The effect of heather beetle Lochmaea suturalis on vegetation in a wet heath in NE Scotland

Abstract

An outbreak of heather beetle Lochmaea suturalis on a wet heath in north‐east Scotland was monitored. In many respects, the outbreak was similar to those described in lowland heaths; it started at a particular locus and when the Calluna vulgaris was depleted, spread throughout the heath. Population size then decreased annually due to some undetermined exogenous factor. A contributory factor may be the high incidence (35%) of parasitoid infestation which is density independent and, thus, not controlling.There is no evidence that the hairiness of the var. hirsuta of Calluna has an effect on herbivory by Lochmaea. The distribution of larvae through the canopy is neither influenced by the morphology of Calluna, nor by the associated species, and appears to be at random. This probably represents the distribution of eggs since little lateral migration of the larvae takes place.The response of the vegetation to herbivory is not simple. Associated with decreased cover of Calluna is an increase in Sphagnum plumulosum and Hypnum jutlandicum and reduction in S. compactum and Pleurozium schreberi. Changes seem to depend on initial vegetation and other parameters not measured (e.g. proximity of propagules, microclimate). Regeneration of Calluna does occur, largely by layering; although seedling occurrence increases in some areas, especially in Sphagnum, it seems unlikely that this will make a major contribution to the recovery of Calluna.