A local approach is crucial for the sustainable control of the fall armyworm

“The fall armyworm is spreading worldwide and it is causing significant damage to crops, such as maize, rice, and sorghum”, Van Schaijk explains. “Especially in Africa, fall armyworms pose a growing threat to food security. Farmers use inexpensive chemical pesticides to fight them, but these chemicals are harmful for humans, animals, and the environment.”

Van Schaijk investigated a sustainable alternative: fighting with baculoviruses. These are natural viruses, that specifically infect fall armyworm caterpillars and leave other species unharmed. Farmers can spray the virus over the crop, but that only works when the caterpillars are quite small.

To determine optimal timing, Van Schaijk focused on sex pheromones: scents that female moths release to attract males. By placing traps with the sex pheromones on the crops, farmers can monitor when moth populations are increasing and when new eggs and caterpillars are expected.

No standard solution

Van Schaijk focused on fall armyworm moth populations in Benin and Kenya, and discovered geographic variation in the composition of sex pheromones in female moths. She tested different sex pheromone mixtures as lures in the field and compared them with commercially available lures.

In Benin, the most effective lure was a self-formulated version based on the local population. The lure ensured that the target species was consistently caught and exhibited higher species specificity (catching less non-target moths). Additionally, sex pheromone traps were more effective for determining the optimal spraying time than methods based on the growth stage of maize plants, or just counting eggs on maize leaves.

“These research results make it clear that there is not a one-size-fits all solution for sustainable control of the fall armyworm,” says Van Schaijk. “Local variations in sex pheromones can determine how well attractants work in practice.”

Collaboration and investment

According to Van Schaijk, effectively controlling the fall armyworm requires international collaboration and investment. “Many farms in affected areas lack the resources needed to implement advanced monitoring or biological control on their own. If we want to take global food security seriously, governments, research institutions, and international organizations must work together to make these kinds of methods accessible. That also means investment in subsidies, infrastructure, and local support.”

What is the fall armyworm?

The fall armyworm (Spodoptera frugiperda) is the caterpillar of the fall armyworm moth, a moth native to North and South America. The species has also now spread to Africa, Asia, Australia, and South Africa. The adult moths can travel long distances and lay hundreds of eggs on agricultural crops. The caterpillars  causes the damage on crops. They eat the leaves, stems, and cobs of crops such as maize, rice, and sorghum. A single female can lay up to about 2,000 eggs in her lifetime. In Africa, there are hundreds of millions of people dependent on maize, one of the main crops affected by fall armyworms.

More information

• Renée van Schaijk’s defense will take place on Friday, June 5, at 14.00 p.m., in the Aula.
• You can find the dissertation From pheromone communication to sustainable pest management: Sex pheromone-based control of fall armyworm in Africa on the UvA website.

Text: Institute for Biodiversity and Ecosystem Dynamics (IBED)
Images: Renée van Schaijk (lead photo: Renée during fieldwork in Kenya)