When you pick up a carton of fresh blueberries or strawberries, the last thing you want to think about is an insect infestation. Yet, a tiny invasive pest, Drosophila suzukii, poses a massive threat to these crops. This fly is responsible for an estimated $500 million in crop losses annually in the U.S. alone. While pesticides have been the primary defense, concerns over chemical residues and growing insect resistance have created an urgent need for new solutions. Based in the Wong Lab at the UF Department of Entomology, researcher Zhangrong Song is tackling this problem from a unique angle: decoding the invisible language of microbes.
“To describe it simply, my research is to find the microbial-based volatiles which can repel or attract Drosophila suzukii, so we can control it in the field,” Song explains. The goal is to develop an alternative, environmentally friendly method of pest management that doesn’t rely on heavy pesticide use. What makes Drosophila suzukii, also known as the spotted-wing drosophila (SWD), such a formidable pest is its unique biology. Unlike the common fruit flies that are drawn to overripe or rotting fruit, the female SWD has a formidable tool. “The females of this fly possess a serrated ovipositor, which can let them lay eggs inside of the intact fruits,” says Song. This means that by the time a berry is perfectly ripe and ready for harvest, it may already be infested with developing larvae, making a “zero tolerance” policy for this pest a necessity for growers.
Song’s research began with a simple but crucial observation. When SWD forages on a fruit, it transmits microbes from its own body onto the fruit’s surface. The team hypothesized that these microbes then begin to alter the fruit’s chemical “scent,” or volatile profile, sending a signal to other flies in the area.
To test this, they designed a behavioral experiment. “We found that flies will be attracted to the foraged fruits in a very short time window,” Song notes. The fruit that had been visited by a fly within the last 24 hours was highly attractive to other flies. However, after 48 hours, that same fruit lost its appeal. This suggested that a specific microbial community, thriving at the 24-hour mark, was producing a distinct beckoning aroma, or signal.
Using advanced techniques, the team profiled both the microbes and the volatile chemicals present on the fruit at different time points. They identified specific bacteria, such as Acetobacter and Corynebacterium, that flourished after being deposited by the flies. These bacteria, in turn, produced a unique cocktail of volatile chemicals. “We generate a list of specific chemicals,” Song says, “and luckily we found some specific chemicals which can enhance the attractiveness of the strawberries to the flies.”
This discovery has immediate, real-world applications. “We try to combine these chemicals with some commercial monitoring systems already in place… We found that combined with our chemical, it can enhance the capture rate and the early detection of the SWD,” Song reports. Better traps mean farmers can monitor SWD populations more accurately and know precisely when, and if, they need to intervene, potentially reducing overall pesticide use.
The research has also uncovered the other side of the coin: repellents. From their list of candidate chemicals, the team identified some that have a strong repellent effect on SWD in the lab. While more research is needed to validate their safety for use on crops, “we think it has a high potential to be alternative methods to control the Drosophila suzukii.”
This work reframes our understanding of the relationship between insects and the plants they feed on. It’s not a simple two-way street but a complex, three-way conversation between the fruit, the insect, and the microbes they carry. Microbes not only act as a signaling system but can also help the fly’s offspring by breaking down the fruit and making nutrients more readily available.
The next steps are focused on refining these tools for field use. For the attractant, the goal is to develop encapsulation methods that allow the chemical to be released over a longer period, making the traps more convenient for farmers. For the repellent, the focus is on rigorous safety validation and determining the most effective dose.
While complete eradication of this pest is a distant, long-term goal, Song’s research provides a powerful new set of tools for management. By listening in on the chemical conversation between microbe and insect, we may be able to turn their own language against them, protecting our food in a smarter, more sustainable way.