It is a well-known fact that the future availability of citrus products is threatened by the global spread of huanglongbing (HLB), also known as citrus greening disease.
Knowing which environmental conditions are suitable for disease transmission and where those conditions occur is vital for crop management. A new study published by researchers at Virginia Tech with a team of international researchers in Journal of Applied Ecology investigates the thermal suitability for transmission of citrus greening with implications for surveillance and prevention.
The bacterium responsible for causing citrus greening prevents the formation of commercially viable fruit and is transmitted by an insect called the Asian citrus psyllid.
Both the pathogen and the insect vector have been spreading in recent years, devastating regions famous for high citrus production and threatening the future of the citrus industry. As citrus greening becomes an increasing threat to growers worldwide, the future of the industry may depend on identifying locations that do not have a high risk of production collapse.
Disease transmission dynamics are largely dependent on temperature, both for successful replication of the HLB bacterium and survival of psyllid vectors. The model was built with data collected under laboratory conditions, directly incorporating the effects and limitations of environmental temperature into the estimate of suitability.
The model predicts that successful infection of host plants can occur between 16o and 33oC, with peak transmission at around 25oC. Using this information of the temperature limits for disease spread, the authors were able to make maps of global suitability, showing how many months of the year have temperature conditions that would place citrus groves at risk for infection with HLB. Perhaps unsurprisingly, many regions with nearly year-round suitability for citrus greening include some of the citrus-growing areas hit hardest by the disease, including Brazil and South-East Asia.