Citrus are susceptible to a number of serious graft transmissible diseases, which can be symptomless in some rootstock combinations but debilitating when infected buds are budded onto commercially used rootstocks. Infection of nursery trees with a virus/viroid such as exocortis can cause yield reductions of up to 50% and more over time, necessitating removal of the infected trees and replanting. In many cases a small number of infected trees in an orchard will result in widespread infection as the disease is spread through normal pruning and cultural operations.

Auscitrus budwood source trees are subjected to regular testing to ensure freedom from exocortis, psorosis and other graft transmissible pathogens. Grapefruit varieties are immunised with a mild protective strain of tristeza to protect against stem pitting. Strict hygiene procedures are adhered to in tree management, cutting of budwood and extraction of seed.



Graft-transmissible viroids are a serious economic threat to citrus production. Viroid diseases can cause stunting, yield loss and even the death of particular scion and rootstock combinations – yet other varieties may be symptomless carriers.

Find out more on Viroids in Australian Citrus


Graft-transmissible viruses are a serious economic threat to citrus production. Virus diseases can cause stunting, yield loss, developmental abnormalities and even death in particular scion and rootstock combinations – yet other varieties may be symptomless carriers.

Find out more on Citrus Viruses in Australia


Citrus tristeza virus (CTV) is the most devastating viral disease affecting citrus globally.

CTV is a complicated virus and exists in hundreds of different forms known as isolates. Most trees are infected with more than one isolate, and each isolate may contain more than one strain of CTV.

Find out more Citrus Tristeza Virus


Located in the NSW Department of Primary Industries facility at the Elizabeth McArthur Agricultural Institute (EMAI) at Camden, NSW.  

This state-of-the-art facility is available for Auscitrus use through a deed of licence we hold with the Department, an arrangement that has worked well for decades.

This means our indexing team (who are actually NSW DPI employees but funded by Auscitrus) have access to world class facilities and associate daily with some of the leading pathology/virology people in the country.  The Auscitrus indexing program is managed by Dr Nerida Donovan, a world recognised expert in citrus pathology/virology.