If you want to study ambrosia beetles in a laboratory, you’ve got to have a way of not only keeping them alive but also encouraging them to thrive and reproduce. The simplest way of raising beetles in captivity has been to cut pieces of wood and place them in a jar with the beetles, effectively reproducing their wild habitat. But there are problems with this approach. The University of Florida’s Forest Entomology Lab has recently experimented with a new method that could become common.

The idea is to replace wood with a material that can be standardized, easily sterilized, customized to suit a particular experiment, and easily collect beetles from.

“Wood’s a little messy to deal with,” says Dr. James Skelton, a scientist involved in the lab’s experiment with a new method. “Opening it up, especially these xyloborus beetles that make extensive galleries, it’s hard to open that up without smashing the beetles inside.”

The new alternative involves mixing agar and sawdust with milk protein casein, wheat germ oil and a salt mixture. It forms a soft, wood-like substance that can be poured while hot into a vessel, where it solidifies.

The Carillo Lab at the University of Florida conducted experiments with this method for years, publishing a number of papers and establishing the model now being used by the UF Forest Entomology Lab. The Carillo Lab, in turn, was inspired by early experiments by Dr. Louela Castrillo of USDA.

Sawyer Adams, the Forest Entomology Lab’s manager, helped make the lab’s first batch of Castrillo media and will be producing it for the lab going forward. She says that the substance is simple to make.

“Overall a takes few hours,” Adams says. “You mix it up, autoclave it, pour it, and then let it dry in the hood for week.”

Making a beetle media from agar and sawdust is nothing new — the lab has used that form of media for years as a sort of temporarily housing to keep beetles alive on plates during shipping. Few species thrived in it for long. The new addition of milk protein, wheat germ oil, salt and trace minerals takes a page from other areas of entomology where those substances are used to improve the nutrition of lab-reared insects. But it is something of a mystery as to how it is helping ambrosia beetles, which are thought to feed exclusively on fungus that they farm in their galleries.

“It seemed a little strange to me because the whole thing about ambrosia beetles is that they eat only their fungus,” says Dr. Skelton. “So why would you want to make a media that has a bunch of stuff in it that’s nutritious for beetles if they aren’t eating the media? It seems like you would want to make a media that’s good for fungus with malt extract or whatever. But for whatever reason this media works really well.”

It isn’t clear how or whether the added nutrition reaches the beetles. Are they eating the media directly, or are the nutrients mediated through the fungus? We don’t know yet.

The results from the Castrillo media impressed scientists at the UF Forest Entomology Lab very quickly.

“It’s easy and it’s fast,” says Skelton. “We’re producing dozens of progeny per initial beetle in a month. It’s like Drosophila, almost. The galleries looked nice and clean with tons of ambrosia growing in there. I think it could be a super powerful tool for testing hypotheses about what maintains particular relationships between certain fungi and certain beetles. Whether there is any adaptive value to beetles having multiple symbionts or one symbiont.”

Ambrosia beetles can be a powerful model for the study of evolution. With thousands of species radiating from multiple instances of convergent evolution, combined with their rapid rates of reproduction and close relationships to specific fungi and plants, ambrosia beetles allow scientists to test ideas about evolution far faster than is possible with mice and in more complex situations than using fruit flies.

“With this method, it’s easier [than with wood] to get everybody out,” says Dr. Skelton. “And presumably we can introduce all sorts of things to the media. Control the amount of nitrogen that’s available or phosphorus or carbon… whereas with wood it’s got what it’s got.”

With the coming of summer, the UF Forest Entomology Lab has two big things to look forward to. An increase in observable beetle activity, and the opportunity to step away from the classroom and lab to find out what’s happening in the field.

PhD candidate A. Simon Ernstsons will spend three months organizing field work in China that is critical to the future of the lab and for establishing a better way of preventing destructive outbreaks of forest pests. Ernstsons will be spearheading the lab’s new sentinel garden project aimed at identifying future pests before they even arrive in the US.

Ernstsons must find his way around several regions of rural China, obtain hundreds of trees of American commodity species that are rare in Asia, transport them to remote planting sites, then monitor them for damage by local insects. Some of the trees will be deliberately stressed to simulate the effects of flooding and drought.

“Then we have a really important data point where we know something potentially dangerous is in a certain area,” Ernstsons says. “We can then feed back that information back to USDA [division of Animal and Plant Health Inspection Service] and it can influence things like bio-security measures, phytosanitary control, that sort of thing.”

Sentinel gardens are a relatively new concept already being explored between France and China by Dr. Alain Roques and his team at the French National Institute for Agricultural Research. There is currently no equivalent involving the United States, though botanical gardens may notify one another when they notice a new pest on an exotic tree.

Organizing an experiment like this is not an easy task. Layers of government bureaucracy, cultural differences, and language barriers make it difficult to design and monitor an experiment involving hundreds of trees that are scarce in China. Fortunately, Ernstsons (who speaks five languages, including Mandarin), has experience with a small-scale pilot project for the lab last summer.

“Imagine trying to arrange two hundred trees to be delivered to a village on the side of a mountain in the middle of rural China, how would you go about doing that and how difficult do you think would that be?” Ernstsons asks. “That’s my experience. Going out and doing those kinds of things with local scientific collaborators, but also collaborators for logistics, things like sourcing and buying the trees.”

The work is funded by grants from USDA’s APHIS through the Plant Protection Act, section 7721.

As invasive beetles including the emerald ashborer and the Asian long-horned beetle continue to destroy American trees, could those infestations have been prevented by sentinel gardens? Ernstsons believes so.

“We certainly could have known well in advance and tried to put measures in place. Once it’s arrived we’ve seen again and again that ninety nine percent of the time it’s a losing battle.”

Sawyer Adams, left, with Allan Gonzalez, right. Photo by Jackson Landers.

The Hulcr Lab now has a new lab manager.

Allan Gonzalez, our talented out-going manager, is moving to South Africa to begin graduate work at the University of Pretoria.

With a background in community ecology before joining the Hulcr Lab, Gonzalez intends to use his new ambrosia beetle expertise to study the polyphagous shot hole borer (Euwallacea whitfordiodendrus) and the fungus associated with it. An outbreak of the invasive beetle has exploded across South Africa and has devastated urban vegetation in many cities.

“I want to see how it’s impacting native trees in the Eastern Cape of South Africa,” Gonzalez says.

In addition to his duties managing the lab, Gonzalez also contributed to several papers as a co-author and spearheaded research for a pest management company.

The lab welcomes our new manager, Sawyer Adams, who will graduate from the University of Florida this spring with a botany degree. She began work at the Hulcr Lab in March in order to begin a transition alongside Gonzalez. Adams brings a new type of expertise into the lab as our only botanist.