Paper-bag seams of seed-, food-, and feedbags: An invitation to attack by stored product pests

Abstract: Larger quantities of plant seeds, food and animal feed products are often packed in
multi-layer paper sacks. When the sacks are sewn at the top, the seams pose a threat concerning stored product protection: Where the needle punctured the paper, the thread 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 seem to have increased during recent hot summer periods. Heavily infested paper sacks and an increase in humidity allow additional species their development such as dust lice and mites. As the risk of infestation is prone to rise due to global warming, preventive action is required. In a laboratory test with sewn seed sacks, eggs and neonate larvae of the Indian meal moth Plodia interpunctella (Lepidoptera, Pyralidae) were found next to the seam. 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 sack could be glued shut. The glue should cover all sack circumference in order to provide a complete barrier against larval movement, as glue points would still leave openings for insect larvae to enter. Other options could be to cover the seam with a broad adhesive tape, to apply a flexible varnish onto seam and adjacent paper or to use a thick and fluffier thread that fills out holes completely. In products that require gas exchange, permeable membranes could replace seams without giving access to pest invasion.