Fighting nature with nature: Scientists mobilize biological control against devastating fall armyworm

Source(s): Entomological Society of America

By Sara Hendery

Despite the fall armyworm’s current track record of threatening the food security of millions, there is a safe, economical, and efficient method that could put an end to the invasive pest’s reign, say scientists at Virginia Tech.

Native to the Americas, the fall armyworm’s entry into Africa in 2016, and its more recent entry into Asia this year, has farmers panicked with its resilience to most control methods. However, Muni Muniappan, Ph.D., director of the Feed the Future Innovation Lab for Integrated Pest Management at Virginia Tech, with collaborators in East Africa, has identified two local egg parasitoids that offer a promising solution to the havoc-wreaking fall armyworm (Spodoptera frugiperda).

Like any hungry caterpillar, the fall armyworm feeds, but in its arsenal is also the ability to fly 500 kilometers in its adult lifespan, lay thousands of eggs, and burrow inside plant bodies, rearing pesticides powerless. Repeated application of chemicals to mitigate the spread of the pest could force the fall armyworm to develop resistance, in addition to the growing number of health concerns pesticides cause for human, animal, and environmental life. Muniappan said that genetically modified crops could be a potential solution for the pest, but, like many problems above the surface, some answers take a little digging.

“While the fall armyworm threatens more than 80 plant species, it favors maize, of which there are dozens of varieties that vary from country to country, culture to culture,” Muniappan says. “Creating resistant varieties would be helpful, but time is not something we have on our side, and an immediate solution is necessary.”

Within the coming year, Muniappan expects to initiate a plan for augmentative release of the natural enemies Trichogramma and Telenomus, both parasitoid wasps, into Kenya, Tanzania, and Ethiopia, three countries the United States Agency for International Development (USAID) funds the team to work in. Team collaborators will be mass-rearing and releasing the parasitoids to enhance their effectiveness.

Tadele Tefera, Ph.D., of the International Centre of Insect Physiology and Ecology, along with collaborator Peter Malusi, helped Muniappan identify the parasitoids in Kenya in July.

“Biological control is a viable solution for managing the fall armyworm,” Tefera says, “because it is environmentally friendly, socially acceptable, safe for humans and animals, and self-perpetuating. These two tiny wasps we’ve identified search for and lay their eggs on fall armyworm egg masses. Their value is enormous because they kill fall armyworm eggs before they reach the larval stage, which is when they’re most destructive to crops.”

The biological control of the fall armyworm has a host of benefits:

  1. Location. The parasitoids are naturally found in Africa, so introduction does not pose a threat of turning a non-native species into an invasive species on the continent.
  2. Cost. Mass-rearing the parasitoids on an alternative host like Corcyra cephalonica, as planned, instead of the fall armyworm will cut costs in half. The cost benefit is crucial, as the fall armyworm has the potential to cause billions of dollars of damage in multiple countries, many of them already plagued by poverty.
  3. Natural enemies to many. The two parasitoids will act as natural enemies to most caterpillar pests that harm a wide array of crops, not just maize, further ensuring the goal of global food security.

The Innovation Lab has already had some success monitoring the fall armyworm: In January, the team prepared a risk assessment of fall armyworm for the USAID mission in Egypt that modeled and predicted the pest would move into Yemen due to wind currents from Sudan. Entomologists in the area have now confirmed the prediction to be true.

“A third of the African population depends on maize as a source of food and income, and with the introduction and confirmation of fall armyworm in more than 35 African countries, the continent faces the grandest of challenges,” Tefera says. “This calls for concerted efforts to fight and defeat fall armyworm.”

Along with maize, sorghum, cotton, and more, the fall armyworm creates pinholes in plant leaves, easily making its way on to the next country, the next crop, the next devastated community. For the upcoming year, the Innovation Lab hopes to impede its quick movement, and safely – the team is planning multiple workshops across Africa and Asia to help developing countries manage the unruly pest with Integrated Pest Management technologies and turn its vast army into an army no more.

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