- Author: Jeannette E. Warnert
UC Cooperative Extension developed an online interactive map that allows Californians to see how close they live to citrus trees infected with huanglongbing disease, reported Jeanette Marantos in the Los Angeles Times. This information is critical for the more than 60% of Californians who are growing their own backyard orange, grapefruit, mandarin, lime and other citrus trees.
Huanglongbing is an exotic citrus disease that kills every tree it infects. An exotic insect, the Asian citrus psyllid, spreads the disease from tree to tree. If the disease makes its way into California's commercial citrus production regions, it threatens the state's valuable and iconic citrus industry.
Go to http://ucanr.edu/hlbapp and type in your address. If you are inside the red circle — within two miles of a hot zone — UCCE suggests you remove your citrus trees and plant different types of fruit trees, such as peaches, pears, apples or figs, until researchers find a cure. In the yellow circle — within two to five miles of a hot zone — consider replacing your tree with a non-citrus fruit tree or protect your citrus trees. Find detailed information on home citrus management here https://ucanr.edu/sites/ACP/Homeowner_Options/
“When we first started this program back in 2012, I was encouraging Master Gardeners to teach homeowners how to treat their trees [to discourage psyllids, which are the insects that spread HLB],” she said, “but the complaint came back from the Master Gardeners, ‘I treat my trees but none of my neighbors do, so what's the point?'” said Beth Grafton-Cardwell, UC Cooperative Extension entomology specialist and director of the Lindcove Research and Extension Center in Exeter.
Grafton-Cardwell said the threat is serious. HLB disease devastated Florida's citrus industry when it hit in 2005, destroying half of its acreage and production, and pretty much eliminating residential citrus.
The battle against the psyllid in California is being helped by the introduction in 2011 of Tamarixia radiata, a parasitic wasp native to Pakistan, by UC Cooperative Extension biological control specialist Mark Hoddle and his entomologist wife Christina Hoddle.
"We've had psyllid here [in California] since 2008, but we still have a lot of oranges,” Hoddle said. “The disease hasn't swept through California the way it did through Florida, and I believe our biological control program is why. Psyllid populations have decreased by 70% to 80% since our first parasite release in 2011. We haven't wiped out HLB in citrus trees, but we have mitigated the risk.”