No. 246, March 2014 ISSN 1175-9755
TUBEROLACHNUS SALIGNUS, A NEW APHID ON THE BLOCK The giant willow aphid, Tuberolachnus salignus The degree of injury to the host plants is not well (Hemiptera: Aphididae) was first found in New Zealand documented, however an overseas study on potted and on 23 Dec 2013 at Western Springs Park, Auckland by hydroponic cuttings of willow reported that giant willow entomologist Stephen Thorpe. Surprisingly, subsequent aphid caused drastic growth reductions during and surveys have revealed that it is already well established subsequent to infestation, and also altered the mass of throughout much of New Zealand (see map). previously developed woody tissue. In New Zealand the extent of the damage remains to be seen, but this pest Tuberolachnus salignus is virtually cosmopolitan and could pose problems where willows are used for flood is highly conspicuous. It is one of the largest known protection and in shelterbelts. aphids (up to 6 mm in body length) and is patterned with spots and sports a “shark’s fin” tubercle on the dorsum Thus far in New Zealand the aphid has been reported from (see photo). It feeds on sap from the young stems and Salix alba var. vitellina, S. babylonica, S. caprea, S. cinerea, branches of its host trees, which include species of Salix S. fragilis, S. humboldtiana, S. matsudana, S. viminalis, S. x (willow) and occasionally, Populus (poplar). sepulcralis and Populus nigra. Large dense colonies of the giant willow aphid form over No parasitoids have been observed in New Zealand, summer. Reproduction occurs asexually with no males however possible predators include ladybirds which have having ever been found, thus the aphids in these colonies been found in association with colonies of T. salignus: are typically clones. The aphids are noted to be long Adalia bipunctata and possibly Halmus chalybeus though lived, with winged individuals in particular displaying the latter is known primarily as a scale predator and lengthy maternal care of their offspring. In Great Britain may have been more attracted to honeydew residues colonies are apparent from mid-summer into late winter, produced by the aphid. Interestingly, entire colonies of the after which the aphids curiously disappear in spring. We aphids elsewhere have been observed waving their hind may expect to see a similar trend in New Zealand with legs in the air in response to the presence of predators. T. salignus present between December and July. Other insects associated with T. salignus include various honeydew feeders. There are reports of significant Vespula spp. wasp activity around honeydew deposits at
Tuberolachnus salignus aphid. Tuberolachnus salignus colony.
Newsletter of the Scion Forest Protection team, and the Forest Health Reference Laboratory (incorporating the Forest Research Mycological Herbarium (NZFRI-M), the Forest Research Culture Collection (NZFS), and the National Forest Insect Collection (FRNZ). Edited by John Bain, New Zealand Forest Research Institute Ltd, Private Bag 3020, Rotorua.
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