The Grain Weevil – Sitophilus granarius
The adult weevil is a small (2.5-4mm) and brown insect. They are very noticeable with their long snout and elbowed antennae. The elytra are unmarked and the chest has oval punctures. It cannot fly as the wings are too small.
Grain or Wheat Weevils are very common pantry pests in Ireland. They are thriving in high humidity and temperatures (optimum temperature is 30 º C). They live for about one year. Under ideal conditions, the development from egg to adult takes 25 days, but on average it takes around 2 months.
Larvae develop hidden inside the grain. Usually, there is no external sign of infestation until after about a month when the grown weevil chews through the seed shell to get out. Females lay eggs after 2 weeks and in total, this represents 150 to 300 eggs.
As the name indicates the Grain Weevil is a very common pest in stored grain. In Northern Ireland, a survey showed that 12% of local farms are affected by the granary weevil. The weevil is usually feeding on wheat, barley, rye, oats, corn, and also rice. It also infests pasta and flour. In houses infestations usually arise from bird seeds.
Grain weevils ressemble Rice Weevils (Sitophilus oryzae) who have four distinctive light coloured dots on their back. These similar weevils are usually coming out of wholegrain rice bags but are also infesting other dry foods in houses.
If you notice grain weevil activity in your house you should inspect your food presses immediately and discard the damaged items. To get rid of remaining weevils, check our DIY insect-killing products here.