Posted: 28/09/2013 at 18:03
Some seeds will be infected on the plant. Granary weevils bore into fruits and seeds and lay an egg in the seed. The larvae develop and pupate within the seeds. It only needs one infected seed in a batch, in an enclosed area, the new weevil will then lay eggs on further seeds, etc. A sack of seed, put away in a dry encosed place can be totally destroyed.
If you put one of the slow release insectides, such as those used to kill wardrobe moths, in the tin,with stored seed, this should prevent further infestation.