The Beetles Go Downstairs

Heather beetle larvae in pupal stages
Heather beetle larvae in pupal stages

Worth mentioning that the heather beetle attack on the Chayne has taken a new angle. All of the hungry larvae suddenly vanished about three or four days ago, leaving a surprising amount of dead and dying heather in their wake. The little area of heather has been so full of grubs for the past month that their absence is very conspicuous, and I decided to try and dig down to find where they had gone. It is fairly well known that heather beetle larvae pupate in the ground, but I had no idea where to start looking, given that “ground” can mean anything from under the leaf litter right down into the soil.

Scratching around amongst some sedges next to the damaged heather, I lifted several layers of litter and rotten moss until I was down to the blaeberry roots. There was no sign of any pupating beetle larvae at all, and I almost gave up the search. Then I spotted badly damaged heather growing through a pad of moss that was around five inches deep. Pulling out a handful, I began to tease the moss to pieces, discovering almost instantly that it was infested with beetle larvae. The little grubs had taken on a glossy, plastic-like coating which froze them into the shape of a comma, and although they looked safe and secure in that improvised shell, I found that the very action of parting the moss had reduced three or four into total mush. I must have found two dozen of these pupae in the first handful of moss, and I uncovered a huge amount more from similar across the patch.

Just as a test, I dug in with my fingers at a range of spots around the area and found that the distribution of the grubs varied widely. In the grassy, drier areas there were almost none at all, whereas the deep, damp moss held dozens. They had not dispersed from the heather plants to any great extent, and the majority seemed to have fallen vertically off the leaves into the moss. Where the roots of the heather plants were damp enough, many larvae had gathered where there was no moss, making it seem as though moisture was the attraction, rather than moss. Even two or three inches away from heather plants there was a noticeable decrease in larvae numbers, and the impression I got was that they simply fell off the heather and, provided it was damp enough, they stayed put.

I will keep an eye on these brutes as they mature and emerge as adults in the autumn, but it occured to me that if those adults plan to eat any heather when they emerge, they’re going to be in for a nasty surprise. In their gluttony, the larvae have feasted on the heather to such an extent that the majority of plants have died. Many are now changing from fox-red to silver grey, indicating that they are giving up the ghost. At close quarters, several heather plants seem to have lost all their leaves, although I am convinced that the larvae don’t eat the leaves themselves. From what I saw, they preferred to fray and bother the leaves, chewing up the outer coating and maybe extracting something from the sap. In due course, the leaves become dry and brittle, finally falling off the plant rather than being munched.

This unexpected chance to study an outbreak of heather beetle is turning into a fascinating project. I just wish it wasn’t on the Chayne.

Turning from red to grey - these plants are knackered.
Turning from red to grey – these plants are knackered.

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