Eriococcus orariensis
From Wikipedia, the free encyclopedia
| Eriococcus orariensis | |
|---|---|
 | |
| Eriococcus orariensis nymph | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Hemiptera |
| Suborder: | Sternorrhyncha |
| Family: | Eriococcidae |
| Genus: | Eriococcus |
| Species: | E. orariensis |
| Binomial name | |
| Eriococcus orariensis Hoy, 1954 | |
Eriococcus orariensis, commonly known as the mānuka blight, is a felt scale insect in the genus Eriococcus. It is native to Australia, but was discovered in New Zealand in 1937 after being accidentally introduced to the country.
To identify and differentiate Eriococcus orariensis from similar Eriococcus species a microscope is needed.[1] E. orariensis is sexually dimorphic. Adult females are typically light brown and an oval shape that tapers towards the anal lobes.[2] Adult females lack wings and average 1.25mm in length and 0.84mm in width.[3] Their antennae are six-segmented, the third segment being the longest. Female egg sacs are also greyish-white, closely felted, and open towards the anal end.[3]
Eriococcus orariensis female dorsal (upper) and ventral (lower) body surfaces are membranous and irregularly covered in small, inconspicuous, bristle-like structures called setae; although the setae extend in semi-regular rows along the abdominal segments.[3] There is no noticeable marginal fringe of setae on the dorsum, again excepting the distinct abdominal segments.[3] A small number of quinquelocular sessile pores exist on the ventral abdominal segments in association with respiratory openings called spiracles.[3] Contrastingly, long tubular ducts ending in cup-shaped pores cover the dorsum in moderate numbers, also concentrating on abdominal segments.[3]
Eriococcus orariensis female anal lobes are cylindrical for two-thirds their length before tapering towards the base of much longer caudal (tail-like) setae.[2] A prominent feature used to differentiate E. orariensis from other Eriococcus species in a key created by the entomologist, Dr James Mather Hoy,[3] are three dorsal setae on the anal lobe: two towards the base and one two-thirds the distance up towards the inner margin. The anal ring has eight setae.[2] Legs in both mature sexes are well developed,[2] but relatively small for the species' size.[3] Back leg tarsi are longer than tibiae.[3] Curved claws at the end of each leg have a small tooth-like projection.[3]
Eriococcus orariensis adult males are smaller than females, averaging 0.84mm in length.[2] They are typically reddish-yellow with an abdominal spike and a pair of long filaments extending from the second to last abdominal segment.[2] They have iridescent wings fringed with hairs, and halteres with a hook-like projection called a hamulus.[2] Male puparia are oval, white, cottony and not as closely felted as females.[3] Male antennae are ten-segmented with many setae, but the third segment is also longest.[2] They have four light-detecting organs called ocelli: two close together on the mid-ventral surface, and two on the lateral margins.[3] Adult males also have no mouthparts.[3] Their legs are very setose, with a longer spine-like seta on each tibia.[3]
The first instar nymphs of Eriococcus orariensis are pale pink or brown, with an average a 0.37mm length and 0.17mm width.[2] They are most similar to adult females, with slight differences. For example, nymph anal lobes are more cone-like, their dorsal abdominal setae are more spine-like and arranged in rows lengthwise, and they only have six setae on their anal ring.[2]
Range
Eriococcus orariensis is native to Australia.[4] There they are widely distributed through Southern and Eastern Australia, including Tasmania,[4] but populations exist in low numbers there due to an abundance of natural predators and parasitoid species.[5]
Eriococcus orariensis was first discovered in New Zealand in 1937 at Orari Gorge, Canterbury.[4] It was introduced from Australia, but exactly when and how is unknown.[2] The most likely theory is that it was accidentally introduced on imported ornamental Leptospermum scoparium (mānuka) plant material.[2]
Initially, Eriococcus orariensis appeared restricted to Orari Gorge, with a slow spread through surrounding Geraldine through the 1940s.[1] However, in the late 1940s-50s E. orariensis was deliberately spread to farms across the country due to its ability to kill mānuka within years of attack, which was considered a major pasture weed at the time.[1] By 1954 it was widespread through mānuka populations on both main islands, likely aided by its release from natural enemies only found in Australia.[2]
Today, although exact distributions of Eriococcus orariensis in New Zealand are unknown, it appears their population has been dramatically reduced in range to several sites in Nelson, Otago, Fiordland, and the West Coast, and replaced by the scale insects Acanthococcus campbelli (Hoy) and Acanthococcus leptospermi (Maskell).[1][5] This is likely due to parasitism by the entomogenous fungi, Angatia thwaitesii Petch, 1924, discovered in New Zealand in 1957.[5]
Habitat
Eriococcus orariensis is host-specific to six species of Leptospermum plants in Australia.[4] In New Zealand it is only found on Leptospermum scoparium (mānuka) and Kunzea ericoides (kānuka - previously Leptospermum ericoides).[4] It can survive in all places those trees grow, but consistently establishes at higher rates on mānuka, as mānuka bark does not exfoliate in papery sheets like kānuka does, so offers many more establishing sites for the insect.[4] E. orariensis occupies the specific niche of mānuka bark crevices in trunks and branches to avoid competition with other scale insects like Eriococcus leptospermi which occupies new plant growth.[1] While male puparia sacs tend to cover the surface of sooty mold and bark on mānuka plants, female egg sacs and early E. orariensis stages tend to stay sheltered under the bark.[2]