Inside a lab in Redland, behind double doors that require a lab coat to enter, a team of scientists is breeding a tiny terror.
The invasive pests, known as short-spined thrips, may be microscopic, but they’re a menacing threat. South Florida’s warming climate offers an ideal place for them to thrive — putting local nurseries at risk.
“Over time, we realized this is a very difficult pest to control,” Alexandra Revynthi, an assistant professor at the UF/IFAS Tropical Research and Education Center in Homestead, said. “It’s extremely aggressive. Within just a few days, it can cause serious economic damage.”
When the invasive pests first appeared in South Florida a few years ago, the timing couldn’t have been worse. It was spring, when delicate ornamental plants like gardenias, hibiscus and mandevillas were in full bloom and preparing to be shipped. The state imposed a quarantine to prevent the further spread.
There are millions of dollars worth of plants in every nursery, and there are hundreds of nurseries in Miami-Dade County, said Barney Rutzke, an owner of Railroad Nurseries, a 300-acre farm in Homestead. He predicted that the pests could have eaten away at 30 percent of their expected profits when they first arrived in 2023.
“The state or the USDA needs a Rapid Response Fund for invasive pests,” said Rutzke. “Instead of just shutting us down, saying you can’t ship plants. It hits us economically and leads to unnecessary spraying.”
Rutzke helped bring farmers together to pool money and jump-start this research on the thrip a few years ago because they needed new solutions.
In desperate situations, the nurseries spray chemical insecticides twice a week. Not only is frequent spraying bad for the applicator’s health and the environment, but Revynthi and her team found that they aren’t as effective as they should be and could eventually breed “insects that survive chemistry, super pests that cannot die.”
Now, the lab has a lot more answers. They still have a lot to learn, but are a step closer to finding out how to put a stop to them. And they’re approaching it with multiple methods of attack.
‘When you understand the enemy, you can fight it’
Just how the short-spined thrip made it into South Florida is still up for debate.
Were they stowaways on one of the vast containers that stop at Port Miami? Did they sneak in with tourists or through unregulated trade channels?
Before researchers could figure out how to manage the pest, they had to identify exactly which species of thrips they were dealing with. There are thousands — and every microscopic hair on the insect mattered in identifying it.
Once they did, they turned to scientific literature from Asia, where the pest originated. Over and over, the thrips was described as an “extraordinary pest,” one unlike anything researchers had seen before. Still, many questions remained: how it behaved throughout the year, how it reproduced and how it responded to temperature changes.
“When you understand the enemy, you can fight it,” Revynthi said.
That understanding came from hours of close observation. Isamar Reyes Arauz, a research assistant in the lab, watched the insects around the clock. Using a microscope connected to a computer screen, she could observe them moving at 100 times magnification.
Arauz tracked every stage of the thrips’ life cycle — how they moved, what agitated them, how they reproduced and when they died. She applied to the Entomological Society of America to name the insect the short-spined thrip.
The short-spined thrips move from ornamentals like gardenias to vegetables like peppers. They feed by piercing plant tissue and sucking out the cell contents, draining leaves of life and leaving behind silvery scars. They poop as much as they eat – leaving behind a trail of little black dots.
But scientists learned thrips don’t do well without their food source. So one piece of advice to growers was between production cycles to clean the nursery and leave it without water for as long as their schedule permits before bringing new plants in.
A perfect climate
South Florida’s tropical and subtropical climate makes it a hotspot for invasive insects.
“South Florida is like a Petri dish when it comes to invasive pest species,” Revynthi said.
Researchers closely studied how thrips respond to temperature, simulating cold and heat exposures to see how long the insects could survive.
What they found wasn’t encouraging. The thrips’ preferred temperature – about 80.6 degrees Fahrenheit – matches South Florida’s average almost perfectly. Their desired humidity, 70%, is also the regional average.
And summer heat doesn’t kill them.
Production may dip slightly in winter, but South Florida’s short stretches of sweatshirt weather aren’t enough to knock populations back significantly. As areas become warmer as greenhouse gases heat the planet, more areas of the state and elsewhere will have favorable conditions for invasive pests.
“So pretty much, thrips have no reason to complain,” Revynthi said. “They just feed, reproduce and keep growing.”
Biological warfare
One line of defense against the thrip that researchers found is biological control. Paola Villamarin’s job is to find insects that naturally prey on thrips. Similar to releasing ladybugs to control aphids or spider mites.
The goal is to target thrips at every stage of their life cycle. One option is a small, worm-like organism that attacks them in the soil. Another contender is a tiny red mite that looks like a spider, moving quickly, earning it the nickname “crazee mite,” Villamarin said.
Tests are set to begin on how five different beneficial insects perform against thrips on gardenias.
Studying insects also means being plant doctors. Researchers tend bean and pepper plants daily to keep healthy insect populations growing. Beans, Revynthi said, are like French fries to thrips. Other plants, like marigolds, are grown to see if they can lure the insects away from more valuable crops.
The team has also identified a simple dip treatment that can be used during plant propagation to discourage thrips. They’re working with the USDA on traps as well, testing which colors might attract the pests.
Their findings, published in the Journal of Economic Entomology, are the most detailed portrait yet on the pests. Though the solutions to mitigating the damage caused by thrips seem small individually, the hope is that in aggregate all the steps add up to helping growers keep plants market-ready.
Ashley Miznazi is a climate change reporter for the Miami Herald funded by the Lynn and Louis Wolfson II Family Foundation and MSC Cruises in partnership with Journalism Funding Partners.
This story was originally published by the Miami Herald and shared in partnership with the Florida Climate Reporting Network, a multi-newsroom initiative founded by the Miami Herald, the Sun-Sentinel, The Palm Beach Post, the Orlando Sentinel, WLRN Public Media and the Tampa Bay Times.
