You open your favourite box of cereal, the milk is ready, and you’re about to have a tasty breakfast when you see it… weevils! Now that you’re older you get the same disappointment from opening a bag of malt that has been standing in the garage for some time. You don’t really want to throw it away, and guess what? You don’t have to! Depending on your infestation degree, you do not have to throw out your grains, necessarily. To some level, your beer won’t be harmed by weevils.
When to chuck your grains:
If your bag of grains is walking away by itself or the colour of your grain bag has changed then I’d say get rid of it. If you see more weevils than grains… chuck it!
If there is an unpleasant odour then I’d chuck it because that odour may just end up in your beer.
When NOT to throw it away?
A few weevils will not harm you, bugs will be pasteurized in the boiling process and will not alter your beer’s flavour.
If you notice it in the early stage of infestation, you should be fine because they have not eaten all the worth of your grains.
Weevils and ants will rise to the top of your wort so it should be easy to scoop them out if you do not like the sight of them in your wort.
How to prevent weevils?
The best way to prevent getting weevils is to use your stock before they are infested.
Another option is to freeze your stock, which will kill the weevils but not the eggs.
Add Diatomaceous Earth to your grains and sprinkle it around the container that your grains are in to prevent them from travelling to your other stock. Diatomaceous Earth is pet and human-friendly and will not affect your beer in any way. DE will dry out the weevils and slowly kill them, harshly, but if not, they will eat up your grains and find their way to your next bag!
Another method is to suffocate the weevils. The long and cheap process is to place them in an airtight container. The quicker option that might be a bit pricey is to smother them with CO2.
Where can you purchase it?
Of course, your favourite brew shop has some! At only R60/kg, just ask in store
A few pet shops might have it since some people feed it to their dogs.