reported that when
ozone treatment of grain included two applications of the ozone,
the first treatment allowed ozone to react with most of the grain
surface. With the second ozone application, the gas was not rapidly
degraded and moved through the grain more quickly, allowing the
ozone to kill the insects by reacting with them rather than with the
grain
referred to the decline in ozone decay
rate as the “passivation period”. Once “passivated” (Phase 2), ozone
degradation in the grain approaches first order kinetics
tested a modified screw
conveyor in order to increase ozone penetration and to reduce
“passivation period”, through better mixture and increase flow of
the grain. In that study, the authors noted that the application
through the screw conveyor system had no apparent change in CT
values regarding insect mortality. In this context, testing other
gases that will further shorten the treatment times of ozone,
especially the passivation period, should be regarded as a priority in
future research with ozone in stored grains
tested the efficacy of ozone flush treatment at 30-min intervals
for 5 h against life stages of E. kuehniella and T. confusum
placed at the top of 2 kg wheat. In this study, ozone flush treatment
resulted in almost complete mortality of all life stages of
E. kuehniella. In contrast, when E. kuehniella eggs were placed at the
bottom of 2 kg of wheat, mortality was extremely low. For
T. confusum, larvae placed in the bottom of 2 kg of wheat were
easily killed, but eggs, pupae and adults were found tolerant and
survival was high. In that study, the authors concluded that ozone,
unlike chemical fumigants, could not penetrate enough into the
commodity mass to kill the insects and therefore gaseous ozone
needs to be re-flushed intermittently to keep the required concentration
and control the insects. Similarly
in partitioned 70-cm grain columns with continuous
ozone flow, found that the longer the distance of the ozone input
the lower the mortality, regardless of the target species, which
indicates that the location from which the ozone is introduced into
the area that is to be treated is critical, as in the case of other aerial
insecticides (e.g. nitrogen)
noted that the presence
of wheat reduced the concentration of ozone by approximately 15%
as compared with the initial concentration at the input. Moreover
found that the insecticidal efficacy of
ozone was negatively correlated with the grain quantity, which is
directly related with the detrimental effect of the commodity to
ozone effectiveness. Additional experimentation is needed to
clarify the way to keep the ozone at sufficient concentrations at
various distances from the ozone source, emphasizing in better
penetration and shorter “passivation” intervals.