INTERESTING INSECTS

By N A Martin (2010, revised 2019)

Pittosporum psyllid, Pittosporum chermid

Powellia vitreoradiata Maskell, 1879

Trioza alexina Marriner, 1903

Trioza pellucid Maskell, 1890

This endemic psyllid lives in the North and South Islands of New Zealand. It lives on its host plants, Pittosporum species, in city gardens and parks as well as native ecosystems. It has been accidentally transferred to the British Isles where it is present in Cornwall and the Scilly Isles and infests New Zealand and East Asian Pittosporum species.

Conservation status: Widespread, not threatened, a minor pest in gardens and foliage crops.

This insect overwinters as adults, probably females that were mated the previous autumn. Adult males and females are about 2 mm long, have transparent wings held over their abdomens and three pairs of legs each. The body has distinctive markings that tend to be darker in the male. The male has a complex apparatus at the tip of the abdomen that is used for grasping the female during mating. While mating the male sits alongside the female, facing in the same direction, and the end of the abdomen curls under the female and the tip of her abdomen. The tip of the female’s abdomen is slender and houses a narrow blade-like ovipositor that assists with egg laying.

Eggs

Overwintering females lay eggs on new growth in the spring. They insert eggs between the hairs on the underside of leaves, between hairs at the base of young leaf stalks and probably between the unfurling young leaves. Eggs are shining, smooth, irregularly tear-shaped, and they taper to a point with a short spine. The egg base has a short stalk that may be inserted into the plant. The newly laid eggs are pale cream, darkening to pale orange, with the basal third darker than the rest. A few days before hatching red eyespots are present. Eggs are about 0-35 mm long. A female may lay from 67 to 415 eggs (190 eggs on average). Eggs may take 14 days to hatch.

Scale-like nymphs

Nymphs hatch from the eggs. First instar (stage) nymphs are small, orange-brown and oval shaped. They have three pairs of legs and sucking mouthparts. They settle on a young leaf, mainly on the underside. There are five nymphal stages, and each is called an instar. Nymphs go from one stage to the next by moulting (changing their skin). During moulting, the skin on the dorsal side splits and the next stage pulls itself out of the old skin. Adults emerge from fifth instar nymphs.

As the insects progress through the nymphal stages their colour and shape changes. They become flat like a scale insect and develop wing buds. Also the lateral fringe of filaments becomes longer and denser and the antennae develop more segments. The second instar nymphs are orange and have two-segmented antennae like the first instars. However, they also have small wing buds. Third instar nymphs may be darker in colour and have three-segmented antennae. The fourth and fifth instar nymphs vary in colour from almost white to a dark brown and have four- and six-segmented antennae, respectively. The fully grown fifth instar nymph is about 1.9 mm long. The young nymphs have setae (hairs) on their upper surfaces, but the last three instars may be either hairless or very hairy. This does not appear to be linked to the hairiness of the leaf on which they are living or whether they are on the upper (hairless) or under (hairy) sides of the leaves.

The length of time needed for nymphal development depends on the temperature. In a 1940s study, probably in a screen house in Auckland, development of all five stages took about 45 days.

There is a spring generation on the flush of young leaves. The psyllid may be able to complete more than one generation in the spring by moving between host plants that come into leaf at different times. Later in the summer and autumn, adult female psyllids may lay eggs on host plants that produce young leaves. Often there is an autumnal flush of leaves on which the psyllid breeds.

Walking, jumping and flying

Adults and all nymphal stages possess three pairs of legs that are used for walking. When the adults are at rest and walking the last pair of legs are held under the body (see photo of underside of adult male). These hind legs are used make the adult jump if it is disturbed. And hence a common name for psyllids, jumping plant lice. The adults also possess wings and can fly, which aids dispersal and location of new host plants.

Feeding and honeydew

Like other Hemiptera, the pittosporum psyllid has sucking mouthparts. The long stylets, which are specially shaped rods, are held in the rostrum. When it wishes to feed the psyllid moves the tip of the rostrum to the surface of a leaf or stem. The stylets are then gradually pushed into the plant. The stylets form two tubes, one through which saliva is injected into the plant and a second through which plant juices are sucked up into the insect. The pittosporum psyllid inserts the stylets into the phloem (the plant vessels for transmitting sap from the leaves to other parts of the plant). The sap has a high volume of water and sugars, more than the insect needs. The psyllid excretes the excess water and sugar, which is called honeydew. The pittosporum psyllid coats the droplet of honeydew with white wax before ejecting it. Leaves can become covered with these white wax-coated droplets which are called psyllid sugars.

Newly emerged adult female pittosporum psyllid Trioza vitreoradiata (Hemiptera: Triozidae), on the underside of a Pittosporum crassifolium leaf; the newly emerged adult is pale and darkens over the following few days. Creator: Tim Holmes. © Plant & Food Research. [Image: 3HF]

Adult female pittosporum psyllid Trioza vitreoradiata (Hemiptera: Triozidae). Creator: Myra Carter. © drawing published in New Zealand Journal of Science and Technology, 1949 Section B 31: 1-42, Figure 2. [Image: 3IF]

Side view of an adult male pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae), note the large external genitalia. Creator: Tim Holmes. © Plant & Food Research. [Image: 3HP]

Underside of an adult male pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae), note the large external genitalia. Creator: Tim Holmes. © Plant & Food Research. [Image: 3HO]

Newly laid eggs pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae), inserted into the hairy leaf bases of Pittosporum crassifolium. Creator: Tim Holmes. © Plant & Food Research. [Image: 3HQ]

Orange eggs of pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae), inserted into the young hairy leaves of Pittosporum crassifolium. Creator: Tim Holmes. © Plant & Food Research. [Image: 15VK]

Juvenile pittosporum psyllids, Trioza vitreoradiata (Hemiptera: Triozidae). Creator: Myra Carter. © drawing published in New Zealand Journal of Science and Technology, 1949 Section B 31: 1-42, Figure 1. [Image: 3IE]

First instar (stage) pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae), nymph on a Pittosporum crassifolium leaf. Creator: Tim Holmes. © Plant & Food Research. [Image: 3HR]

Large and small pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae), nymph on a Pittosporum crassifolium leaf; the dorsal, or top, side of the nymph is hairless. Creator: Tim Holmes. © Plant & Food Research. [Image: 3HL]

Large pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae), nymph on a Pittosporum crassifolium leaf; the nymph is dark and the dorsal, or top, side has many short hairs. Creator: Tim Holmes. © Plant & Food Research. [Image: 3HG]

Large pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae), nymph on a Pittosporum crassifolium leaf; the nymph is pale and the dorsal, or top, side is hairless. Creator: Tim Holmes. © Plant & Food Research. [Image: 3HI]

Large pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae), nymph on a Pittosporum crassifolium leaf; the nymph is pale and the dorsal, or top, side has a few hairs. Creator: Tim Holmes. © Plant & Food Research. [Image: 3HH]

Large pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae), nymph on a Pittosporum crassifolium leaf; the nymph is pale and the dorsal, top side, has many short hairs. Creator: Tim Holmes. © Plant & Food Research. [Image: 3HK]

Hairy nymphs of pittospoprum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae), on the upper side of leaves of Pittosporum crassifolium. Creator: Tim Holmes. © Plant & Food Research. [Image: 3HN]

Hairy nymphs of pittospoprum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae), on the underside of leaves of Pittosporum crassifolium. Creator: Tim Holmes. © Plant & Food Research. [Image: 3HM]

High numbers of Pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae) on a young shoot of Karo, Pittosporum crassifolium with psyllid ‘sugars’ on a leaf. The white ‘sugars’ are wax-coated honeydew droplets ejected by the psyllid. Creator: Nicholas A. Martin. © Nicholas A. Martin. [Image: 2L80]

An adult Pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae) emerging from its nymphal skin: note the white wings that will expand once the adult is free. Creator: Nicholas A. Martin. © Nicholas A. Martin. [Image: 2L7Y]

An adult Pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae) emerging from its nymphal skin: note the white wings that will expand once the adult is free. Creator: Nicholas A. Martin. © Nicholas A. Martin. [Image: 2L7Z]

There are several kinds of psyllids in New Zealand, the adults of which look very similar to the pittosporum psyllid and can only be distinguished through microscopic examination. However, only this species, Trioza vitreoradiata, breeds on Pittosporum trees.

Two other groups of insects that live on Pittosporum species could be confused with adult or juvenile psyllids. Winged aphids are similar in size to adult psyllids, but have globular bodies and hold their wings above their bodies whereas psyllids are more like tiny cicadas, slender with the wings covering the body when they are at rest. Furthermore, the abdomen of the adult psyllid often twitches from side to side.

Whitefly larvae are similar to the flat psyllid nymphs. However, they cannot walk and do not have wing buds. They also tend to occur in clusters on the underside of older leaves.

Side view of an adult male pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae), note the large external genitalia. Creator: Tim Holmes. © Plant & Food Research. [Image: 3HP]

An aphid holding its wings above its body; melon aphid (Aphis gossypii Glover, 1877 (Hemiptera: Aphididae). Creator: DSIR photographers. © Plant & Food Research. [Image: 3HB]

Large and small pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae), nymph on a Pittosporum crassifolium leaf; the dorsal, or top, side of the nymph is hairless. Creator: Tim Holmes. © Plant & Food Research. [Image: 3HL]

Large pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae), nymph on a Pittosporum crassifolium leaf; the nymph is dark and the dorsal, or top, side has many short hairs. Creator: Tim Holmes. © Plant & Food Research. [Image: 3HG]

Puparia of whitefly on underside of leaf of Pittosporum eugenioides (lemonwood). Creator: Tim Holmes. © Plant & Food Research. [Image: 15VN]

Tiny first instar (stage) nymphs of pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae), on an expanding bud of Pittosporum crassifolium. Creator: Tim Holmes. © Plant & Food Research. [Image: 1V52]

No pathogens of the pittosporum psyllid are known.

Predators

Birds also probably feed on the psyllid, but there are no specific reports. Spiders and several species of lacewings, ladybirds and mirid bugs feed on adult and juvenile pittosporum psyllids.

Both adults and larvae of the lacewing, Drepanacra binocula (Newman, 1838) (Neuroptera: Hemerobiidae), feed on the psyllid larvae, and the adult lacewing also feeds on the adult psyllids. The Tasmanian lacewing, Micromus tasmaniae (Walker, 1860), and Wesmaelius subnebulosus (Stephens, 1836), both in the family Hemerobiidae, also feed on the pittosporum psyllid. The latter was the least common in a 1940s study where it was called Boriomyia maorica Tillyard.

Several species of ladybird (Coleoptera: Coccinellidae) feed on pittosporum psyllid adults and nymphs. The steely blue ladybird, Halmus chalybeus (Boisduval, 1835) (Coleoptera: Coccinellidae), is the commonest species seen on pittosporum psyllid host plants in Auckland. Other species feeding on the psyllid include two-spotted ladybird, Adalia bipunctata (Linnaeus, 1758), the large spotted ladybird, Harmonia conformis (Boisduval, 1835) and native species, Adoxellus flavihirtus (Broun, 1880).

Adults of two other species of ladybird have been found associated with infestations of the psyllid on young plant leaves, Coelophora inaequalis (Fabricius, 1775) and Cryptolaemus montrouzieri Mulsant, 1853. These two ladybirds have not been observed feeding on psyllids, but may instead be feeding on the honeydew they produce.

Two species of predatory sucking bugs (Hemiptera: Miridae) have been found in association with the pittosporum psyllid. One species, Ausejanus albisignatus (Knight, 1938) which is known to prey on this psyllid in the laboratory is the most common mirid where pittosporum psyllids are present. The red-cross mirid, (Zanchius rubicrux Eyles, 2005) was seen less often in recent studies of the natural enemies of the pittosporum psyllid.

Parasitoids

Two species of parasitoid wasps (Hymenoptera) have been reared from pittosporum psyllid nymphs. An undescribed species in the family Encyrtidae was found in a 1940s study by M. Carter. The wasp larvae lived in the nymph and pupated in the nymphal skin. The second parasitoid, Tamarixia sp. (Eulophidae), was first found in 1997 and is now very common in Auckland. High levels of parasitism of the pittosporum psyllid occur in autumn. This parasitoid lays its eggs near the bases of psyllid nymph legs, and the parasitoid larva feeds externally on the underside of the nymph. The adult parasitoid chews an exit hole in the skin of the dead nymph.

Adult lacewing, Drepanacra binocula (Newman, 1838) (Neuroptera: Hemerobiidae), which feeds on pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae). Creator: Martin Heffer. © Plant & Food Research. [Image: 3I1]

Lacewing larva, Drepanacra binocula (Newman, 1838) (Neuroptera: Hemerobiidae) feeding on pittosporum psyllids, Trioza vitreoradiata (Hemiptera: Triozidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 3I2]

Adult Tasmanian lacewing, Micromus tasmaniae (Neuroptera: Hemerobiidae). © Plant & Food Research. [Image: 3FL]

Larva of Tasmanian lacewing, Micromus tasmaniae (Neuroptera: Hemerobiidae). © Plant & Food Research. [Image: 3FO]

Adult steely blue ladybird, Halmus chalybeus (Boisduval, 1835) (Coleoptera: Coccinellidae), a predator of pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 3HT]

Larva of steely blue ladybird, Halmus chalybeus (Boisduval, 1835) (Coleoptera: Coccinellidae), a predator of pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 3I3]

Adult two-spotted ladybird, Adalia bipunctata (Linnaeus, 1758), (Coleoptera: Coccinellidae), a predator of pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 3IH]

Larva of two-spotted ladybird, Adalia bipunctata (Coleoptera: Coccinellidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 15VG]

Adult large spotted ladybird, Harmonia conformis (Boisduval, 1835), (Coleoptera: Coccinellidae), a predator of pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 3I4]

Larva of a large spotted ladybird, Harmonia conformis (Boisduval, 1835), (Coleoptera: Coccinellidae), a predator of pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 3I5]

Adult yellow haired ladybird, Adoxellus flavihirtus (Coleoptera: Coccinellidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2860]

Larva of yellow haired ladybird, Adoxellus flavihirtus (Coleoptera: Coccinellidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2861]

Adult Xiphoides sp. (Hemiptera: Miridae), a predator of the pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 285T]

Adult Xiphoides sp. (Hemiptera: Miridae), a predator of the pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 285U]

Adult Ausejanus albisignatus (Knight, 1938), (Hemiptera: Miridae), a predator of the pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 3ID]

Adult male red-cross mirid, Zanchius rubicrux (Hemiptera: Miridae). Creator: Minna Personen. © Plant & Food Research. [Image: 15VH]

Adult female red-cross mirid, Zanchius rubicrux (Hemiptera: Miridae). Creator: Minna Personen. © Plant & Food Research. [Image: 15VI]

Drawing of adult parasitoid (Encyrtidae) reared from the pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae). Creator: Myra Carter. © drawing published in New Zealand Journal of Science and Technology, 1949 Section B 31: 1-42, Figure 2. [Image: 3IG]

Exit holes in nymphs of pittosporum psyllids, Trioza vitreoradiata (Hemiptera: Triozidae), made by an endoparasitic wasp (Hymenoptera). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 285V]

Adult female Tamarixia sp. (Eulophidae), an ectoparasitoid of juvenile psyllids. Creator: Tim Holmes. © Plant & Food Research. [Image: 2864]

Adult female Tamarixia sp. (Eulophidae), a parasitoid of juvenile psyllids. Creator: Tim Holmes. © Plant & Food Research. [Image: 3I9]

Adult male Tamarixia sp. (Eulophidae), a parasitoid of juvenile psyllids; note the branched antennae. Creator: Tim Holmes. © Plant & Food Research. [Image: 3I7]

Adult female Tamarixia sp. (Hymenoptera: Eulophidae) inspecting a pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae), nymph. Creator: Tim Holmes. © Plant & Food Research. [Image: 3I8]

An egg of Tamarixia sp. (Eulophidae) laid between the base of the first two legs of a pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae), nymph. Creator: Tim Holmes. © Plant & Food Research. [Image: 3IA]

Larva of Tamarixia sp. (Eulophidae) on the underside of a pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae), nymph. Creator: Tim Holmes. © Plant & Food Research. [Image: 3IB]

Exit hole for an adult Tamarixia sp. (Eulophidae) from a parasitized pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae), nymph. Creator: Tim Holmes. © Plant & Food Research. [Image: 3IC]

The common host plants are four endemic species of Pittosporum. A fifth species, Pittosporum fairchildii, which comes from the Three Kings Islands, is a host plant, but plants growing in Auckland City have only a few leaves exhibiting typical psyllid damage. There is a report that Pittosporum ellipticum is a host plant, but this has not been confirmed. There is also an unsubstantiated report that feijoa (Feijoa sellowiana O. Berg (Myrtaceae)) can be a host plant.

The Australian tree, Hymenosporum flavum (Hook.) F.Muell., which belongs to the Pittosporaceae, is a very rare, occasional host plant.

Feeding and plant damage

When the psyllid nymph settles and feeds on a young expanding leaf, a pit gall is formed. This happens when the nymph settles on the upper or lower side of the leaf. In a heavy infestation a leaf can become badly distorted. Psyllid nymph feeding also causes areas of the leaf to turn yellow. The presence of dimples and yellow areas on leaves makes it easy to recognise leaves that have been infested by this insect.

Adult and juvenile psyllids feed on phloem and secrete excess water and sugars (honeydew). The droplets of honeydew are coated with wax before ejection. These droplets are termed ‘psyllid sugars’. They can be seen where there are high infestations of nymphs, such as sometimes occurs on Pittosporum crassifolium. Where there is a lot of honeydew on plant leaves, black ‘sooty’ mould fungi grow, living on the sugars.

Why some plant species are heavily infested

Pittosporum crassifolium tends to have high infestations of pittosporum psyllids. This insect is much less common on some other species.

Two factors appear to be involved: suitable places to lay eggs and availability of young leaves. On its favoured host plant, Pittosporum crassifolium, the psyllid inserts its eggs amongst the dense hairs on the underside of leaves. On the much less hairy Pittosporum tenuifolium, eggs are inserted between the hairs at the base of young leaves still in a bud. Pittosporum fairchildii is not a favoured host. It has a few hairs at the base of young leaves, but produces young shoots in late winter, early spring, well before the local species in Auckland produce shoots. It may be too early for most adult psyllids.

Another host plant with low infestations is Pittosporum eugenioides. It has smooth leaves and no leaf hairs. Leaves in the shady part of the tree tend to be infested. It may be that eggs are inserted between the expanding leaves, but only less ‘tough’ leaves in the shade are suitable for psyllid nymphs to grow.

Pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae), damage on upper side of Pittosporum eugenioides (lemonwood) leaf; note the yellow areas and the dimples, or cavities in which nymphs are sitting. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 3HU]

Pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae), damage on underside of Pittosporum eugenioides (lemonwood) leaf; note the yellow areas and the raised underside of pit galls. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 3I0]

Pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae), damage to the underside of a Pittosporum colensoi leaf; note the raised underside of pit galls. The psyllid nymph sits in the pit on the other side of the leaf. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 3HC]

Pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae), damage to the upper side of Pittosporum tenuifolium leaves; note the raised underside of the pit galls on the upper side of the new leaves and the psyllid nymphs in the pits on the underside of the leaf (see insert of detached leaf). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 3HZ]

Pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae), damage to the upper side of Pittosporum crassifolium (karo) leaf; note the yellow pit galls. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 3HV]

An example of severe pittosporum psyllid damage to young leaves of Pittosporum crassifolium (karo); note the yellow areas and pit galls, pits on underside of leaf with corresponding raised areas on the other side of leaf. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 3HW]

Psyllid ‘sugars’ on leaves of Pittosporum crassifolium (karo). The white ‘sugars’ are wax-coated honeydew droplets ejected by the pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 3HE]

Pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae), damage to the upper side of Pittosporum huttonianum leaves; note the pit galls in which the psyllid nymph sits. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 18T1]

Pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae), damage to the underside of a Pittosporum huttonianum leaf; note the raised underside of pit galls. The psyllid nymph sits in the pit on the other side of the leaf. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 18T2]

High numbers of Pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae) on a young shoot of Karo, Pittosporum crassifolium with psyllid ‘sugars’ on a leaf. The white ‘sugars’ are wax-coated honeydew droplets ejected by the psyllid. Creator: Nicholas A. Martin. © Nicholas A. Martin. [Image: 2L80]

Adults of two species of ladybirds have been found associated dense colonies of the psyilld where there was fresh honeydew on leaves. Adults of the Mealybug ladybird, Cryptolaemus montrouzieri, have been found several times in this association.

Adult beetles (Melyridae) have been found associated with trees infested with psyllids. The adult beetles are known to feed in flowers and may be feeding on psyllid honeydew.

Flies are also associated with honeydew on leaves of trees near beaches.

Adult Melyridae (Coleoptera) associated with shoots of Pittosporum crassifolium infested with nymphs of pittosporum psyllid, Trioza vitreoradiata (Hemiptera: Triozidae). The beetles probably feed on honeydew. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 285S]

Adult mealybug ladybird, Cryptolaemus montrouzieri (Coleoptera: Coccinellidae). © Plant & Food Research. [Image: 2863]

Adult variable ladybird, Coelophora inaequalis (Coleoptera: Coccinellidae), about 5 mm long. Creator: Tim Holmes. © Plant & Food Research. [Image: 2862]

Pittosporum psyllid damage to leaves can make specimen trees and hedges unsightly and can lower the value of branches grown as foliage for florists or pot plants grown for sale.

People growing Pittosporum pot plants or for sale as foliage can reduce risk of psyllid damage by removing any nearby alternative host plants, especially Pittosporum crassifolium.

Risk of leaf damage can also be reduced by growing less-favoured plant species or selections. Where plants need to be trimmed, e.g. hedges, try to do this when the subsequent new growth will not coincide with the times when many adult psyllids are active. Avoid generating new shoots in spring, early summer and in the autumn. Try trimming in midsummer when new growth can harden quickly and become unsuitable for the psyllid.

Natural enemies of psyllids, such as lacewings, ladybirds and parasitoids, can greatly reduce populations of juvenile psyllids, though they will not get rid of existing leaf damage.

Insecticides will also not get rid of existing leaf damage. If insecticides are needed, try to use those that do least harm to natural enemies. If plants are susceptible to psyllid damage, apply the insecticide at the first signs of adult activity when new leaves are appearing. If the plant is growing rapidly, several applications may be needed. Spray to cover the upper and undersides of leaves.

Male behaviour

While looking at adult psyllids collected for photographs for this factsheet, it was observed that the males frequently pressed the end of their abdomens against whatever they were standing or walking on. Closer observation showed that they had opened up the top side of their external genitalia and rubbed part of this on various surfaces. Is this a female attractant or an arrestant? Do male psyllids of other species exhibit similar behaviour?

Why are some nymphs hairy and others smooth?

Another area for study is the variable hairiness of the upper, or dorsal, side of pittosporum psyllid nymphs. There is scope for comparing the proportions of hairy and hairless nymphs on the different species of host plants, and breeding the psyllids to see if hairiness or hairlessness are dominant or recessive characters.

More biological information

More detailed information about the life history of this psyllid can be found in the 1949 paper by Carter.

Metal outdoor signs are available for placement in reserves, Regional and National parks, urban parks and school grounds. They can be bought from Metal Images Ltd, www.metalimage.co.nz/products/botanic-labels. The Bug Signs are listed near the bottom of the ‘Fauna Species list’. The signs come in two sizes, 100 x 200 mm, 194 x 294 mm. The signs can be bought ready mounted on a stand that needs to be ‘planted’ in the ground, or they can be bought unmounted with holes for fixing into your own mounts.

Signs for the Pittosporum psyllid are best placed by Karo, Pittosporum crassifolium, tree with leaves showing typical psyllid damage. Psyllid leaf damage in Karo can be encouraged by trimming the tree in summer to encourage new growth. Other species of Pittosporum may also be suitable if their leaves exhibit psyllid damage.

Large Bug Sign (5007) for Trioza vitreoradiata, Pittosporum psyllid, 194 x 294 mm. Creator: Metal Images Ltd. © Metal Images Ltd & Entomological Society of New Zealand. [Image: 1L19]

mall Bug Sign (5007) for Trioza vitreoradiata, Pittosporum psyllid, 100 x 200 mm. Creator: Metal Images Ltd. © Metal Images Ltd & Entomological Society of New Zealand. [Image: 1L1A]

Carter MW 1949. The Pittosporum cherid, Powllia vitreoradiata Mask. New Zealand Journal of Science and Technology, Section B 31(2): 1-42.

Martin JH, Malumphy CP 1995. Trioza vitreoradiata, a New Zealand jumping plant louse (Homoptera: Psylloidea), causing damage to Pittosporum spp. in Britain. Bulletin of Entomological Research 85: 253-258.

Plant-SyNZ: Invertebrate herbivore-host plant association database. plant-synz.landcareresearch.co.nz/.

Sommerfield KG 1984. Greenhouse and ornamental pests. In: Scott RR ed. New Zealand pest and beneficial insects. Canterbury, New Zealand, Lincoln University College of Agriculture. Pp. 65-92.

Tuthill LD 1952. On the Psyllidae of New Zealand (Homoptera). Pacific Science 6(2): 18-125.

Valentine EW 1967. A list of the hosts of entomophagous insects of New Zealand. New Zealand Journal of Science 10(4): 1100-1209.

Pam Dale for psyllid identifications and information about the psyllid

Peter Workman for information about the psyllid, especially its natural enemies, and photographs

The New Zealand Institute for Plant & Food Research Limited (Plant & Food Research) for permission to use photographs

1 October 2019, NA Martin. Recognition: ‘continually twitches’ changed to ‘often twitches’.

1 April 2018. NA Martin. Bug signs updated

1 August 2017. NA Martin. Photos added of high stem infestation and psyllid sugars, and moulting.

23 April 2016. NA Martin. Extra photos added to recognition, Honeydew, Natural enemies and Other Images.

11 March 2014. NA Martin. Life stages: added paragraph on walking, jumping and flying. Recognition: added photograph of adult and nymphs of psyllid and whitely puparia on Pittosporum. Natural enemies: revised paragraph on ladybirds, photographs of more predators. Host plants: new photos added.