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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 summerfruit is phony peach disease.

Summerfruit includes stone fruit like peach, apricot, nectarines, plums, and cherries.

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 summerfruit

  • Stunting of shoots that can be greener and denser than normal.
  • Lateral branches grow horizontally or drop, producing compact-looking trees.
  • Leaves and flowers appear early in the season and leaves remain on the tree longer than on healthy trees.
  • Affected trees produce lower quality and yields with fruit drastically smaller than average.
  • The tree will usually stop producing fruit after 3 years.

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 are sourced from Johnson et al. CABI Agric Biosci (2021) 2:29.

Tree with phony peach disease (foreground) showing advanced petal fall (bloom) and leaf development as compared to healthy trees in the background (still in full bloom and with limited leaf expansion).

Photo A shows fruit on a tree with phony peach disease. They are less mature and ripe than the fruit at the same stage on a healthy peach tree as shown in Photo B. 

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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