Researchers from the Boyce Thompson Institute, the U.S. Department of Agriculture Agricultural Research Service (USDA-ARS) and the University of Washington (UW), led by Michelle Heck, investigated a seemingly unlikely source of bio controls for HLB: neuropeptides found in the insect that carries the disease-causing bacterium.
Citrus Greening Disease, also known as Huanglongbing (HLB), is a bacterial infection of citrus trees that results in small, misshapen and sour fruits that are unsuitable for consumption, ultimately killing the tree. Because there is no cure, HLB is a major threat to the $10 billion citrus industry in Florida, where it was first detected in 2005, and to the $7 billion industry in California, where it appeared last year.
The root cause lies with Asian citrus psyllids (Diaphorina citri) infect citrus trees with Candidatus Liberibacter asiaticus (CLas) bacterium by feeding on their leaves and stems.
Laura Fleites, a USDA T.W. Edminster Research Associate in Heck's group at BTI, focused on neuropeptides because they function as hormones in hemipteran insects—a class that includes psyllids, aphids, whiteflies, shield bugs and other crop-plaguing species—to regulate growth, development and other biological functions. Moreover, other studies have shown that analogs of insect-derived neuropeptides kill pea aphids, and insecticides based on the kinin family of neuropeptides have been developed.
"If we could develop an insecticide that is specific for Asian citrus psyllids based on one of the insect's own neuropeptides, then we could protect citrus trees from the insect that spreads CLas," Heck said. "Citrus greening disease is devastating our citrus industry, and we need to develop new ways for our citrus growers to control it."