Xylella and exotic vectors
PLANT PEST
Xylella (Xylella fastidiosa)
and exotic vectors
Exotic to Australia
Features: A bacterial disease that causes scorched leaves,
browning and loss of leaves, stunted shoots, reduced fruit
size, dieback and death of many types of plants
Where it's from: Americas originally, now also in Europe,
Taiwan, Israel, Iran and the Caribbean
How it spreads: Importation of infected plants and plant
material; local spread through insect vectors
At risk: Over 350 native, commercial and ornamental plant
species, including wine grapes, olives and fruit and nut trees
Scorched leaves are a common symptom of the bacterial
disease xylella which can infect hundreds of plant species.
John Hartman, University of Kentucky, Bugwood.org
Keep it out
Xylella [pronounced zy-lella] tops the list of Australia’s National Priority Plant Pests because it causes devastating disease in many species of plants, including many of the crops that we rely on for food and fibre, and there is no cure.
The bacteria (and related subspecies) does not impact human health but kills plants by damaging the water conducting system (xylem) in plants, which shows as leaf scorching.
Xylella infection has several names depending on the plant that’s affected. Commonly it is known as bacterial leaf scorch, but in grapes it is known as Pierce's disease, California vine disease and Anaheim disease. In olive it’s known as olive quick decline, in peach it is called phony disease, and in citrus—variegated chlorosis.
Xylella is spreading around the world, causing significant problems as it kills crops and other plants. In recent years, the Puglia region of southern Italy has seen xylella devastate historically and economically important olive trees and orchards.
The disease could arrive in Australia through:
- importation of infected plants or planting material such as budwood, cuttings and rootstock
- insects infected with the disease. Two exotic plant feeding insects, meadow spittle-bug and the glassy winged sharpshooter, are also the subject of biosecurity measures to keep them out of Australia.
Importing goods
To keep xylella out of Australia, never ignore Australia’s strict biosecurity rules.
Import shipments may need to be treated and certified, so before you import, check our Biosecurity Import Conditions system (BICON).
What to look for
- Scorching of leaves on plants that advances through the tree or vine.
- The meadow spittle-bug and the glassy winged sharpshooter. Spittle-bugs are usually less that 13 mm but may be up to 27 mm; while glassy winged sharpshooters are 2-30 mm but average 13 mm.
Where to look
Importers
The most likely way that xylella could make it to Australia is in infected plant material, including cut flowers, nursery stock, fruit and vegetables, or in infected insects.
Growers and home gardeners
- Check your plants frequently for any unexplained leaf scorching.
- Keep an eye out for the exotic insects that can carry the disease.
Damage to crops
Xylella causes disease in more than 350 different plant species including fruit and ornamental trees. It affects agricultural crops like:
- citrus
- cherry
- blueberry
- nursery
- nuts
- summerfruit
- grape
- olive
- avocado
- pear.
What to do
- If you think you’ve found symptoms of xylella or one of the exotic insect vectors:
- do not disturb the plant or bug (this may be as simple as closing the doors on a shipping container)
- take a photo
- collect a sample of the infected plant or insect, if possible to do it without disturbing it.
Read the detail
- Plant Health Australia: Pierce’s disease
- Plant Health Australia: bacterial leaf scorch and the glassy winged sharpshooter
- Plant Health Australia: Citrus variegated chlorosis
- Read about the International Symposium on Xylella fastidiosa
- Download the National Xylella Action Plan 2019-2029