# Validamycin Inhibits the Reproductive Capacity of Spodoptera frugiperda (Lepidoptera: Noctuidae) by Suppressing the Activity of Trehalase

## TL;DR

Validamycin, a natural compound, disrupts the reproduction of fall armyworm by inhibiting a key sugar-processing enzyme, offering a safe and eco-friendly pest control option.

## Contribution

Validamycin is shown to inhibit trehalase activity and reduce reproductive capacity in Spodoptera frugiperda, offering a novel bioinsecticidal strategy.

## Key findings

- Validamycin injection reduced egg production, caused ovarian atrophy, and shortened the lifespan of female moths.
- Validamycin inhibited trehalase activity, leading to reduced glycogen levels and disrupted eclosion in S. frugiperda.
- Egg blackening and clumping in the oviduct were observed at low validamycin doses, impairing reproduction.

## Abstract

The fall armyworm is a highly destructive crop pest that now threatens global food security. Current control relies on chemical sprays and genetically modified crops, but the worm has become resistant to both, so safe, green alternatives are urgently needed. We tested a natural compound called validamycin that blocks the insect’s main energy sugar and upsets its reproduction. Tiny doses injected into pupae greatly reduced the number of eggs laid by female moths, shortened their lives, and caused many eggs to fail to hatch, leading to smaller future populations. Because validamycin comes from a soil microbe and is harmless to humans and wildlife, it could form the basis of a new generation of eco-friendly pesticides that help farmers use fewer chemicals while still protecting harvests and the environment.

Spodoptera frugiperda (J. E. Smith, 1797), an omnivorous crop pest worldwide, reproduces prolifically. Validamycin, a competitive natural inhibitor of trehalase, is regarded as an effective and safe insecticide. Pupae were injected with a validamycin gradient (0.5–10 µg/µL) to block trehalase; enzyme activity and the Vitellogenin gene (Vg)/its receptor gene (VgR) expression (rpL10 reference) were subsequently quantified to determine the compound’s impact on S. frugiperda ontogeny and fecundity. Validamycin directly inhibited pupal membrane-bound trehalase, sharply lowering glycogen. Both pupal and adult mortality rose with dose, yielding marked abnormalities versus the Control Check (CK) group. At 0.5 μg/μL validamycin, eggs blackened and clumped in the lateral oviduct, blocking release; treated females produced far fewer eggs by day 4, exhibited ovarian atrophy, shorter lifespan, and low hatchability. The expression levels of Vg and VgR in the ovaries of the fall armyworm were consistent with the changes in the ovarian developmental phenotype. Validamycin significantly inhibited the activity of trehalase in S. frugiperda, severely hindering their normal eclosion and lowering the potential reproductive capacity of S. frugiperda. Simultaneously, it directly affects ovarian development and the lifespan of female moths. The results provide data to support the development of new methods for controlling S. frugiperda.