# An Internal Marking Method for Adult Spodoptera frugiperda Smith Using an Artificial Diet Containing Calco Oil Red N-1700

## TL;DR

Researchers developed a safe and effective method to mark adult fall armyworms using a red dye in their diet, aiding in tracking their migration patterns.

## Contribution

A novel internal marking method using Calco Oil Red N-1700 was developed for Spodoptera frugiperda adults without affecting their biology.

## Key findings

- A 0.2% concentration of Calco Oil Red N-1700 in the diet effectively marked FAW adults without altering biological indicators.
- Marked FAWs showed normal development, reproduction, and flight ability comparable to unmarked controls.
- Distinct red or pink markings persisted for at least 5 days in females and 9 days in males.

## Abstract

Spodoptera frugiperda Smith (fall armyworm; FAW) (Lepidoptera: Noctuidae) has invaded and spread across Africa, Asia, and Oceania for several years. Conducting mark–release–recapture (MRR) experiments will help clarify the migration behavior and patterns of the FAW in newly invaded areas. Therefore, we researched a suitable internal dye marking method for the FAW by incorporating different concentrations of Calco Oil Red N-1700 into an artificial diet. The biological indicators (developmental duration, reproductive parameters, flight ability, etc.) of the FAWs fed a diet containing a 0.2% concentration of Calco Oil Red N-1700 were normal, and both female and male adults exhibited clear marking colors. This study can promote the development and application of MRR experiments for the FAW, and will help formulate effective pest management strategies.

As a migratory invasive pest, Spodoptera frugiperda (fall armyworm, FAW) has recently posed a serious threat to food security in newly invaded areas (especially in Africa and Asia). Understanding its migration (or dispersal) patterns in newly invaded areas is crucial for regional forecasting and management efforts. By screening an appropriate marking technique to conduct mark–release–recapture (MRR) experiments, the migration patterns of the FAW can be effectively studied. In this study, we added different concentrations of Calco Oil Red N-1700 (an oil-soluble marker) to a self-made artificial diet and assessed the rearing and marking efficacy. The results indicated that a concentration of 0.2% of Calco Oil Red N-1700 in the diet was optimal for marking adult FAWs. The biological indicators (e.g., developmental duration, reproductive parameters, and flight ability) of FAWs fed this diet were basically consistent with those of FAWs fed a normal diet, with a larval stage of 15.46 days, a pupal stage of 9.81 days, a pupal mass of 278.18 mg, an adult longevity of 15.41 days, and an egg deposition count of 1503.51. Meanwhile, the flight distance, duration, and velocity were 24.91 km, 7.16 h, and 3.40 km/h, respectively (12 h tethered-flight tests), without difference with the control. Females and males exhibited distinctive marking colors (red or pink) that persisted for at least 5 and 9 days, respectively. This study developed an economically effective internal marking method for the adult FAW, laying the foundation for conducting MRR experiments. This will help clarify the migration behavior and routes of the FAW, providing a scientific basis for formulating effective pest management strategies.