A new pest of cocoa in the British Solomon Islands,Megaceresium horniHeller (Cerambycidae), is described. The larvae cause severe damage to branches by tunnelling through the pith and sapwood, one larva may kill up to 3 m of branch in 4–6 weeks. In the outbreak reported, up to 5 branches per tree were infested on 58% of the trees. An intensive campaign of pruning and burning infested branches at 3–4 day intervals for one month, followed by pruning at two weekly intervals for three months, reduced the level of infestation from over 100 larvae per 100 trees to 2 per 100.