What is in this article?:
California promoting bio control of Asian citrus psyllid in urban areas of southern California.
Mark Hoddle, an entomologist with the University of California, Riverside studies Asian citrus psyllids and Tamarixia radiate in quarantine at his UC Riverside lab.
A climate match of 70 percent between the two regions was enough for Hoddle. He collected Tamarixia from a number of locations, figuring that the biological diversity of insects collected would diversify the samples and allow reproducing populations to adapt over time to the southern California region.
Not only would wasps be released in Los Angeles and the Inland Empire, where conditions range from coastal to hotter and drier in Riverside and San Bernardino counties, but they would have to survive the extreme heat of Imperial County, where summertime temperatures can exceed 120 degrees.
To date more than 160,000 parasitic wasps have been released in over 400 locations spanning 350 zip codes, 64 cities and six counties in southern California. Those counties are: Los Angeles, Orange, San Bernardino, Riverside, San Diego and Imperial.
Hoddle is encouraged by the success of the program, and moreover, by the biological success of the wasp. Since it was first released, it has developed its own breeding populations and has been discovered as far as eight miles away from initial release sites, indicating that it is quite mobile.
What makes the Tamarixia attractive to entomologists is its exclusive diet of ACP. Another benefit of the Tamarixia is it reproduces more females than males. The females tend to live 12-24 days and will produce between 166 and 300 eggs over their lifetime.
The Tamarixia wasp attacks the third, fourth and fifth instars, or development stages, of the ACP nymph. Earlier nymph stages become feeding grounds for female Tamarixia as they literally suck the blood from developing nymphs, killing them immediately.
This host feeding technique is quite common with the Tamarixia, as females feed to provide protein and other nutrients for the eggs they will eventually lay under the developing ACP nymphs that they have not previously parasitized.
Hoddle said he and his technicians in the quarantine lab at UCR have witnessed female Tamarixia attack adult psyllids, stinging them to death.
“It’s not very common, but I’ve seen it and my technicians have seen it in the quarantine cages a few times,” he said.
Hoddle stresses that the psyllids contained in his quarantine lab have all tested negative for HLB. That was one of the conditions established prior to setting up this lab, he said.
What makes the psyllid so deadly to citrus, according to Hoddle, is in how they feed. He likes to call the ACP “flying syringes.”
Psyllids are obligate phloem feeders, meaning they are genetically required to feed on the phloem in citrus trees and plants in order to survive. They do this through a needle-like feeding tube. Their bodies act as a syringe, drawing phloem into them. If the HLB bacteria are present in the tree they are feeding upon, they can then transport that bacteria to another tree, where it can be transmitted through the feeding process.
This is in large part the reason for California’s “search-and-destroy” attitude towards finding trees with HLB. While only one tree has been discovered in the state thus far, officials fear there are many more that have yet to display clear symptoms of HLB. This is why controlling the spread of the ACP, particularly in the San Joaquin Valley where small numbers have been discovered, is so critical for the citrus industry.