take 2

Sunset at Saddle Tor

The sheep i.e. the ewes are now back on the Commons having been tupped (mated) by the rams – the Dartmoor farming year keeps turning.