Exocortis, sometimes referred to as scalybutt, was a major disease of australian citrus trees on trifoliate orange rootstock in the 1940s and 50s, but is now rarely seen because of the use of pathogen-free budwood from the auscitrus budwood scheme.

Citrus exocortis viroid (ceVd), can infect all varieties of citrus but is symptomless in most.

Disease symptoms develop when infected budwood is grown on susceptible rootstocks like Poncirus trifoliata, rangpur lime, and sometimes Swingle citrumelo and citrange.

No symptoms of exocortis are seen on trees grown on rough lemon, sweet orange and mandarin rootstocks.

This Primefact covers the following topics:

• Symptoms
• Disease source and spread
• Disease verification
• Disease control