Saving the Avocado Tree, One Beetle at a Time

Fig.1. The redbay ambrosia beetle (Xyleborus glabratus) is currently wreaking havoc among avocado crops in Florida. (Credit: USDA, 2012)

Little do guacamole lovers know that two different types of ambrosia beetles -- Xyleborus glabratus and Euwallacea sp. -- and the fungi they carry are terrorizing avocado groves in Florida and California, respectively, where more than 99% of the U.S.’s avocado crop is grown. But fear not, the USDA Agricultural Research Service’s Crop Bioprotection Research Unit is on the case.

Faced with the beetle problem, the team turned to a nontraditional solution. In the early 2000s, certain members of this group patented a fungal foam that delivers entomopathogenic fungi that attack subterranean termites from the inside out. The team hopes the same entomopathogenic fungi will be successful in the fight against the avocado’s biggest threat.

From lab to field

Alejandro Rooney, research leader for the unit, said his team’s mission is to develop environmentally friendly ways to control insect pests and fungal diseases affecting crops. The interdisciplinary team - made up of Rooney, a microbiologist , a biocontrol entomologist , and a formulation chemist - do their best to make their technologies field-ready, working from discovery and development to formulation and application. So when these ambrosia beetles began spreading their harmful fungus in the groves along the coasts, the unit looked back at a past success they had with the termite foam.

Data is currently rolling in from field tests in Florida, where USDA-ARS is collaborating with a team from the University of Florida at Homestead. Rooney said trials should begin in California this summer. But, he’s expecting a difference in the way the foam reacts to the areas’ climate.

“Avocado production in California is really in the dry part of the state. You’re talking about like from Pasadena down through San Diego. Whereas in Florida, it’s the opposite. You’re talking about a subtropical climate where it’s raining constantly and humidity’s not an issue...,” Rooney said. “It’s not just a matter of seeing whether or not we can actually kill the insect with foam - there is that - but it’s also a matter of trying to formulate it in such a way that it’s going to be effective in the field. Because, you know, things you develop in the lab aren't necessarily directly translatable to the field, at least, not immediately, anyway.”

New finds in culture collections

And as part of the discovery process, Rooney and his team will turn to scientific collections. Formerly the curator of bacteria and the director of ARS’ culture collection, Rooney said they have been using a newly established microbial biological control agent collection and a recently transferred collection of approximately 3,000 cultures from a USDA-ARS foreign research unit located in Montpellier, France.

“Some of those are some new species that we've never looked at before. Others are some strains of existing species, but we think that maybe these are superior strains that can be used in new ways,” he said.

Keeping on top of the next invasive or destructive species is never an easy task, but innovation and resources like those utilized by ARS’s Crop Bioprotection Research Unit help keep scientists prepared to respond to the next crisis.

As for the avocados, if the tests in Florida and California go well, then the next step is to scale things up so that the treatments can be developed in a commercially viable [economical] way. Though many other variables affect the health of the avocado supply, this is a welcomed assurance that USDA scientists are working to make sure that an avocado shortage won’t ruin lunch.



References:

Crop Bioprotection Research. (n.d.). USDA-ARS online. Retrieved from http://www.ars.usda.gov/main/site_main.htm?modecode=50-10-05-05.

Fungal Foam Seeks to Destroy Termites. (Aug. 31, 2007). USDA-ARS online. Retrieved from http://www.ars.usda.gov/is/AR/archive/sep07/termites0907.htm?pf=1.

Fungal Foam Tested Against Avocado Threat. (Aug. 5, 2013). USDA-ARS online. Retrieved from http://www.ars.usda.gov/is/AR/archive/aug13/avocado0813.htm.

ARS Culture (NRRL) Collection (2014). USDA-ARS online. Retrieved from http://nrrl.ncaur.usda.gov/.

Glossary

entomopathogenic
Insect-killing
culture collection
Repositories of microbial specimens, including various strains (a genetic variant or subtype) of microorganisms like viruses, bacteria, or fungi.