Paper sack seams of seed-, food-, and feed-sacks: An invitation to attack by stored product pests

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.