Spraying not the answer in all cases where crop pests are present, says Field Heroes

By Tim Kalinowski


While acquiring good employees is a huge challenge for farmers in Canada today, there is a source of unlimited free labour out there for farmers, says Field Heroes spokesperson and AAFC research scientist Haley Catton, which they are either unaware of or don’t understand the value in. Catton is speaking about beneficial insects already located in crops which help take care of common insect pests.

“The Field Heroes campaign is all about raising awareness in a crop field where there are many different kinds of insects—lots of beneficial insects, some neutral, and a few pest species.

“Historically, producers focus on the pest species because those are the ones costing them money. And so they may, at times, misconstrue beneficial insects as pests. We are raising awareness that beneficial insects provide ecological services for producers, and we also want to let farmers know they bear a hidden cost when they spray pesticide— they are killing the pests but also these beneficial insects. We want them to make more informed choices when they should use insecticides.”

With the cost of pesticide rising and the need for greater frequency of spraying in today’s agriculture, Catton figures if she and her colleague’s research can help save farmers a few bucks while helping grow beneficial insect populations across the Prairies, it might be a win-win for everybody.

“There are four steps to this campaign,” she explains. “The first one is raising awareness so farmers have even heard about beneficial insects. Then the next step is raising interest where the farmer might say, ‘Okay, interesting. But what’s in it for me?’ The third step is understanding, where a producer would know what beneficials are important, and how, and how not to kill them. And then ultimately we are hoping for new behaviours where farmers are considering these beneficials in every step they make.”

Catton gives a few examples to illustrate her point.

“A really good example is cereal leaf beetle, which is a pest on cereals; especially wheat,” she says. “It’s an invasive insect that’s new to Alberta since 2005, and it also has a tiny little wasp that came with it that’s a beneficial insect. The wasp will eat the pest from the inside out, and when we do surveys on this wasp where there are no sprays, we find they are killing half of those cereal leaf beetles on average in any given field. This is a case where the beneficial insect, the biological control, has led us (at AAFC) to recommend you don’t spray— we will send you these beneficial insects instead.”

Aphids are another one which seem to prompt farmer’s spray-just-in-case tendencies, regardless of what’s actually going on in the field, says Catton.

“The beneficials in this case would be lady beetles (lady bugs) and lady beetle larvae, which look little alligators,” she says. “Aphids are a good example because they reproduce so quickly, and the beneficials can act on them so quickly. There are lots of recommendations out there where people are saying in this case, ‘Don’t spray.’

“You will actually see farmers on Twitter right now posting photos of their sweep nets (sampling nets) where they say: ‘A week ago I had all these aphids and some lady beetles, and now I went out and did my sweep today and there are way less aphids and far more beneficials.”

A colleague of Catton’s has developed an app where farmers can use a sweep net and see how many aphids they have versus lady beetles and lady beetle larvae, and punch that data into the app.

“The app will then calculate whether or not it is worth it for the farmer to spray,” she says. The app is called the “Cereal Aphid Manager Mobile App” and can be downloaded from the Agriculture and Agri-Food Canada website, explains Catton, and is a simple tool to help farmers make better spraying decisions. Beneficial insects can also help alleviate more serious pest species problems like bertha armyworms or wheat stem sawfly and cutworms if present in low densities in a crop, Catton goes on to say. Each has particular parasitoids which do feed off of them. Cutworms may be the best and most disgusting example of these parasitoids at work, she says.

“Cutworms are eaten by a lot of different insects,” she says. “They also have parasitoids, beneficial insects which lay their eggs inside the cutworm and eat them from the inside out before bursting out. It’s really gross, but there are some hypotheses that every insect out there has its own parasitoid. It may be gross, but it can be really beneficial in the case of cutworms to a field.”

Catton says she will be the first to acknowledge in a case like bertha armyworms, which can have sudden massive outbreaks, spraying still has to be a major part of a farmer’s toolbox.

“Sometimes you have to spray,” she concedes. “But in that case we talk about economic thresholds: Is there enough pest insects to make it worth it to spray? We don’t want to guilt farmers into not spraying at all— sometimes they need to. But when they are not sure, or its borderline, we want to get away from that thinking where a farmer says: ‘Oh sure, I’ll do it just in case.’”

Catton says in case of beneficial insects, it’s not a resource farmers should throw away lightly.

“Farming is getting more integrated, and farmers have to consider everything on a holistic level,” she says. “The market prices of their crops, the agronomics, pest pressures and weather, and all these things. Field Heroes is along that line that says lets think about the insects in the crop as a whole system. If we do that, we realize the system itself provides levels of pest controls on its own, and we don’t want to waste or destroy that for no reason.”

To learn more about beneficial insects in crops follow Field Heroes on Twitter, or visit the organization’s website at www.fieldheroes.ca.

Photos courtesy AAFC
Mine! No, Mine! Ground beetles fighting over a cutworm. An example of Field Heroes caught in action.