Ozone is a gas that is highly oxidizing and is used for disinfection in other situations. Microorganisms are, for example, very sensitive to low concentrations of ozone. The advantage is that ozone is an unstable gas and quickly converts to the oxygen molecule (O2), which is harmless. The ozone is produced in situ by an electric high-voltage process and can be used in, for example, a grain silo.
One of the aims of the research was to examine how effective ozone is at different development stages of the insects and find the best combination of dose and duration of treatment. The scientists looked at the effect of ozone on 11 different species of insects that cause damage in dry stored products. Past studies have only looked at the effect on insects that were freely exposed to ozone, but this project included the insect stages developing inside the grains.
They looked at the effect of different temperatures and the physiological effect of ozone by examining the level of oxidative stress and the transcription of the genes involved in the insects' natural defenses against oxidative stress.
The scientists found that in order to kill all the bugs that live freely among the kernels, they had to use 35 ppm ozone for six days. If the stages of the insects living inside the kernels had to be eradicated too, they had to use 135 ppm ozone for eight days.
There are variations in the amount of ozone needed to control the distinct stages and types of pests: adult insects are generally more sensitive to ozone and often die after treatment with 25 ppm for five days. There is also a variation in the sensitivity for the internal stages, but to eradicate all stages, the high dose of 135 ppm for eight days is used.
(Flygoo Ozone Generator Used for Grain Killing Inserts in Nicaragua)