# Phototactic Changes in Phthorimaea absoluta Long-Wavelength Opsin Gene Mutants (LW2−/−) and Short-Wavelength Opsin Gene Mutant (BL−/−) Strains

## TL;DR

Researchers studied how tomato leaf miners respond to light and found specific wavelengths that can trap them without harming natural enemies.

## Contribution

The study identifies specific light wavelengths and opsin gene mutants that influence phototactic behavior in tomato leaf miners.

## Key findings

- 365 ± 5 nm light accurately traps P. absoluta without affecting natural enemies.
- LW2(−/−) mutants are attracted to 390 ± 5 nm light, while BL(−/−) mutants are unresponsive.
- Opsin expression is widespread in the body of P. absoluta.

## Abstract

The tomato leaf miner Phthorimaea absoluta is a harmful invasive pest first reported in China in 2017. As an alternative to chemical methods for pest control, recent research has focused on green prevention, specifically light-induced control. However, current light-trapping technology is non-specific, attracting both pests and non-target organisms. Our study aimed to understand the phototactic behavior of P. absoluta and to develop a targeted light-trapping technology. Using in situ hybridization, we found widespread opsin expression throughout the insect body. We also investigated tropism using a wavelength-lamp experiment, revealing that 365 ± 5 nm light accurately traps P. absoluta without affecting natural enemies. Additionally, we found that long-wavelength opsin gene mutants (LW2−/−) and short-wavelength opsin gene mutants (BL−/−) showed significant differences in phototactic behavior. The LW2(−/−) strain was attracted to light at 390 ± 5 nm, whereas the BL(−/−) strain was unresponsive. Our findings contribute to the development of precise light-trapping technology for controlling the tomato leaf miner, contributing to our understanding of pest population dynamics and the protection of crops from natural enemies.

Phthorimaea absoluta (Meyrick) is an invasive pest that has caused damage to tomatoes and other crops in China since 2017. Pest control is mainly based on chemical methods that pose significant threats to food safety and environmental and ecological security. Light-induced control, a green prevention and control technology, has gained attention recently. However, current light-trapping technology is non-specific, attracting targeted pests alongside natural enemies and non-target organisms. In this study, we characterized the phototactic behavior of tomato leaf miners for the development a specific light-trapping technology for pest control. In situ hybridization revealed opsin expression throughout the body. Furthermore, we investigated the tropism of pests (wild T. absoluta, Toxoptera graminum, and Bemisia tabaci) and natural enemies (Nesidiocoris tenuis and Trichogramma pintoi) using a wavelength-lamp tropism experiment. We found that 365 ± 5 nm light could accurately trap wild P. absoluta without trapping natural enemies and other insects. Finally, we analyzed the phototactic behavior of the mutant strains LW2(−/−) and BL(−/−). LW2 and BL mutants showed significant differences in phototactic behavior. The LW2(−/−) strain was attracted to light at 390 ± 5 nm and the BL(−/−) strain was unresponsive to any light. Our findings will help to develop specific light-trapping technology for controlling tomato leaf miners, providing a basis for understanding pest population dynamics and protecting crops against natural enemies.