# Repellency of Silver-Gray Plastic Film on Megalurothrips usitatus (Thysanoptera: Thripidae) in Cowpea (Vigna ungiculata)

## TL;DR

A silver-gray plastic film repels a damaging thrips pest on cowpea, offering a pesticide-free method to protect crops, especially during early growth stages.

## Contribution

The study demonstrates the effectiveness of silver-gray plastic film as a repellent for Megalurothrips usitatus in reducing pest damage on cowpea.

## Key findings

- Silver-gray plastic film repelled over 90% of male and 85% of female thrips in laboratory tests.
- Field trials showed significantly fewer thrips in film-covered areas during early crop growth and before/after flowering.
- Pest activity peaks in the morning and afternoon on sunny days, with the lowest activity around noon.

## Abstract

Megalurothrips usitatus is a serious crop pest in Southeast Asia and Hainan, China, and widespread pesticide use has led to resistance; a safe, environmentally friendly control is needed. The study tested whether silver-gray plastic film can alter the pest’s behavior on cowpea and reduce damage. Key findings: In the lab, the film repelled the pest, with over 90% repellency in males and about 85% in females. Field observations showed pest activity on sunny days peaks twice (7:00–9:00 and 13:00–15:00) and is lowest around noon. In yardlong beans trials, pest numbers in film-covered areas were consistently lower than in untreated areas during the early climbing stage and before/after flowering; during peak flowering the difference was not significant. The silver-gray film appears to be a promising, environmentally friendly method to reduce damage from this pest, especially in the early growth of crops. Wider use could lessen pesticide use, protect crops, and promote more sustainable agriculture.

Megalurothrips usitatus (Bagnall) (Thysanoptera: Thripidae) is a serious insect pest, causing severe damage to crops in Southeast Asia and Hainan Province, China. The misuse of chemical pesticides has led to high resistance in pests to many pesticides. Physical control is an alternative method that is environmentally friendly. We investigated the effects of silver-gray plastic film on the behavior of M. usitatus on cowpea (Vigna ungiculata). The observations of behavior found that the silver-gray plastic film has different repellent effects on female and male thrips, with a repellency rate of over 90% for male thrips, while it repels female thrips at a rate of 85% in the laboratory. Field surveys have found that the number of M. usitatus arrived at the first peak at 7:00–9:00 a.m., and then gradually decreased, reaching its lowest point by noon, and then gradually increased to reach the second peak at 13:00–15:00 p.m. on a sunny day. In the climbing period of yardlong beans, before flowering, despite the increasing numbers of thrips, we found that the number of thrips in the silver-gray plastic film hanging area was significantly lower than that in the control area. During the early and late stages of flowering, the number of thrips in the silver-gray plastic film hanging area was significantly lower than that in the control area, but during the peak flowering period, there was no significant difference in thrips numbers between the areas with silver-gray plastic film and the control areas. These results indicate that the silver-gray plastic film is a potential method to decrease damage from M. usitatus, especially in the early stages of crop growth.