Wasps as allies in agricultural pest control

Common species of wasps may be valuable in the sustainable management of agricultural pests, including the sugarcane borer (Diatraea saccharalis) and the caterpillar Spodoptera frugiperda, which mainly attacks corn plantations.

Results from a controlled experiment showed that the presence of wasps in crops effectively reduces populations of these two pest species and also reduces damage to plants. The study was carried out by researchers from University College London (United Kingdom), the Faculty of Philosophy, Sciences and Letters of Ribeirão Preto at the University of São Paulo (FFCLRP-USP) and the Universidade Estadual Paulista (Unesp) in Jaboticabal. The data was published in the magazine Proceedings of The Royal Society B.

The research received support from FAPESP and the UK Department for Business, Energy and Industrial Strategy, under the Foundation's agreement with the British Council and Newton Fund.

The authors point out that wasps are found all over the world and can be easily 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 and reduce excessive dependence on pesticides. Wasps are very common, but little studied. With this research, we provide important evidence of their economic value as pest controllers,” said study lead author Robin Southon from University College London.

The experiment was the first of its kind carried out under controlled conditions and outdoors. Maize infested with the Spodoptera frugiperda, popularly known as army worm, and sugar cane containing Diatraea saccharalis. The efficiency of some species of wasps in crops and in the diet of caterpillars had already been demonstrated, the researchers explained, “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 the professor at FFCLRP-USP 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,” said Nascimento.

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. Therefore, their efficiency as controllers is significant.”

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, in 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; rather, we are adding a new element to the toolkit,” they said. “Social wasps, like the ones we studied, are generalist hunters and complement 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 native wasps, which are already part of the local ecosystem, tends to be more sustainable by preserving 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 Center for Biodiversity and the Environment at University College London, states that, by using chemical pesticides, farmers can also kill insects that act as natural pest control. “We have to make the most of what we already have around us.”

Sumner hopes the research highlights the value of wasps. “It's not just about agriculture, it's about wasps in general and their role in regulating other insect populations,” Sumner said.

In the second stage of the study, the wasps will be tested in an open cultivation area. Nascimento and the teacher Odair Aparecido Fernandes, from the Faculty of Agricultural and Veterinary Sciences (FCAV) at Unesp, are guiding a postgraduate student who will test the effectiveness of wasps in organic farming areas in Jaboticabal.

“Wasps are in decline around the world, as are bees, which are more beloved. The result of the loss of these insects 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.

*With information from Journal of USP and the Communications Office at University College London.