Protecting Canada's cherry trees from pests

Overview

Results

The team

Related information

So what's the problem?

Since the first discovery of cherry bark tortrix, Enarmonia formosana (Scopoli) (Lepidoptera: Tortricidae), in British Columbia, Canada in 1989, populations of this pest species have increased and expanded southward into Washington and Oregon States, USA. Enarmonia formosana larvae feed beneath the bark of Prunus and other related rosaceous trees, inflicting significant damage to the phloem and cambium layers and in some cases causing eventual death of the tree.

During its introduction from its native range of Eurasia and northern Africa, E. formosana appears to have been separated from the natural enemies normally keeping its population under control. Recognising the threat that E. formosana poses to the lucrative nursery and orchard industries on North America’s west coast, a project was initiated in 1998 to try to identify a biological control solution for this pest.

What is this project doing?

The main objectives of the project were:

Obtaining Campoplex species belonging to the Campoplex difformis group to verify identifications and to clarify Campoplex dubitator-host associations
Defining the host range of Campoplex dubitator
Investigating chemical cues involved in the host location and host recognition of Campoplex dubitator
Sequencing of Campoplex dubitator

Surveys conducted in central Europe between 1998 and 2002 identified several parasitoid species attacking European E. formosana populations. Of these, the larval-pre-pupal parasitoid, Campoplex dubitator Horstmann (Hymenoptera: Ichneumonidae) was found to be the most dominant and has been the subject of research over the last few years. Due to taxonomic uncertainties, molecular studies have been carried out to try to clarify the species status of this parasitoid. This information is vital for a parasitoid release petition.

Behavioural and physiological studies were conducted to compare C. dubitator and C. capitator, a parasitoid that attacks the grape berry moth, Lobesia botrana, and which remains molecularly indistinct from C. dubitator. Additional experiments have been conducted to investigate chemical cues used by C. dubitator during host location and thereby identify microhabitats in which the parasitoid forages. This has been used as a method of prioritising non-target species for host range testing since species that occur in areas where the parasitoid forages are most likely to be at risk from parasitism.

Results so far

Results from bioassays using a four-arm olfactometer indicate that parasitoid females strongly prefer the odour of cherry bark to that of cherry leaves. This suggests that species living in and around the tree bark are more likely to be encountered by C. dubitator than leaf-dwellers and should thus be given priority in host range tests. Behavioural tests further indicate that C. dubitator and C. capitator, which are molecularly indistinct, are in fact two distinct parasitoid species.

Project Manager