Over the last decade, Florida’s famous citrus industry has been battered by a disease called citrus greening, which has destroyed acres of crops and cost untold billions in revenue.
Combining expertise in soil, plant pathology, entomology and chemistry, a Colorado State University team will research how the disease propagates, and how it can be stopped. Their efforts are supported by a $1.2 million gift from Cutrale, one of the largest suppliers of orange juice in the world.
Citrus greening is caused by a bacterium transmitted from tree to tree by the Asian citrus psyllid, an insect that feeds on the leaves and stems of citrus trees. Diseased trees produce green and stunted fruit; eventually, the bacterium, Candidatus Liberibacter asiaticus, can kill entire groves of trees.
The CSU team is led by Thomas Borch, a professor in the Department of Soil and Crop Sciences with joint appointments in civil engineering and chemistry. Together, the researchers will assess how effective pesticides have been at controlling the psyllids, and whether these insecticides could be distributed differently to better manage the psyllid populations.
“We know that the insects transfer the pathogens to the citrus trees,” Borch said. “So controlling the insects is vitally important – prevention is the key since there is no cure for citrus greening.”
Borch and colleagues also want to know if the psyllids have become resistant to pesticides. Better understanding this resistance will help entomologists, including team member Paul Ode, integrate other techniques like parasitic wasps and mating disruption approaches. Ode is a professor in the Department of Bioagricultural Sciences and Pest Management, part of CSU’s College of Agricultural Sciences.
Identifying how the insects move from grove to grove, and whether and how infected psyllids are likely to disperse, will also be important to the study, according to Ode. Some of the psyllids come from abandoned citrus farms that remain in close proximity to active citrus operations. It is yet unclear whether storms like Hurricane Irma have worsened the impacts of citrus greening by contributing to its spread.