Controlled Burning to combat devastating heather beetle attack on Sullington Warren

Sandgate heather beds

Did you notice in late summer that large parts of the heather on Sullington Warren were not purple with flower but a reddish brown? This was the result of a massive heather beetle infestation of this section of the Warren.

The larva of the beetle is found feeding on the leaves, stem and bark of heather plants from June through until early September. If the number of larvae are very high this can result in the heather being killed and this is what happened on parts of Sullington Warren last summer.

Charlie Cain, our National Trust Area Ranger, has developed a plan to tackle the heather beetle infestation and regenerate the heather. He has asked Sandgate Conservation Society to help him let local people know about the plan so that they understand why the heather beds are being managed in such a seemingly destructive way and what they can do to help the heather restoration.

In late summer/autumn last year the National Trust employed a contractor to cut wide strips through the most badly affected areas. The cuttings from these areas were pilled into a large heap in the hope that any adult beetle collected as part of the mowing operation would be contained and killed with the heap, to reduce the risk of a massive infestation of other parts of the site in the following year.

These mowed strips were cut in such a manner as to leave “living room carpet” sized patches of uncut dead heather stems. The National Trust intents burning off these patches, one by one, this winter before the heather comes back into active growth. They are doing them one by one to avoid the risk of the fires getting out of control and threatening the unique ecology of the rest of the site.

The National Trust feels this burning will have two advantages for the site:

1) Heather seed needs light to hit the mineral soil surface to stimulate germination. The seed is extremely fire tolerant so the seed bank within the soil will be unaffected by the burning but after the burning it will be exposed to the light to encourage good germination rates in the spring.

2) The remaining heather beetle population in the affected areas will, at this time of year, be an adult beetle hibernating under the moss layer where the larva lived and fed. Burning these areas has the potential to reduce the number of adults that will survive the winter and thereby reduce the risk to the remaining heather on the site next summer.

The beetles come out of hibernation in mid-February to March when the mean temperature is above 9°C, so it is important that this burning operation is carried out before then, if possible, to have the best chance of controlling the heather beetle population. Studies have also shown that regeneration from burned heather plant is much greater if the operation takes place before the plants try to flourish in the spring.

If you enter the Warren from the Heather Way gate and walk straight on towards The Green the affected area is to you left and this is where the burning will happen.

The area to your right of this was attacked by heather beetle in the same way eight or nine years ago. The National Trust have been doing lots of bits of work over the last six or seven years to re-establish carpets of heather as opposed to the wavy hair grass and Festuca carpets that colonised this area after that infestation. The restoration of this area has mainly been the manual removal of moss, carried out by volunteers, to expose dormant heather seeds to light to stimulate heather seed germination and regrowth. The hope is that the burning operation will re-establish a heather carpet much more quickly over the areas that were killed last summer than has been achieved on this section, and with less back-breaking effort!

What you can do to help?
The photograph shows what Sullington Warren looked like in August 2010 before the heather beetle infestation. This is what the National Trust is aiming to get the heather beds looking like again. All of us who use and enjoy Sullington Warren can help.

Please do not walk across the heather beds or encourage your dogs to run into them. There are plenty of obvious paths around the heather beds, there are none across them. Walking across the heather can damage the vegetation, including recovering heather plants, disturb the wildlife (many invertebrates and reptiles, including adders live there – there is also the potential for ground-nesting birds in the spring if the areas were left undisturbed) and cause soil erosion.

Also, there is some evidence that increased soil fertility is exacerbating the heather beetle problem by producing heather growth that the heather beetle larvae finds more nutritious. Increased nitrogen in the soil also encourages vegetation that competes with heather such as grasses and brambles. The major source of excessive nitrogen in the soils at Sullington Warren is from dog fouling. It is really important that dog waste on Sullington Warren is disposed of properly one of the dog waste bins provided.

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