Changes to the composition of scale insect species (Coccomorpha: Eriococcidae) on New Zealand manuka (Leptospermum scoparium; Myrtaceae) in the last seventy years

Abstract

The perception of Leptospermum scoparium (mānuka) in New Zealand has changed from a weed to a valued shrub over the last half century due to the economic benefits of mānuka honey. The scale insect Acanthococcus orariensis (Hoy) (Hemiptera: Eriococcidae), an accidental control agent of L. scoparium that caused the mānuka blight mass dieback in the 1940s, initially was common, but declined once the entomogenous fungus Angatia thwaitesii (Petch) Arx (Fungi: Myriangiaceae) appeared. Subsequently, Acanthococcus campbelli (Hoy) and Acanthococcus leptospermi (Maskell) appear to have replaced Ac. orariensis in the last few decades, but there is limited knowledge on their current distribution. The distribution of Acanthococcus species on L. scoparium was determined at 28 sites throughout New Zealand. The most widespread species was Ac. leptospermi, which was found at 23 sites, whereas Ac. campbelli was found at 13 sites, and Ac. orariensis at just two sites. It appears that Ac. leptospermi is now the most common Acanthococcus species on New Zealand Leptospermum, and the blight caused by Ac. orariensis has not returned.