Live plants are often traded in winter or early spring when the number of pests
is potentially low, in part because deciduous trees lack foliage. However, the
pests that may be associated with traded dormant plant material are likely to be
largely unknown. Pest risk assessments can only be performed for known pest
species and it is therefore important to identify potential pests before they are
moved to a new area. In addition, it is difficult to predict whether introduced
pests, even if already well known, may shift host after their arrival. Several
studies attempted to estimate the likelihood of host shifts using literature about
known pest-host associations, but the number of pests in these studies was
often limited and the data were unlikely collected in the same place and at the
same time. To overcome these problems, we performed a global study which
aimed at detecting potential insect pests and fungal pathogens on congeneric
native and exotic woody plant species that belong to six studied tree genera.
Sampling was done simultaneously in 33 countries around the world following a
common sampling protocol. At each location, twenty 50 cm long, dormant twigs
were collected from each tree species and kept in containers with water at room
temperature. Emerged insects were collected and identified based on
morphology and DNA barcoding of the mDNA COI region. Fungal DNA was
extracted from pooled buds, twig parts and needles for species identification
using a metabarcoding approach based on the rDNA ITS region. Here, we
present preliminary results of this study and discuss them in the context of pest
risk assessment.