Abstract
Hermetic storage is of interest to farmers and warehouse managers as a method to control insect pests in small storage facilities. To develop improved understanding of effects of hermetic storage on insect pest activity and mortality over time, oxygen levels, acoustic signals, and observations of visual movement were recorded from replicates of 25, 50, and 100 adult Sitophilus oryzae (L.) (Coleoptera: Curculionidae) hermetically sealed in 500- and 1,000-ml glass jars. Recordings were done for 28 d; twice daily for the first 6 d and twice weekly thereafter. Insect sounds were analyzed as short bursts (trains) of impulses with spectra that matched average spectra (profiles) of previously verified insect sound impulses. Oxygen consumption was highest in treatments of 100 insects/500-ml jar and lowest in 25/1000-ml jars. The rates of bursts per insect, number of impulses per burst, and rates of burst impulses per insect decreased as the residual oxygen levels decreased in each treatment. Activity rates <0.02 bursts s−1, the acoustic detection threshold, typically occurred as oxygen fell below 5%. Mortality was observed at 2% levels. The time to obtain these levels of insect activity and oxygen depletion ranged from 3–14 d depending on initial infestation levels. Acoustic detection made it possible to estimate the duration required for reduction of insect activity to levels resulting in negligible damage to the stored product under hermetic conditions. Such information is of value to farmers and warehouse managers attempting to reduce pest damage in stored crops.
Highlights
Hermetic storage is of interest to farmers and warehouse managers as a method to control insect pests in small storage facilities
The significance of the interaction term indicated that each treatment showed significant differences in the rate of decline of O2 throughout the storage period; analysis of variance (ANOVA) was carried out to determine the statistical significance of differences on days 1, 5, 15, and 25 (Table 1)
Our study employed the use of acoustic technology to explore activity trends of S. oryzae in hermetic storage conditions
Summary
Hermetic storage is of interest to farmers and warehouse managers as a method to control insect pests in small storage facilities. The time to obtain these levels of insect activity and oxygen depletion ranged from 3–14 d depending on initial infestation levels Acoustic detection made it possible to estimate the duration required for reduction of insect activity to levels resulting in negligible damage to the stored product under hermetic conditions. Such information is of value to farmers and warehouse managers attempting to reduce pest damage in stored crops. A second method, the use of sealed, gas-impervious hermetic enclosures, is of increasing interest in locales where high levels of infestation are prevalent in smallscale storage facilities (Tefera et al 2011, Murdock et al 2012, De Groote et al 2013, Martin et al 2015, Williams et al 2017). S. zeamais infestations often begin in mature crops in fields before harvest (e.g., Adedire 2001)
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