Using drones and predatory bugs, UC Davis researchers treat crop pests

Entomologists and engineers are collaborating on a new method of controlling agricultural pests. In Santa Monica, Calif., researchers flew drones with light-sensitive cameras over a strawberry field to locate pest-damaged plants. Armed with a map of leaf reflectance patterns, they deployed drones loaded with predatory bugs to spot treat the field. 

 

“Our goal is to eliminate the pests,” said Zhaodan Kong, a UC Davis professor of mechanical and aerospace engineering, whose research includes agricultural and environmental applications of drones. “We use sensors to detect the problem, and then do something to achieve the goal.” 

 

To find insect outbreaks, a drone equipped with a hyperspectral camera flies over the field and senses light reflected from the plants. 

 

“If plants are healthy, they absorb a lot of sunlight for photosynthesis, but if they are less healthy from insect or drought stress, they reflect light in a different pattern,” said Elvira de Lange, a postdoctoral researcher in the department of entomology and nematology. “We can look at these differences and determine which plants need a little bit of extra care.”

 

Light reflectance data from the sensing drone informs the second part of the process. Another drone then delivers predatory mites directly to the infested plants. The mites are natural predators of agricultural pests and are an eco-friendly alternative to spraying pesticide. 

 

Although using predatory mites is an effective biocontrol method, they are much more expensive than pesticide per acre, “but we could potentially make it more attractive to use predators versus pesticides,” according to de Lange. To make the mites economically feasible for farmers, the bugs have to be deployed in small amounts with precision. This need for accuracy presents a new challenge researchers have to take into consideration: wind.

 

In perfect weather conditions, drones can deliver mites without a hitch. On a windy day, the programming becomes more complicated. These drones use a method called time series prediction to calculate the ideal location and time to release the pest control.

 

“The way that it works is like the stock market,” Kong said. “You use the wind direction and wind speed from the past few minutes to predict the wind for the next few seconds.” 

 

In theory, the programming works like a charm, but real-world variables — mainly weather conditions — leave room for improvement. Still, drones are poised to become a valuable tool for farmers to supplement current pest control practices and monitor crop health. 

 

“There are farmers in this area that are using drones regularly,” said Susan Ustin, a distinguished professor emeritus of environmental and resource sciences. “They have knowledge of how they’re managing the field and what to expect. When they have these patterns they don’t understand, they’re close enough to go check it out. It gives the farmers a lot more control over their own land.”

 

Even without mite-dropping capabilities, drones can revolutionize how farmers interact with their fields. Sensing drones are able to survey a large area in a short time, which could save hours of labor in the field. Using light-sensitive cameras can also detect pest activity early to prevent further crop damage. 

 

“With the sensor, you don’t have to wait until you can see the damage by eye,” de Lange said. “There are already very subtle differences occurring in how plants reflect light when they get attacked. We can find the problem and treat a smaller area with pesticide instead of the entire field.”

 

As the technology improves, drones are becoming more of a staple in the agricultural arsenal. Their designs are trending toward larger machines that can fly for longer durations, making them well-suited to regular use for monitoring crop health.

 

“This is 21st century agriculture,” Kong said. “We are trying to be more precise and intelligent instead of using inefficient and labor-intensive practices.”