A group of researchers from South Carolina State University has discovered that using ozone treatment may serve as a substitute for controlling various life stages of particular stored-product insect pests. This could result in a decrease in the utilization of other chemicals and subsequently lower the environmental and health risks related to those chemicals.

Every year, stored-product insects cause millions of dollars in damages to long-lasting commodities like grain, legumes, dried fruits, nuts, spices, and grain-based products. Typically, infestations of insects in bulk grain are controlled by means of fumigants and insecticides that come in contact with the insects.

Ban of Methyl Bromide Prompts the Search for Alternatives

Due to the prohibition of methyl bromide, which was the most effective fumigant for controlling stored-product insect pests, the quest for alternative control options has become imperative. Phosphine fumigation is another approach for managing stored-product insects, but its frequent and unselective utilization has led to the emergence of resistant populations and ineffective control. As a result, the food and feed industries are persistently seeking effective alternatives for pest management, particularly those that are environmentally friendly.

The inherent benefits of using ozone to manage insects and molds linked with grain have garnered the attention of researchers. Ozone is a noxious gas that has demonstrated its effectiveness in killing insects and breaks down swiftly to molecular oxygen in atmospheric conditions. Consequently, ozone can be utilized securely and efficiently in food processing industries to eliminate insect infestations.

During the reporting period, Dr. Rizana Mahroof’s project, funded by NIFA and who is currently the National Program Leader in NIFA’s Division of Community and Education, centered on evaluating the impact of ozone on two significant stored-product insect pests. The pests in question are the red flour beetle and the Indian meal moth, both of which have economic importance.

In an earlier study, the research team assessed the dose-time-response criteria for the most resilient life stage of the two insect species. They tested various ozone concentrations and exposure durations on the eggs, larvae, pupae, and adults of both species. Using this information, subsequent experiments were conducted to test the most resistant life stage. The findings revealed that eggs of both species were difficult to eliminate.

To continue the investigation, the researchers selected five construction surface materials on which to place the eggs of the red flour beetle and the Indian meal moth. The goal was to assess the efficacy of ozone on different surfaces during the most resilient life stage.

NIFA’s 1890 Capacity Grants Program supported this project, which suggested that significant mortality rates in insects may require high concentrations of ozone and extended exposure periods to the gas. The studies revealed that an insect’s susceptibility to ozone varies depending on its life stage. Certain stages are more vulnerable to ozone exposure than others.

Several Factors Influence the Susceptibility of Eggs to Ozone

In general, the research has demonstrated that the susceptibility of eggs to ozone gas depends on the dose, exposure time, species, and the presence or absence of food during treatment. Additionally, the study found that typical construction materials utilized in grain bins, mill equipment, and processing and storage plants absorb a negligible amount of ozone gas, thus permitting its utilization in these facilities.

Establishing industry guidelines for treatment requires identifying tolerance levels for all species of stored-product insects. The effectiveness of ozone gas may differ depending on the packaging materials utilized to package value-added products. Hence, additional research is required to assess the susceptibility of insects to gaseous ozone, particularly those that were not previously studied, as well as the typical flow and penetration of ozone through various packaging materials.

In both the presence and absence of food in the testing environment, eggs exposed to ozone failed to hatch when compared to corresponding controls. The toxicity of ozone was not affected by the type of surface it was applied to, and the mortality rate remained high, exceeding 95% for all surfaces. This research indicated that construction materials composed of aluminum, wood, concrete, vinyl, or glass exhibit similar reactions to ozone. These surfaces do not absorb a substantial amount of the gas, allowing ozone to react with the insects.