Image courtesy of: Denis Crawford
Leafhoppers are small insects from the family Cicadellidae - the largest family in the ‘true bug’ order Hemiptera – and are sometimes known as ‘jassids’. There are at least 22,000 species worldwide, with more than 700 species occurring in Australia. Leafhoppers are usually small, wedge-shaped, cicada-like sap-sucking insects. Some leafhopper species can transmit plant diseases.
Leafhoppers are often confused with the familiar thorn-shaped planthoppers of the family Flatidae - a related but less horticulturally important family. Another group of insects which causes confusion are the treehoppers in the subfamily Eurymelinae. Both these groups are sometimes misnamed as ‘leafhoppers’. Planthoppers and treehoppers are described in this article which will hopefully dispel the confusion.
Leafhoppers are quite difficult insects to control because of their small size and rapid breeding. Your best bet is to keep an eye on your plants so that you can spot leafhopper incursions early.
For example, you could keep an eye out for insects while you are watering your plants. For this to work you will need to know what leafhoppers look like (see Description), so that you know that the insects you observe are actually leafhoppers and not something else. There are other insects which are confused with leafhoppers – it pays to know which is which.
Prevention is always better than cure. There are several things that you can do to prevent leafhoppers becoming a serious problem (see How to Prevent Leafhoppers Appearing). Minor infestations will not seriously damage your plants if those plants are well cared for.
Regular monitoring of your plants will ensure that a major infestation of leafhoppers doesn’t occur ‘overnight’. Managing leafhoppers is much easier if you can catch an infestation in its early stages. Don’t wait for an infestation to build up to unmanageable levels.
If you do see them, spray with Yates Nature’s Way Citrus & Ornamental Spray. It kills them via contact and/or ingestion. For effective treatment, ensure you spray the leaves thoroughly, just to the point of run-off. For severe infestations, repeat sprays may be necessary. If you have large areas to spray, use Yates Pyrethrum Insect Pest Killer Concentrate. Mix in a sprayer and thoroughly apply to foliage.
Image courtesy of: Denis Crawford
Common leafhopper species include the Common Brown Leafhopper (Orosius argentatus), Vegetable Leafhopper (Austroasca viridigrisea) and Yellow Leafhopper (Anzygina zealandica).
Common leafhopper species are wedge-shaped and are about 2 mm to 6 mm long depending on the species. Leafhoppers hold their wings roof-like over the body at rest. Leafhoppers are very active and jump or fly quickly in all directions when disturbed. Leafhopper nymphs are usually smaller in size and wingless.
The Common Brown Leafhopper (Orosius argentatus) is a small motley brown insect about 3 mm long which may transmit serious plant diseases such as Tomato Big Bud. The Common Brown Leafhopper is the only leafhopper which transmits plant diseases in home gardens. The Vegetable Leafhopper (Austroasca viridigrisea) is yellowish-green in colour and about 4 mm long. The Yellow Leafhopper (Anzygina zealandica) is about 6 mm long and yellow.
Planthoppers (Flatidae) are common garden sap-sucking insects. When viewed from the side they are almost triangular and resemble thorns on a twig. They are not leafhoppers, and common species such as the Green Planthopper (Siphanta acuta) are considered to be minor garden pests. The horticulturally significant planthopper species are the Citrus Planthopper (Colgar peracutum) which damages several fruits including citrus, grapes and pawpaw, and the Mango Planthopper (Colgaroides acuminata) which is a pest of citrus and mango.
The taxonomy of the family Cicadellidae has changed recently to include the subfamily Eurymelinae – the ‘treehoppers’ – formerly in a separate family of their own. The most common of these are the Gum Treehoppers (Eurymela spp.), which are occasional pests of young eucalypts in gardens. Gum Treehoppers are cicada-shaped insects about 12 millimetres long and many species are quite colourful with black-and-white patterns and red eyes. They are native insects – if they are on your eucalypts they aren’t necessarily pests.
Leafhoppers, treehoppers and planthoppers all go through a life-cycle of gradual metamorphosis – egg to nymph to adult. Nymphs are miniature versions of the adult form but without wings.
Female leafhoppers usually lay their eggs in slits cut in leaf tissue. The eggs hatch into tiny nymphs which moult and grow larger through four more nymph stages before becoming adults. Leafhoppers usually have a short life cycle of only a few weeks. There are several generations per year, with populations building up through spring, and peaking during summer and autumn.
Common leafhopper species may attack many kinds of plants including:
Leafhoppers are sapsuckers and as they suck sap (usually from leaves) they also inject plant toxins, which causes whitish to yellowish spots (stippling) on the leaves. The spots may form a wriggly pattern or wavy lines. Severe infestations cause leaves to curl, yellow and fall. Seedlings are particularly susceptible.
As well as causing leaf damage symptoms the Common Brown Leafhopper can spread plant diseases such as Tomato Big Bud - a phytoplasma disease also known as ‘greening’. The disease is commonly seen in tomatoes where it causes tomato plants to develop stiff upright stems, enlarged green flower buds, and distorted woody immature fruit. Infected tomato plants have a significantly reduced fruit yield. Common Brown Leafhoppers don’t always carry Tomato Big Bug so the disease is usually only an occasional problem.
The eggs of some leafhopper species are parasitised by tiny wasps. Damsel bugs, ladybirds, lacewing larvae and spiders feed on leafhoppers.