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Xylella fastidiosa has many names

This bacterium can infect many host plants and the disease can have different names depending on the host. A common name for this disease in grapevines is Pierce’s disease.

How it harms plants

 Xylella fastidiosa multiplies in the water transport system in plants, blocking and damaging it. This impairs water movement within the plant, causing leaf scorching and wilting. 

Symptoms can vary between hosts and in some cases, plants may have no symptoms (asymptomatic). It is important to keep in mind that symptoms can be confused with water stress, nutrient deficiencies, frost and herbicide damage.

Signs to look for in grapevines

  • The characteristic symptom is leaf scorch that is observed in late summer. This includes marginal leaf scorch that is surrounded by a yellow halo.
  • The outer leaf area may dry suddenly while the rest of the leaf remains green.
  • The leaf may drop leaving only the petiole attached to the plant.
  • Diseased plants tend to mature irregularly with patches of brown and green tissue.
  • Flower clusters on infected grapevines may set berries but these usually dry out before reaching maturity.
  • Susceptible grapevine cultivars can die within 1 to 2 years of the initial infection.

General symptoms

Plants infected with Xylella fastidiosa can show:

  • scorched leaves, browning, leaf-loss
  • stunted shoots
  • reduced fruit size
  • over time, dieback and death of the plant.

Keep in mind that these symptoms can also be a sign of other plant diseases already present in New Zealand.

If you have found signs you think might be Xylella fastidiosa on host plants:

  • photograph your plant
  • call 0800 809 966.

Photos to help you identify Xylella fastidiosa

All pictures courtesy of Diego Olmo, IRFAP, Spain.

Symptoms on grapevines

Typical “matchstick” symptom of Xylella fastidiosa infection on grape- Pierce’s disease. Diego Olmo, IRFAP, Spain.

Typical “matchstick” symptom of infection on grape (Pierce’s disease).

Typical “green island” symptom of Xylella fastidiosa infection on grape- Pierce’s disease. Diego Olmo, IRFAP, Spain.

Typical “green island” symptom of infection on grape (Pierce’s disease).

How Xylella fastidiosa spreads

Xylella fastidiosa is spread by the movement of infected plant material and sap-sucking insects such as spittlebugs and sharpshooters. It could travel internationally on infected nursery stock or illegally imported plant material.

The Ministry for Primary Industries (MPI) has strict measures in place to limit the chances of infected nursery stock or insects coming through the border. The meadow spittlebug (Philaenus spumarius), which is a key vector in Europe, is present and widely distributed in New Zealand. In addition, there are many native local insects that could potentially spread Xylella fastidiosa.

The damage the bacterium has done overseas

Overseas, Xylella fastidiosa has caused devastating diseases in crops like grapes, olives, prunus, and citrus. These are important to New Zealand's economy.

It goes by many names depending on the host, such as bacterial leaf scorch, Pierce's disease, phony peach disease, olive quick decline syndrome, and citrus variegated chlorosis.

This bacterium has had a devastating impact in Italy, where it killed 1,000-year-old olive trees and decimated olive production, costing billions of Euros on production losses and damages. In California, Pierce’s disease significantly impacts grape production, costing around $104 million annually due to reduced yields and control measures.

Global distribution of Xylella fastidiosa

This map is from the EPPO Global Database

Global distribution of bacterial leaf scorch

The areas coloured orange indicate where Xylella fastidiosa has been detected. A yellow dot means it is present and a purple dot means it is transient in those locations.

Note, the information on this page is a summary of this disease's global distribution and potential impacts to New Zealand.

Find out more about Xylella fastidiosa (bacterial leaf scorch)

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