New hairy caterpillar alert in Auckland suburb of Mt Wellington

The Ministry of Agriculture and Forestry (MAF) is encouraging Aucklanders to remain on the lookout for unusual caterpillars after a member of the public spotted what could be a new exotic species at an Aranui Street property in Mt Wellington last Wednesday.

“The incidence of tree pests in the Auckland region seems to be on the rise and that is of concern to MAF,” said Peter Thomson, MAF’s Director of Forest Biosecurity.

The hairy caterpillars found in Mt Wellington have provisionally been identified as the fall webworm (Hyphantria cunea). Newly hatched larvae spin a silken web over the foliage on which they feed and this can result in the presence of large, unsightly webs. An inspection of neighbouring properties has turned up one communal web with live caterpillars on a single tree.

The fall webworm belongs to the tiger moth family of which there are approximately 11,000 species worldwide. It is native to North America and Mexico and is known as an insect that will feed on a range of species of plants. Shade trees and ornamentals can be heavily defoliated. In the US, Canada and Japan the fall webworm is reported showing a preference for cherries, mulberry, dogwoods, sycamores, persimmons, poplar, aspen, willows, white birch, apple tree and sweetgum. It is not regarded as a serious pest in the US. It became well established in Europe from the 1950s but is no longer spreading and is only locally damaging.

“We have immediately moved on to initiate surveys, trapping and testing the range of plant species likely to host the fall webworm,” said Mr Thomson.

“This is another classic case of the importance of having public participation in biosecurity through reporting of a suspected pest to the MAF hotline 0800 809 966. Biosecurity agencies can’t by themselves deliver a 100% guarantee of keeping all exotic species out of our land, air and sea space, so we place a high premium on the importance of public awareness. MAF Quarantine Service staff perform numerous interceptions every day and do an excellent job – it’s the job of our dedicated response teams in Forest and Plants Biosecurity to swing into action to respond to post-border detections rapidly and effectively”.

Events to date: Late Wednesday – MAF responded to a public enquiry made to MAF about a suspicious hairy caterpillar. Thursday – Contact made with enquirer and site visit organised. Friday – Caterpillar specimens sent to MAF laboratory for preliminary identification and MAF staff undertake wider inspection. Specimen images sent to US Department of Agriculture for validation. Saturday – MAF contractor applied pesticide to host tree and hosts on surrounding properties. Sunday/ Monday – Initial investigation report completed by MAF staff including recommendations for initial response.