Spodoptera frugiperda loses sensitivity to insecticide in Argentina.

population of Spodoptera frugiperda in northern Santa Fe, Argentina, he lost sensitivity to chlorantraniliprole ., an insecticide used to control pests in corn and soybeans. The result emerged from a study by researchers at the National Institute of Agricultural Technology (Inta). Researchers warn about the management of the species in a scenario of high selection pressure.

The study evaluated the toxicological response of a population of Spodoptera frugiperda A survivor of the Vip3Aa20 technology. The insects originated from Reconquista, in Santa Fe, in September 2025. The study compared this population with materials from Marcos Juárez, in Córdoba, and from La Cocha, in Tucumán.

Reduced sensitivity

The results showed a strong reduction in sensitivity. The average lethal concentration in the Reconquista population was 21 times higher than that recorded in Marcos Juárez and 9 times higher than that observed in La Cocha. At the doses evaluated, the populations of Córdoba and Tucumán reached 100% mortality. The Reconquista population reached a maximum of 83%, even at 80 ppm.

This finding gains weight after the loss of effectiveness observed in the last cycles of the Bt Vip3Aa20 protein, incorporated into corn in 2011 for the control of Spodoptera frugiperdaAccording to the materials, higher-than-expected damage in some regions increased the reliance on chemical control. In this context, chlorantraniliprole gained prominence due to its action on lepidopteran pests and its widespread use in soybeans, which increased selection pressure throughout the year.

The moment requires adjustment.

The study indicates that the current situation calls for immediate adjustments in pest management. Recommendations include shortening monitoring intervals, especially during warmer periods, and implementing interventions only when population dynamics justify application. Chemical control tends to be more effective when small larvae, between L1 and L2, predominate, exposed on the leaf blade, with 10% to 20% of plants showing grade 3 damage on the Davis scale.

Researchers also highlight the need to improve application technology. Droplet size, coverage, spray stability, and drift reduction all influence the outcome. Control differences can range from 95% to 20%, depending on the management adopted. Another key guideline involves rotating modes of action. The recommendation is to avoid repeat applications within approximately 30-day windows and to discard consecutive applications of active ingredients with the same site of action.