Dodonaea yellows

Dodonaea yellows is a debilitating plant disease characterized by systemic infection of the host tissue caused by phytoplasmas. These prokaryotic pathogens reside in the plant phloem, disrupting the translocation of photoassimilates and essential nutrients, which ultimately leads to a severe decline in the plant's physiological functions and vigor.

The primary host for this condition is the Dodonaea species, particularly Dodonaea viscosa. This disease poses a significant threat to ornamental nurseries and landscape plantings, where the loss of aesthetic value is often total. Once a plant is infected with phytoplasmas, it typically remains a permanent reservoir for the pathogen.

Symptoms of the disease are diverse and include severe chlorosis (yellowing) of the leaves, stunted plant growth, and proliferation of auxiliary buds. This proliferation results in a dense, bushy appearance known as "witches' broom" due to the abnormally shortened internodes. As the disease advances, the plant's root system weakens, and the plant eventually fails to thrive.

Transmission occurs primarily through the activity of sap-sucking insect vectors, most notably leafhoppers. These insects acquire the phytoplasma while feeding on infected plant sap and transmit it to healthy hosts during subsequent feeding cycles. Environmental conditions that support large populations of these vectors, such as warm temperatures and abundant irrigation, directly correlate with the spread of the disease.

Management of Dodonaea yellows relies heavily on prevention and vector control, as there is currently no cure for phytoplasma infections.

• Implement aggressive insect control programs targeting leafhoppers using systemic insecticides.
• Promptly rogue and destroy all symptomatic plants to reduce the inoculum load in the vicinity.
• Ensure that propagation materials are sourced from disease-free, certified nurseries.
• Maintain weed-free zones around ornamental beds to eliminate alternative hosts for both the vectors and the pathogen.