Giant Willow Aphid
Giant willow aphid (Tuberolachnus salignus) was first detected in Longford, Tasmania on 11 March 2014. This was the first record for Australia, and it was found soon afterwards across much of Northern Tasmania and a few locations in the greater Hobart area (Fig. 1). By April it had been found in parts of New South Wales and the ACT and subsequently found in Melbourne and Albury. Giant willow aphid (GWA) is found primarily on willows, but also sometimes on poplars, where it sucks sap from tree stems and young branches, often forming dense colonies. It remains unclear how and where the aphid first entered Australia.
Giant willow aphids produce copious amounts of honeydew from feeding, which can attract large numbers of bees and wasps, which feed on this sugary liquid. In particular, large numbers of European wasps have been observed on willows, creating a nuisance in localized areas where willows are prevalent.
Bees and Honey
A new concern has arisen with the spread of this pest. Reports from New Zealand (where GWA was first found in Dec 2013) have linked GWA to a phenomenon dubbed 'concrete honey'.
New Zealand beekeepers have found that when bees feed on large amounts of GWA honeydew, the honey they make can be hard and crystallized and difficult to extract. Honey yields are reduced and the attraction of large numbers of European wasps to the aphid honeydew can increase wasp attacks on beehives. Beekeepers are urged to monitor willows for this aphid in the vicinity of their hives to reduce the likelihood of 'concrete honey' and reduced yields.
DPIPWE Entomologists are keen to hear from any beekeepers that have experienced reduced honey quality as a result of this honeydew feeding. DPIPWE Entomologists would also like to encourage members of the public to report new sightings of giant willow aphid if they are outside of the currently mapped distribution (see Fig. 1). At present we have few reports for the south and east of Tasmania. Contact Lionel Hill on 0418 379 726.
Giant willow aphid is easy to spot and difficult to confuse with any other aphid. It is one of the largest aphids in the world (up to 6mm in length), dark grey in colour, with distinctive black spots and large tubercles (Fig. 2). Giant willow aphids build up dense colonies in summer, which persist through autumn, with populations reducing over the colder months (Fig. 3).
Map – Known distribution in Tasmania
Figure 1. Map of initial survey locations for giant willow aphid in Mar-Apr 2014. Green dots show where giant willow aphid was found. Red dots indicate areas of willow that were surveyed but no aphids found.
Figure 2. Giant willow aphid (image courtesy of Guy Westmore Department of Primary Industries, Parks, Water & Environment, Tasmania)
Figure 3. Dense colony of giant willow aphids (image courtesy of Alan Flynn, Ministry for Primary Industries, New Zealand)