The word evokes thoughts of covert military operations, but drones are proving to be a real asset to farmers. Mary Ruth McDonald, a professor in the department of Plant Agriculture at the University of Guelph, recently finished the second year of a three-year study investigating, among other things, how drones could enhance pest-management programs.
Working in 68 fields, just over 280 hectares, in the Holland Marsh agricultural area and wetland north of Toronto, McDonald and her team are discovering that drones can provide a great early warning system for damage to crops from pests, disease and moisture stress.
Usually, crops are assessed by foot soldiers — people walking up and down plots checking leaves for any signs of problems. But that’s by no means an accurate science. “Sometimes what we do when we look at the amount of damage caused by disease is to try to estimate the percentage of damaged plants in the plot — do a severity estimate,” she explains. “And I always find that frustrating, because to me 50 per cent disease often looks like 90 per cent disease, but if you look more closely, you see that not all the leaves are damaged.”
Accuracy down to the last weed
McDonald’s team uses a battery-operated octocopter, an unmanned helicopter with eight rotors and a camera attached to it that can move up and down vertically, from side to side or hover. One person determines the flight path of the drone by plugging GPS coordinates into a computer and an experienced pilot operates the drone.
The drone takes high-definition digital photographs, which are transmitted to a computer and provide a much more accurate assessment — so accurate, in fact, that every weed in a field or plot can be counted. How quickly it works depends on how high the drone is flying. “For some of our fields, it can take 10 or 20 minutes,” says McDonald. “Depending on the purpose of using the drone, it could go higher and get pictures of several fields in 10 minutes.”
The camera provides true-colour images, so any yellowing can be detected, but it also takes near-infrared images, which tells more about how light is reflecting off the leaves of the plant. “In theory, we hope that will show us how the plant is reacting to stress before we actually see the colour change on the leaf with our eyes,” she says. And the farmers enjoy seeing aerial pictures of their land.
Flying a drone takes some practice — the Guelph team is using a company that is experienced in operating them — and windy days are drones’ day off. Even with an experienced pilot drones can crash, and they’ve done so, says McDonald. But they’re made from carbon fibre, so they are easy to repair. “The big concern is the camera,” she adds. “That is expensive, and damage to the lens or the camera would be a bad thing.”
Why earlier is better
According to a drone trade group, Unmanned Vehicle Systems International, agriculture could one day account for the majority of commercial drone use. Indeed, the benefits to farmers of more precise and earlier information about threats to crops are huge. Diseases vary greatly from year to year; downy mildew of onions, for example, shows up some years but not others. But once it does hit a field, it can quickly kill all the plants.
With drones, farmers know immediately if the disease is present and can put a protective fungicide on crops before infection takes hold. “Even one or two days can make a huge difference,” says McDonald.
It also gives farmers definitive information about where in a field pest problems might be brewing. Not only can they target their pesticide application to the affected areas, but other farmers nearby can be alerted to the potential for problems in their own fields.
More specific information also means that farmers can hang back on pesticide use in pest- and disease-free areas of their land. “We’re really interested in — is this the best crop they can get, both in yield and quality?” McDonald says, “and of course, in the most economical and environmentally friendly way.”