Wasps Can Be Used To Control Crop Pests
What good are wasps? It’s a question asked all the time. And, let’s face it, wasps are routinely demonized. They interrupt picnics (they love beer and fruit as much as we do). Their sting can be painful or cause an allergic reaction requiring medical treatment. And a swarm of them flying at you is genuinely terrifying.
But their reputation as something to be feared is not entirely deserved. In fact, some types of wasps have been shown to be useful in crop pest control. Evidence has been mounting for more than 40 years that wasps—particularly Polistes, which are major predators of caterpillars—may be effective at controlling crop pests.
Beneficial predators
According to Jennifer Jandt, Senior Lecturer in Ecology, University of Otago in New Zealand:
“In a recent study in the Midwestern United States, we moved wasp colonies into a large, screened cage containing broccoli plants. We then added caterpillars and measured how the presence of wasps affected pest consumption of the plants.
The wasps ate all the caterpillars we set out within three hours. They were clever, too, eventually following us as we put the caterpillars on the crops. We also realized some wasps had worked out how to sneak on to our control plants (from which they were meant to be excluded).
We revised our controls and re-ran the study, using a different species of Polistes and a different crop, kale. By day six, all caterpillars from our plants were missing.
The results were clear. We can move Polistes wasp colonies to a new location, and these paper wasps are active predators of crop pests. Pest damage increased when wasps were excluded from the broccoli or kale that caterpillars had been added to. When wasps were allowed to hunt, the crops prospered.
Like Vespula wasps, Polistes can sting if their nest is disturbed. But unlike Vespula, Polistes build small nests under the eaves of buildings. Their nests are relatively easy to remove and relocate to a better spot.
By relocating Polistes wasps into these boxes, we can move nests into small areas or distribute around a crop field. The boxes also act as a buffer to reduce the chances of disturbing the nest and being stung. Polistes wasps seek and destroy caterpillar pests on broccoli plants.”
Pest control potential
If you watch wasps long enough, you can observe them carrying pests away from your home garden, local park, or farm.
So, could Polistes be harnessed as a pest controller? Research suggests they hold biocontrol potential for garden pests. Beyond pest control, wasps are effective flower pollinators and help spread yeasts on grapes that improve wine quality. Wasp venoms are now being harnessed as medicines, including as a possible cancer treatment.
Overall, an argument can be made that wasps should not be uniformly demonized. They exhibit complex social behaviors to rival anything on Game of Thrones. They were the original paper manufacturers, turning dry wood, cardboard, or paper into pulp with their saliva to create the nest cells where their larvae would grow.
Perhaps one day, we can harness them as biocontrol agents targeting crop pests and reduce reliance on pesticides that can negatively affect beneficial insects such as bees. It would be nice to think that their ability to help control pests on valuable crops might one day rehabilitate their reputation. When we provide Polistes wasps in the lab with different-colored paper every day, they produce a rainbow nest.
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