Study shows wasps are effective in controlling pests

Common wasp species can be valuable in sustainable pest management. These insects can combat the borer Diatraea saccharalis, common in sugarcane plantations, and also the caterpillar Spodoptera frugiperda, which mainly attacks corn plantations, two crops with high commercial value. Controlled experiment results showed that wasps effectively reduced pest populations, and plants even suffered less damage when they were present. 

The study that revealed the effectiveness of wasps as predators of these pests was carried out by researchers from University College London (UCL), United Kingdom, the Faculty of Philosophy, Sciences and Letters of Ribeirão Preto (FFCLRP) of USP and Unesp, Jaboticabal campus . At Unesp, it was professor Odair Aparecido Fernandes, from the Faculty of Agricultural and Veterinary Sciences (FCAV), who participated in the research.

The researchers point out that wasps are found all over the world and can easily be used on a small or large scale to control a number of common pests. “There is a global need for more sustainable methods to control agricultural pests, reduce excessive dependence on pesticides or imported pest controllers. Wasps are very common but little studied; With this research we provide important evidence of their economic value as pest controllers”, says the study's lead author, Robin Southon, from UCL.

The experiment was the first of its kind carried out under controlled conditions and outdoors. Corn infested by the caterpillar Spodoptera frugiperda, also known as army worm, and sugar cane by the sugarcane borer Diatraea saccharalis, was used. The efficiency of some species of wasps in crops and in the diet of caterpillars had already been demonstrated, say the researchers, “but without the detailed control carried out in this research, with controlled infestation inside and outside the plant”. 

The experimental part of the study was carried out in Ribeirão Preto, says FFCLRP professor and study co-author Fábio Nascimento, and carried out in a greenhouse, with the insertion of pots with the plants; first, from sugar cane and then from corn, already randomly infested with the pest larvae, and in two other ways: externally and internally in the plant. In the greenhouse were nests with common wasps, called Polistes satan. “The wasps showed efficiency above what we expected in both crops – 90% and 100% on caterpillars exposed on leaves, and 40% and 60% on caterpillars sheltered inside sugarcane and corn.” 

The Brazilian researcher celebrates the results: “Contrary to what was thought, they are able to find the caterpillars between the junctions of the plant leaves; thus, their efficiency as controllers is significant.” 

Wasps can integrate pest management

The group intends to continue the work with larger trials and active agricultural activities. But researchers already argue that wasps should be considered pest controllers and that they should form an important part of an integrated management scheme. 

Scientists believe in the effectiveness of a multifaceted approach to combating pests. “We’re not saying that farmers need to stop what they’re doing and start using wasps in their current pest management strategies; instead, we are adding a new element to the pest control toolkit,” they emphasize. “Social wasps, like the ones we studied, are generalist hunters, therefore complementary to existing approaches. These insects could reduce the likelihood of a pest developing resistance to a specific pesticide or biocontrol agent,” says Southon.

According to Professor Nascimento, the use of wasps from native species that are already part of the local ecosystem tends to be more sustainable as it also preserves the biodiversity of that area. “Our study provides evidence that wasps could be a cheap and accessible form of pest control, particularly useful for small-scale or subsistence farmers in countries like Brazil, who could attract and encourage wasps to establish themselves.”

Seirian Sumner, from the UCL Center for Biodiversity and the Environment, points out that when using chemicals to kill pests, farmers often also kill the same insects that can provide natural forms of pest control. And this happens with social wasps. “We have to make the most of what we already have around us.” 

Sumner hopes the research highlights the value of wasps. He has already led a previous study on these insects, showing that many people don't like them because they don't understand their role in the ecosystem. “It’s not just about agriculture, it’s about wasps in general and their role in regulating other insect populations,” says Sumner.

In the second stage of the study, says the professor at USP in Ribeirão Preto, the wasps will be tested in an open cultivation area. Nascimento and professor Odair Fernandes, from Unesp, supervise a postgraduate student who will test the effectiveness of wasps in organic farming areas in Jaboticabal.

“Wasps are in decline around the world, similar to bees, which are more beloved; losing these insects, the result would be an increase in aphids, flies and other nuisances”, warn the researchers. They claim that yards and gardens can also benefit from a more wasp-friendly attitude. “Instead of killing wasps and using pesticides on your plants, treat your local wasps like the pest controllers they are.”

The study received support from Fapesp and the UK Department for Business, Energy and Industrial Strategy.