As faculty at a land grant institution, I’m asked from time to time to put together information that justifies tax dollars used for our various research, teaching, and extension endeavors. Recently, I went through this exercise for the UF/IFAS diagnostic services provided to the clientele I serve. I quickly realized that we’ve seen a lot of change over the past couple decades with several new diseases emerging along the way. In each case, unknown problems represented huge challenges. A diagnosis is hardest to produce the first time you have to do it. After ruling out the common and known, the unknown that’s left is quite big. I’ve relied on our UF diagnostic clinic to help, and couldn’t have done it without them.

The Plant Disease Clinic at UF started back in the 1950s when Dr. Mullins first started accepting samples. A handful of faculty have helmed the lab over the last ~75 years. Dr. Tom Kucharek was director of the clinic in the 1970s and was on the committee that hired me in 2003. He has written a history of the service, the buildings that the lab has occupied on campus up through his retirement in 2004, and some personal details of the scientists involved. My close colleague Dr. Carrie Harmon has directed the clinic since 2009 and oversaw the construction of the current Plant Diagnostic Center (PDC) building we occupy today that is located behind Fifield Hall on the Gainesville campus. It’s no longer just a clinic, but serves research and teaching functions as well. Students and diagnosticians trained in that lab now run their own labs at the University of Maine, University of Connecticut, University of Missouri, Purdue University, and private industry.

Funding has come primarily from grants, but also from fees paid by our clientele. The longest running grant award established the National Plant Diagnostic Network (NPDN), which has provided essential equipment, staffing, and training opportunities over the last 22 years. The UF lab in Gainesville is one of five NPDN regional centers in the country tasked with providing diagnostic services to protect the US food supply and agricultural production. The program has most recently been funded through the Food and Ag Defense Initiative under the National Institute of Food and Ag within the USDA.

So what has the PDC done for Florida blueberries? 

New Disease Discovery

If we look at my time here at UF, samples submitted to the PDC have been instrumental in identifying new threats to our industry. This first step has then allowed me to develop short, medium, and long-term management options through collaboration and research, but the first step involves knowing what the problems are. One of the first new diseases I encountered was algal stem blotch caused by Cephaleuros virescens in 2005. The pathogen was known to cause disease in tropical crops and brambles, but seeing it on southern highbush blueberry was a surprise. A similar story unfolded when we found bacterial leaf scorch caused by the Xylella fastidiosa on Florida blueberries in 2009. The clinic quickly established a diagnostic protocol to distinguish it from drought and salt stress using an ELISA protocol developed for woody ornamentals. It was found not to be a reliable method, and through NPDN funding, we purchased equipment needed to offer a more reliable and selective PCR technique for blueberry quickly thereafter. In 2009, we also found new fungi causing severe stem blight disease because the diagnosticians in the clinic noted the spores produced didn’t look like the reported Botryosphaeria dothidea. Blueberry red ringspot and Blueberry necrotic ringblotch viruses were confirmed on samples with odd leaf symptoms submitted in 2013. Target spot caused by Corynespora cassiicola was another new disease found through samples submitted to UF clinics and described in collaborative efforts with our colleagues. Mysterious runs and patches of dead Arcadia plants in south Florida in 2017 led to the discovery of streaming and bacterial wilt caused by Ralstonia solanacearum for the first time in southern highbush blueberries. Terrible dieback on a promising variety Flicker was attributed to fungicide resistance in the anthracnose pathogen Colletotrichum in 2018. The most recent (as of today anyway) find has been Cercospora leaf spot on the Sentinel variety in 2022. 

Some plant pathologists go their whole career and don’t discover a new disease affecting crops they study; we’ve had our share. I didn’t find all of these by myself, I had many collaborators, and chief among them were diagnosticians within the Plant Diagnostic Center and other UF Plant Disease Clinics. I’ve done some amount of research on all of these over the years, if only to establish that they were not problems to worry too much about. Others, we’ve developed management strategies that we can work with, or recommended different varieties that were not as affected. My work started with knowing what diseases we were facing, what caused it, and what options could we explore.

The Numbers

It’s easy to count samples, categorize the different diagnoses we give out over a given amount of time, and record from where and whom samples were submitted. That knowledge gained is sometimes too late for one field or even season, but may save another from the same fate. Quantifying the amount of disease we prevent or crop we save is difficult to do. How many berries would your operation produce without knowing what any of those diseases are or what your management options were to prevent them? 

Over the past 10 years (2015-2025) we’ve recorded just over 3,000 blueberry samples in all UF labs. This doesn’t count the ones we guess at in the field or over email. Greater than 95% of those 3000 have been processed at the PDC in Gainesville, 5% at one of the other clinics in the state. The vast majority have come from Florida, but 11 other mostly SE states use our service as well. I think the blueberry that traveled the farthest came from Poland, where a grower was concerned she may have had Ralstonia after reading one of our extension publications (it was negative). The pie chart below breaks out some of the diagnoses or types of tests run on some of those 3000 samples. I think it’s important to note the no pathogen found and abiotic disorders categories in the chart. It isn’t always disease, and that’s also a good diagnosis that allows us to focus on other issues without wasting resources that can’t help the problem at hand—also a difficult value to quantify.

In summary, I wanted to write this article to say thanks to the PDC, the diagnosticians I’ve worked with over the years, and our UF administration for supporting the plant diagnostic mission. I hope that I’ve conveyed that I certainly feel the federal grant dollars awarded UF in support of the PDC have had a tremendous positive impact on our industry. Finally, I want to thank all of you for submitting those samples to us, paying those fees to support the process, and for your support.

CREDIT:
PHIL HARMON