Detection of grain infestation caused by the granary weevil (Sitophilus granarius L.) using zymography for α-amylase activity

• Amylases of grains have different properties compared to granary weevil.
• Detection of granary weevil hidden infestation is possible by zymographic assay of α-amylase.
• Zymographic assay detects amylases secreted by Sitophilus granarius larvae, pupae and adults of both sexes.
• It is possible to detect traces of infestation of kernels even after one day feeding of granary weevil.

Granary weevil infestation in wheat kernels is difficult to detect since the insects cause a hidden infestation by developing inside the grain. In order to identify an early infestation of stored wheat, a technique involving electrophoresis combined with zymographic assay of α-amylases has been developed. The concept of the method is based on the differences between the electrophoretic mobility of amylases present in wheat kernels and those secreted by the insect's digestive system. The diagnostic accuracy of the method developed was compared to expert scoring, based on microscopical observation. It is proposed that zymographic assay of α-amylases, which does not require either expensive equipment or chemicals, is a suitable method for the accurate detection of granary weevil α-amylase even if beetles are only present on grain for a very short period of time such as one day.