# Development and Population Growth Rates of Sitophilus zeamais (Coleoptera: Curculionidae) Exposed to a Sublethal Concentration of Essential Oil of Piper hispidinervum

## TL;DR

This study shows that a plant-based essential oil can reduce the growth and reproduction of a corn pest, offering a safer and more sustainable pest control option.

## Contribution

The study explores sublethal effects of Piper hispidinervum essential oil on maize weevil populations, revealing its potential for integrated pest management.

## Key findings

- Sublethal exposure to the essential oil reduced development rates and population growth in three of four tested populations.
- The safrole compound in the oil broke down quickly, reducing food safety concerns.
- One population showed no significant response to the treatment, indicating variability among populations.

## Abstract

Insects that damage stored grains, such as corn, cause major losses for farmers and food producers around the world. Finding safer and more sustainable ways to control these pests is a growing concern. In this study, we tested the effect of a sublethal concentration of essential oil extracted from a plant called Piper hispidinervum on a common grain pest known as the maize weevil. We observed whether this plant oil, even at doses that do not kill the insects immediately, could affect their ability to grow and reproduce over time. We tested four different insect populations and also checked how long a natural compound from the oil remained in the corn after treatment. The results showed that the essential oil reduced the number of insects that developed in most populations. One population, however, was not strongly affected. We also found that the only safrole that was studied in the oil broke down quickly, leaving only a very small amount after some time, which is good news for food safety. The results highlight the potential of plant-based essential oils to complement the existing pest control methods in stored grains, promoting safer and more sustainable management practices.

Essential oils have emerged as promising alternatives for pest insect control. However, sublethal effects on insect reproduction and development are rarely explored, despite their relevance to integrated pest management (IPM). This study evaluated the sublethal effects of Piper hispidivervum C. DC. essential oil (EOPH) on the development and population growth of four populations of Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), as well as the persistence of safrole residue in treated corn grains. Population development rates were determined using emergence curves and total emerged adults, while population growth was assessed by counting live insects in the feeding substrate at different storage intervals. Safrole residue persistence was analyzed using solid-phase microextraction in headspace mode (SPME-HS). Sublethal exposure to EOPH significantly reduced the development rate, total emergence, and growth in three of the four populations. The population from Crixás, GO, showed no significant reduction, with a population curve overlapping the control. The lethal dose was reduced by 98.20%, indicating low persistence and potential food safety. The EOPH exhibited sublethal effects on S. zeamais populations, reducing both development rates and population growth. This reduction varied among the populations studied. Further research is encouraged to explore its effects on different insect populations and under broader environmental conditions.