Researchers at the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) Indian River Research and Education Center’s (IRREC) Entomopathogenic Fungi Research Laboratory are investigating fungal endophytes and their potential use as alternatives to chemical pesticides.

Terri Price-Baker, a biological scientist in the Entomopathogenic Fungi Research Lab at IRREC, has been working with Biological Scientist Pasco Avery for the last few years on testing the efficacy of fungal-based biopesticides.

“Fungi is really unique and interesting. Fungi have already proven to be a powerful symbiote in nature,” Price-Baker said. “About 95% of the world’s plant life exists because of symbiotic mycelium that stretches all over the world. It is fascinating to me using fungus as a control for pests and pathogens.”

Fungal endophytes are symbiotic fungi that reside within plant tissues. They provide many benefits to plants including nutrient absorption and disease resistance. They make their way into a plant system and can become a whole new organism that is a symbiote of the plant.

She said once inside the plant host, they cause no harm or disease and through excreted secondary defense chemicals, they provide defense for the host against pests and pathogens alike.

They have been researching fungal endophytes for the past five years. Price-Baker joined Avery three years ago.

“Dr. Avery has been really passionate about this because we’ve had really good effects with fungal biopesticides. We’ve even been able to infect the Asian citrus psyllid, which is a huge problem for citrus currently,” she said.

Their ultimate goal is to find out which genes are responsible for the various secondary defense chemicals and whether they can ramp up the efficacy of those genes using biotechnology and other technological advancements.

Those discoveries would allow them to create targeted treatment plans for different crops, pests and pathogens.

Citrus has been the primary crop they have worked on for their research. Price-Baker said they would like to expand the use of fungal endophytes into other staple crops including tomatoes, sugar cane and potatoes, which Florida is one of the United States’ largest producers of, along with corn and wheat.

“We would like to target those specific crops as well as the pathogens that they are dealing with,” she continued.

Some of the more surprising results they have discovered so far have been with Beauveria bassiana, an entomopathogenic fungus widely used in biological pest control. They tested it on citrus and after doing a single foliar spray, found it in every tissue of the plant.

She said it was able to migrate into the stems, roots, and the new flush, which hadn’t been treated previously.

“The endophyte is capable of moving into other parts of the plant, which was amazing to us and we also found new modes of entry. Usually, the way that it works is the spore will come in contact with the surface of the leaf. It’ll release digestive enzymes through an appressorium, and it’ll enter the plant system that way.”

They also witnessed spores entering through open stomata of the leaf’s surface, which was not a previously known mode of entry.

Price-Baker and Avery were able to discover a timeline for the endophytes. They found that they last about four and a half months before retreatment needs to occur again, which she said is good news for growers because it’s more cost effective than synthetic pesticides.

Even with everything they have discovered so far, there are many questions that still remain. Their focus for this year will be on whether it can destroy the bacterial pathogen responsible for citrus greening and produce a deterrence effect they can see in their field work.

“We will be monitoring pest pressure and keeping out for natural predators and beneficials in the field too. We will also be monitoring growth effects and environmental and soil conditions,” she said. “There’s a lot of questions that remain unanswered. This is really our proof-of-concept experiment. So it’s proving that it can do what we think it can do.”

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