Evaluation of hermetic and non-hermetic plastic bags for grain storage against Rhyzopertha dominica (Coleoptera: Bostrichidae): infestation resistance and fumigation efficacy

Infestation resistance of hermetic plastic (HB) bags and non-hermetic polypropylene (PP) miniature bags for grain storage was studied against Rhyzopertha dominica (Fabricius) (Coleoptera: Bostrichidae) under conditions simulating both external and internal infestation. Results showed that R. dominica successfully penetrated PP bags of 0.02–0.05 mm thickness but failed to perforate HB bags with 0.07 mm thickness. Externally released R. dominica caused grain weight loss in penetrated PP bags, while R. dominica surrounding HB bags experienced 100 % mortality. When R. dominica were released internally, HB bags again caused the highest R. dominica mortality (97 %) and the least grain weight loss (0.57 %), whereas PP bags caused significantly lower R. dominica mortality and greater grain damage (1.13–1.32 %). Despite the superior performance of HB bags to protect grains against R. dominica , overall results indicated that internal infestation caused lower mortality and greater grain losses than external infestation. Phosphine fumigation for internal infestation of these bags showed R. dominica mortality of 89–94 % in PP bags and 98.67 % in HB bags. However, high R. dominica mortality in HB bags even without fumigation indicated the inherent contribution of hermeticity to pest suppression. To simulate long-term field storage, bags were artificially damaged with two holes per bag. Fumigation of damaged bags showed 89–100 % mortality of R. dominica in PP bags and 100 % in HB bags. In the corresponding non-fumigated control treatment, R. dominica mortality in damaged HB bags was only 14 % and 2–5 % in PP bags. These results highlighted the importance of phosphine fumigation, which becomes essential for internal infestation in PP bags and for HB bags when their hermeticity is compromised.