Heather Beetle Control

Recent mild, wet winters and wet summers have produced severe heather beetle problems and the damage that this causes to heather is a periodic worry to landowners and conservation organisations. This dark brown beetle hibernates throughout the winter below the surface on the moors and emerges in spring as the temperature rises. It feeds lightly on heather, mates, lays eggs on damp areas of ground, particularly sphagnum moss and then dies.

By late May the eggs hatch into grubs, which are greenish yellow with black spots and 12 mm long. They invade the heather plants, eating young shoots and damaging stems, with the result that the heather turns a foxy-red colour by July before dying and going completely grey by the following spring. Seedlings and old heather are especially vulnerable to attack, leaving only young, vigorously growing heather capable of surviving. Because of this, the most carefully managed moors with appropriate grazing and burning patterns will suffer the least damage. By early August the grubs start to drop off the heather and bury into the litter to pupate into the adult beetle.

There are three options at present known to combat this pest. Some moorland managers advocate burning affected heather areas from mid-late July when all the eggs have hatched and the grubs are feeding on the heather and therefore exposed. Ground-nesting birds will have hatched and reared their chicks by this time, and it is prior to the start of the grouse shooting season. However, a licence must be obtained from DEFRA to burn out of season; the affected area must be identified, and this may not be easy, and finally there is an attendant risk of an uncontrolled fire causing far more damage than the beetle. The second option is to mow the affected heather to expose the larvae to bright sunlight, and the third, allied to reliance on biological control (see below) and favoured by many moor managers, is to burn the grey coloured dead heather early in the following year to give the best conditions for seed germination and growth of new plants.

Notwithstanding the damage that can be done by heather beetle, nature does have its own mechanism for keeping it in check. There is a small wasp that lays up to 15 eggs in young heather beetle grubs; these then hatch into parasitic larvae and infest the grubs. They have the effect of making the grubs leave the heather prematurely, therefore doing less damage and they also prevent the grubs from burrowing into the litter to pupate. Adult wasps emerge from the grubs in the following spring and attack the next generation of heather beetle grubs as they climb out of the litter. It is perhaps for this reason that heather beetle attacks are cyclical in nature.

Footnote 1 Less Favoured Areas are designated areas, mostly uplands, which are difficult, if not in some cases impossible to farm. Available land use statistics relating to heather moorland are all based on LFA information.