Leafhoppers – also known as tree hoppers, plant hoppers or Jassids – are a very diverse group of small insects having many different species associated with Eucalypts. All leafhoppers are sapsuckers which feed on the leaves, twigs and branches of the host tree. Some species live in colonies of mixed stages while other species are solitary. Several species are attended by ants which collect the sugary secretions (honeydew) produced by the leafhoppers. An airborne fungal disease – sooty mould (Fumago vagans) – is often associated with the honeydew.
Above: Leafhopper adult, top right, 14mm long and stage five nymph
Leafhoppers are tent-shaped insects which resemble small cicadas. Some species are green in colour - the Green Leafhopper (Siphanta acuta); some brown - the Spiny Leafhopper (Sertorius australis) and some black with white,red or creamy-yellow markings -Jassids (Eurymela spp.). The nymphal stages resemble the adults but wings are absent.
The most commonly found leafhopper on Eucalypts is the Common Jassid (Eurymela fenestrata). This is one of the larger leafhoppers, the adult being approximately 12-15mm in length. Early instars are black with faint red markings, later instars black and red, with red and metallic blue underneath. Adults are black with creamy markings on the wings and red and metallic blue underneath (metallic colours fade rapidly after death).
Above: Nymphs of the Common Jassid
Above: Damage to stems by the Common Jassid
Other less commonly seen leafhoppers on Eucalypts are the Green Leafhopper and the Spiny Leafhopper. The Green Leafhopper is a small bright green insect approximately 8-10mm in length (adults) with wings folded in a characteristic triangle high above the body. The Spiny Leafhopper is a small brown insect approximately 8mm in length. Adults have a sharp spine either side of the head.
Little is known of the life history of most leafhoppers. Eggs are usually laid in slits in the bark on branches or twigs. All nymphal and adult stages feed by sucking the sap of the host tree.
Above: Leafhopper lifecycle; Adult is 14 mm long
The young nymphs go through a series of moults to become fully winged adults. There are five nymphal stages. Usually there is only one generation per year and nymphs may be seen from mid-October through to March or April.
Adults and nymphs of all stages of the Common Jassid occur together in colonies. Green Leafhopper and Spiny Leafhopper adults are solitary but the nymphs usually gather together on twigs or young shoots.
When disturbed, adults either fly or hop away. Nymphs can do neither and, if disturbed, move quickly around to the other side of the twig or leaf.
Leafhoppers suck the sap from young twigs and branches. Some species cause only minor damage but other species have toxic saliva which causes the death of plant tissue. A few species are vectors of plant viruses.
The Common Jassid is occasionally a serious pest of forest trees (the other species mentioned above are not regarded as pests). At times hundreds of these leafhoppers may be seen clustered together on the trunks and branches of Eucalypts and anything else nearby – though they only feed on Eucalypts.
Common Jassids produce large quantities of honeydew and consequently outbreaks of sooty mould are common with severe infestations.
Common Jassids are also always attended by ants which collect and feed on the honeydew.
Leafhoppers in general are regarded as minor pests of Eucalypts. Attack is often seasonal and the hoppers eventually disappear without any treatment.
All stages of leafhoppers are preyed upon by a wide range of animals including birds (such as thornbills), tree-climbing lizards, spiders, hoverflies, assassin bugs, lacewings and ladybird beetles.
Eggs and nymphs are parasitised by tiny Chalcid wasps and are also occasionally attacked by predatory mites and fungal diseases.
Large infestations of the Common Jassid are usually well controlled by natural enemies. Other leafhoppers are only rarely seen in large numbers.
If infestations are considered severe enough to warrant action being taken, chemicals may be used. Small trees may be sprayed with a contact spray such as endosulphan, carbaryl or maldison. Severe infestations on large trees can be controlled by injecting the trunk with dimethoate, however this method should only be used in extreme circumstances, for example, when valuable genetic material is at risk.
From October through to March and April.
On branches, twigs and young adult leaves.
Small, tent-shaped insects that hop or fly away if disturbed or run around to the other side of the branch or leaf. In the case of the Common Jassid (Eurymela fenestrata), look for early instar nymphs clustered on young adult foliage and later nymphs (black and red) and adults on the twigs and branches.