Identifying the adult form of insect pests in a field doesn’t necessarily indicate a need to spray, says insect expert
In a field somewhere on the Prairies, there could be dozens of insect species in the crop. Some of those species could be beneficial and others could be pests that gnaw on the crop tissue or lay eggs on the leaves.
The question for the farmer is how to eliminate the pests and preserve the insects that do no harm.
In January, Danish scientists said optical sensors can be used to distinguish between useful insects and pests.
In a paper published in Scientific Reports, the researchers detail how they used an optical remote sensor to record about 10,000 flying insects in a crop of oilseed rape. The sensor, combined with computer software, correctly identified different species more than 80 percent of the time.
“We demonstrate that it is possible to classify insects in flight, making it possible to optimize the application of insecticides in space and time,” they wrote.
“This will enable a technological leap in precision agriculture, where … prudent and environmentally sensitive use of pesticides is a top priority.”
Their finding could be useful for farmers, who constantly make decisions about insecticide spraying for pests during the growing season. The presence of a flying insect doesn’t always mean it is feeding on a crop.
One example is diamondback moths, pests that feed on green canola leaves. However, it’s the moth larvae, not the flying insects, that eat canola tissue.
“People will run a sweep net through the crop and say ‘whoa, there’s a lot of diamondbacks in my net and want to treat the crop’,” said John Gavloski, extension entomologist with Manitoba Agriculture. “But when they start checking the plants … they realize that the plant (doesn’t) have a lot of larvae.”
That’s why farmers need to scout their fields.
If a high number of diamondback moths are found in a regional trap, it’s not a signal to spray. That count is a signal to check canola crops for larvae and make a spraying decision based on the number of larvae per plant.
On its website, the Canola Council of Canada shares the same message about diamondback moths. The presence of flying moths does not determine crop damage.
“It is the larval feeding that will lead to yield losses, and environmental conditions will ultimately determine how many eggs are laid and whether the larvae emerge and survive, leading to economical feeding damage.”
There may be limitations with sensors that detect flying insects but many public and private scientists are studying automated methods to identify crop pests so farmers can make precise spraying decisions.
Some of the research focuses on pest identification. Other researchers are studying ways to monitor pest damage to the crop.
Trapview is one such company. It has developed a high-tech insect trap that records the number of pests founds in the trap and sends that information, electronically, to a farmer’s phone or computer.
“All information, from all locations is neatly presented in your favourite device to bring your decision-making process to completely new level: raising profits, shortening times, eliminating risks, lowering costs and limiting use of chemicals,” Trapview says.
On its website, the company says its technology is used by apple growers in Poland, lentil producers in Australia and soybean growers in Brazil.
“Trapview solutions are present in more than 40 countries around the world… monitoring more than 50 insect species.”
Adama Canada, which has its head office in Winnipeg, is testing the Trapview technology at several locations on the Prairies.
It might help farmers make better decisions about insecticides, but Gavloski wonders about the economics. Sensors, traps and other technology to collect data on pests might make more sense for a farmer who grows peaches, apples or potatoes.
It may not be economical, or make sense, for broad acreage crops like canola or wheat.
“In some horticulture crops they actually make decisions, management decisions, based on their trap counts. We don’t do that in field crops,” he said.
Manitoba Agriculture operates a network of traps that monitor insects including diamondback moths. But, again, the counts from those traps shouldn’t be used to make a ‘spray or don’t spray’ decision.
“Diamondback moths, bertha army worms. The (count) numbers we get are strictly to tell (growers) to scout for the damaging stage – the larvae,” he said.
“They’re a tool, telling you to prioritize your scouting. But they don’t mean that field needs to be sprayed.”