Meet the researcher: Nick Rajtar tenaciously tracks down tree pathogens

By Carolyn Bernhardt

August 14, 2024

a person sitting on a rock in a forest wearing a U of M hat
Nick Rajtar, PhD

Meet Nick Rajtar, PhD, a dedicated researcher specializing in plant pathology at the University of Minnesota. Rajtar’s work focuses on innovative methods for early detection and management of invasive tree pathogens, including harmful fungi and water molds. Rajtar is dedicated to preventing the spread of these destructive species and safeguarding natural ecosystems.

After an upbringing in Ham Lake, Minnesota, Rajtar began his academic pursuit of plant pathology as an undergraduate student at the University of Minnesota. He started working in the corn and soybean lab run by Dean Malvick, PhD, a professor in the Department of Plant Pathology in CFANS. “That got my feet wet,” says Rajtar. “I was helping prepare inoculum for their field tests and learning about molecular techniques relevant to plant pathology. I am very grateful for my time in the Malvick Lab!"

Rajtar recently defended his PhD and began as a postdoctoral associate in the lab of Robert Blanchette, PhD, a professor in the Department of Plant Pathology in the College of Food Agricultural and Natural Resource Sciences (CFANS). "I tell people I wouldn’t have stayed on for my PhD and then postdoc if I didn't really like the lab and love what I'm doing because the work environment is so great," he says. 

researcher sets up a windsock on a pole at the edge of a lake
Rajtar found wind socks to be an effective and inexpensive way to monitor for spores of many pathogens.

Breakthroughs in the lab and field

Rajtar’s PhD research concentrated on enhancing methods for trapping windborne spores and monitoring invasive species. He worked on detecting Heterobasidion root disease (HRD), a fungal infection that spreads through the air and underground roots, making it extremely difficult to eradicate once established. Since fruiting bodies are difficult to find, Rajtar tested various spore traps to optimize detection, balancing cost and accuracy. By sequencing the DNA of trapped spores, he tracked the pathogen’s spread from Wisconsin to Minnesota, aiming to interrupt further damage. Rajtar and his collaborators found enough HRD to suggest that there is a high probability that Winona County has one or more infection centers. Now, he and his team are trapping spores in Itasca State Park to confirm or correct the record of suspected Heterobasidion that researchers reported there in the 1970s. 

During his PhD, Rajtar also started investigating better ways to detect Phytophthora species, a harmful water mold that can damage plants and forests. Rajtar and his collaborators check trees, plants, and soil in nurseries across the state for the mold, since some nurseries have plant material shipped in from other states. 

researcher takes cuttings from a sick rhododendron
Rajtar samples for Phytophthora from nursery plants. Credit: Robert Blanchette

So far, Rajtar has found 14 previously undetected species of Phytophthora in nurseries and forests in Minnesota. "We have pathogenicity tests set up in the greenhouse now to look at some of these Phytophthora that we've identified as previously undetected in Minnesota and what they can do to some of the host species," he says.

Rajtar and his team are now looking to apply their approach to other priority plant pathogens on MITPPC’s list.

Partnerships build better research

Collaboration is central to Rajtar’s process. He is spending his postdoc working to advance methods for the biosurveillance of invasive pathogens in woody plants, and working with another MITPPC-funded team led by Vinicius Marcilio-Silva, PhD, focused on remote sensing for oak wilt—a fungal disease affecting oak species in Minnesota.

According to Rajtar, Marcilio-Silva’s expertise in this area is helping Rajtar and his team identify and assess HRD infection centers in Wisconsin and Minnesota. Rajtar recently shared coordinates for suspected infection centers in Wisconsin, where MITPPC collaborators plan to sample for HRD and perform spectrometry from there. 

In addition to working with another MITPPC-funded team, the Minnesota Department of Agriculture (MDA) collects and shares soil samples from nurseries around the state when they conduct their routine checks. Over the past 3 years, the MDA has brought Rajtar 40 or so samples to test for Phytophthora. “It allows me to sample way more than I could [on my own] and many different nurseries that I couldn't get to."

Meanwhile, the DNR helps connect Rajtar to land owners with tree stands to test for HRD. "The Minnesota DNR has maps of private landowners with contact numbers,” he says. “They serve as a guide to tell me the stands to look at more closely. I relay the information I find from those stands to them, and then they help me look for other ones.” 
Rajtar points out: “A lot of my work wouldn’t happen without each of these collaborations.”

The “fungi is fun!” guy

Rajtar’s interest in fungi doesn’t stop when he gets home from work, either. "Going out looking for mushrooms on the weekend—there's nothing I’d rather do when it’s nice out," he says. 

three researchers pose with fungi samples in a forest in autumn
From left to right: Nick Rajtar with colleagues Ryan Franke and Colin Peters. Credit: Robert Blanchette

Perhaps that’s why he is so passionate about his job. "I get to go to the field two or three times a week,” he says. “And when I’m out there, I’m obviously doing fieldwork, but I’m also looking for edible fungi. It's just nice to see what's out there."  

Professionally speaking, though, Rajtar has his sights set on an assistant professorship as his next step. Rajtar also says he would consider a postdoc elsewhere in the country. "I'd like to get exposure to different forest systems outside Minnesota, maybe on the West Coast or East Coast, to broaden my expertise in identifying fungi in varied environments," he says.

Whatever happens, he hopes his research helps lay the groundwork for a formal, full-time position in Minnesota focused on biosurveillance throughout the state. “It would be like my [current] position, but more comprehensively sampling around the state.”

Rajtar's publications: 

The Minnesota Invasive Terrestrial Plants and Pests Center research is supported by the Environment and Natural Resources Trust Fund, as recommended by the Legislative-Citizen Commission on Minnesota Resources.

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