Effect of Sirex noctilio (Hymenoptera: Siricidae) attack density on Pinus sylvestris (Pinaceae) survival
Laurel J. Haavik, Brett P. Hurley, and Jeremy D. Allison
Population density is often a critical
factor in colonisation of trees by bark and wood-boring insects and may
determine whether an exotic species is likely to establish and spread.
In a manipulative field study, we investigated whether density of the
attacking population of an exotic invasive woodwasp, Sirex
noctilio Fabricius (Hymenoptera: Siricidae), affected survival and
time-to-death of a favoured host tree, Pinus sylvestris Linnaeus
(Pinaceae). We introduced mating pairs of woodwasps to stressed P.
sylvestris at either high (15 mating pairs, nine trees) or low (two
mating pairs, nine trees) density. More trees died, and more quickly,
when exposed to the high versus low density of S. noctilio (78% versus
33% of trees). In the high-density treatment, year of tree death was
synonymous with production of a S. noctilio F1 cohort (one-year or
two-year generation time); this pattern was not as consistent in the
low-density treatment. Although sample size was limited, our results
indicate that attack density affects S. noctiliocolonisation of P.
Source: Cambridge University Press