SWFREC scientists have been busy studying new diseases

01/01/2012 01:00:00 AM
By Pamela Roberts

Editor's note: This is the Immokalee Report, a monthly column written by researchers at the University of Florida's Southwest Florida Research and Education Center in Immokalee. This column appeared in the Jan. 15, 2012, issue of Citrus + Vegetable Magazine.

It’s been many years since our center had a monthly column in Citrus + Vegetable Magazine. I needed to decide upon a topic for my first contribution to this renewed column. After almost a week, I still couldn’t decide upon a single topic.

There just has been so much happening in the past few years to try to summarize in a few paragraphs.

Instead, here are some highlights of a few research activities in vegetables and citrus that the pathology group at the Southwest Florida Research and Education Center and collaborators at the University of Florida and U.S. Department of Agriculture have been engaged in:

• Then-doctoral candidate Cheng HuaHaung worked on the current population structure of the fungus that causes Fusarium crown and root rot on tomato and found that silicon suppresses the severity of the disease. The next step would be trials to determine if applications of silicon are useful in the field.

• For several years, our lab has been examining many products, including the role of the fungicide, Tanos, in suppressing bacterial Xanthomonas species that are susceptible or resistance to copper and using this product in programs to manage the disease in the field.

• Our lab received funding to correlate weather events to outbreaks of late blight (Phytophthora infestans), survey fields and characterize the pathogen, fungicide control evaluations, and to participate in Extension on late blight on a nationwide project.

Several fungicides and fungicide programs gave outstanding control of late blight while the new genotypes have been compared to a national and international collection of the pathogen.

• In 2010, watermelon fruit covered in powdery mildew were found in the Immokalee region. This was significant because powdery mildew on watermelon is not very typical in our climate and because of the lack of symptoms on the leaves.

A team of researchers from USDA (South Carolina and Fort Pierce) and SWFREC determined that the outbreak was caused by Podosphaera xanthii, melon race 1, and may be an emerging disease problem. In fact, watermelon fruit covered with powdery mildew were found again this fall.

• In citrus, the Huanglongbing Diagnostic Laboratory is in its fourth year of service to citrus growers providing detection of the bacterium, Candidatus Liberibacter asiaticus, by using real-time PCR diagnostics.

• Field trials evaluating biological control agents, systemic acquired resistance (SAR) inducers, antibiotics and many other products on citrus canker caused by the bacterial pathogen, Xanthomonas citri subsp. citri, were just completed for the fourth season.

• We’re cooperatively working on several aspects of citrus black spot, an exotic fungus (Guinardia citricarpa), causing black spots and fruit drop on citrus. It was first found in the Immokalee region in 2010.

Dr. Pamela Roberts is a plant pathologist based at the Southwest Florida Research and Education Center in Immokalee. She can be reached at pdr@ufl.edu.

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