October 10, 2017
I recently heard an interesting presentation on National Public Radio on citrus greening, a disease that is decimating citrus fruit trees in Florida and other areas. Not only has this year's Florida citrus crop been hit hard by Hurricane Irma, particularly in the southern part of the state, this bacterial disease is doing significant damage as well, infecting 80 percent of Florida's leading crop. Florida is not the only state affected. Georgia, Louisiana, South Carolina and Texas have citrus greening too. Dozens of countries around the world are losing their crops as well, although Australia's and the Mediterranean countries' citrus crops are not infected. Although the psyllid has been found in California, very few trees have been discovered with the infection. California's Agriculture Department has implemented quarantines to contain and reduce the spread of the disease.
The citrus greening bacterial disease is spread by the Asian citrus psyllid, a tiny flying insect that sucks plant juices for food. It goes from leaf to leaf, tree to tree, infecting every time it feeds. The disease incubates in the roots, then spreads through the tree, slowing the flow of nutrients. This results in stunted and sour fruit that is unmarketable and causes the death of the tree within three to five years. Once a tree is infected there is no cure. Infected trees have to be removed and destroyed.
Researchers have been working on this for years and are getting close to a solution. They are modifying and introducing psyllids that are incapable of spreading the disease, just as they modified mosquitoes to reduce the spread of malaria. They are testing antibiotics. They are breeding disease-resistant varieties, but this takes years. They are exploring ways of making the trees less attractive to the psyllids. They are also looking at genetic modification to save the $10 billion industry.
Farmers are trying various fertilizer regimes in hopes that strengthening overall tree health will help the tree resist the infection. They are also using beneficial insects that can parasitize the psyllids, killing them. They use pesticides to manage insect populations.
While we don't grow citrus here in Northern Nevada, this disease has greatly impacted orange juice, grapefruit, lime and lemon production, so it does affect anyone who likes orange juice or other citrus fruit. I trust science will find a solution. We don't want to lose the US citrus industry.
JoAnne Skelly is Associate Professor & Extension Educator, Emerita, University of Nevada Cooperative Extension. She can be reached at firstname.lastname@example.org.