Leaky seams of paper seed-, food-, and feedbags invite attack by stored product pests

Larger quantities of plant seeds, food and animal feed products are often packed into multi-layer paper-bags. When the bags are sewn at the top, the seams pose a threat concerning stored product protection: Where the needle punctured the paper, the thread often does not fill out the hole but leaves an opening. This attracts female stored product moths and beetles for oviposition and is sufficient for minute neonate larvae to enter into the stored good following the cue of attractive volatiles. Industry complaints in Germany seem to have increased during recent hot summer periods. Heavily infested paper bags and an increase in humidity allowed additional species their development such as dust lice. In a laboratory test with sewn seed bags, eggs and neonate larvae of the Indianmeal moth Plodia interpunctella (Lepidoptera, Pyralidae) were found next to the seam. Holes were approximately 1 mm in diameter while the thread only covered 0.2–0.3 mm. This is sufficient for larvae to enter. As infestation pressure is prone to rise due to global warming, preventive action is required. Pest-proof packaging could help to avoid losses and guarantee product quality on the way from producer to consumer. Instead of a seam, the opening of a paper-bag could be glued shut. The glue should cover all bag circumference in order to provide a complete barrier against larval movement, as glue points would still leave openings for insect larvae to enter. For bags that require the seam or gas exchange, additional options are discussed in this paper.