Ever heard of huanglongbing? While more commonly referred to as citrus greening disease, huanglongbing (HLB) is threatening your favorite morning beverage (okay, orange juice, not coffee) and has gathered a lot of agricultural media coverage in the past few years. Now new research on the bacterium, which is transmitted by an insect called the Asian citrus psyllid and ruins oranges and other citrus fruits, highlights how climate change is impacting the spread of this pathogen.
The study was published recently in the Journal of Applied Ecology from researchers at Virginia Tech, led by Rachel Taylor of the Animal and Plant Health Agency (APHA) in the United Kingdom. It aims to provide suggestions for how to improve crop management based on a compilation of suitability maps that the researchers developed.
Because citrus greening transmission depends on temperature (for both the pathogen and insect vector), the team was able to determine which areas were the most vulnerable to the disease. "Our suitability maps can be used to underpin risk-based surveillance and prevention to ensure resources to fight citrus greening are applied in the best locations," Taylor said. The team then analyzed how thermal environmental conditions affect transmission and in turn concluded recommendations for implementing surveillance and prevention practices.
The model estimates that host plants are the most vulnerable when temperatures are between 16 and 33 degrees Celsius, though the sweet spot for transmission hovers at around 25 degrees Celsius. The suitability maps clearly show the correlation that temperature has had with infection out of the laboratory and in the fields. Many regions around the world that experience temperatures within this range for at least half if not more of the year have had the worst struggles with the disease, including Brazil and South-East Asia.
However, there are some citrus-growing regions, such as California and the Iberian Peninsula, that experience this temperature range and have yet to be affected by HLB. “In these areas known for high citrus production,” reports Science Daily, “preventing the establishment of the disease vector through increased surveillance and management may help prevent the devastating effects that citrus greening has had on other growers.”
"Although the approach is fairly simple, we've shown in other systems that we can make surprisingly accurate predictions," said coauthor Leah Johnson, assistant professor in Department of Statistics in the College of Science at Virginia Tech. "We hope that this model can be a useful planning tool for growers and policymakers dealing with HLB," said Johnson.
Sources: Science Daily, Journal of Applied Ecology
