The war against pantry moths & their evil offspring, the weevil.
Every year when it begins to get warmer, I start waging a war against pantry moths and weevils. Having lived in humid Auckland, New Zealand and before that humid Sydney, Australia, we've clashed many times.
Here's some advice and tips I've picked up that might help you.
Get ahead of the curve:
By this I mean don't wait until you have a problem. Act now. I promise you that by the time you pick a packet up and go "what's that webbing stuff in the corner?", they're already entrenched and nibbling their way through your entire pantry! Believe me, you do not want to have to be throwing it all out as you slowly realise the extent of your outbreak. I've been there, and it's wasteful, expensive, and very disheartening.
Female pantry moths can lay 400 eggs in 2 weeks...I rest my case.
Do these things right now:
1) Spread dried bay leaves every 50cm or so around your pantry, on all the shelves. This is really effective as they simply hate the smell. Replace when they don't appear to have a smell anymore. You can even drop them into your containers.
2) Get a packet of pheromone sticky traps for pantry moths from your supermarket, like this one.
As my war is bad, I have one open on each shelf, but you might find one is enough. Change them every 2 months or according to instructions. If you trap one, take it is a warning that it's time to take these other steps.
Tip: Hide them at the back so you're not staring down death every time you reach for the pasta!
3) Start storing EVERYTHING in see-through containers. This has a double benefit of a) you'll be able to spot them and vitally, b) you'll be able to contain an outbreak to just one container. These critters like just about all of our pantry content, such as flour, breadcrumbs, cereal, grains, nuts, dried fruit, pasta, cous cous, spices, rice, biscuits, bread, cake mix, dog food, I've even seen them in sugar. There's things they like more than others, such as flour and grains, but I've witnessed how they refuse to discriminate, not turning their noses up (I recognise they don't have noses) at anything.
NOTE: not all containers are weevil-proof! See my notes below
4) Unpack groceries and put pantry items, as mentioned above, straight into containers. A lot of infestations are brought home from the supermarket. They burrow into sealed packaging. Get checking for signs. Look for sticky clumps in the middle of flour and grains. Look for webbing at bottom of packets once you've poured out the contents. Webbing also appears inside the packet, hanging in the corners. Look for wriggling weevils, they often collect on the bottom so shake the contents around and look up from underneath. Don't bother looking for the eggs, they're way too small to spot.
5) As you unpack, freeze high-risk items if you can. This kills the eggs, which at least stops the life-cycle. I tend to only freeze flour packets as these are usually the main culprits. It's just not practical to freeze every item they like to munch on, (who's got time for that, right?) so just do what you can. Some people say freeze overnight, others 2 days, but I find 2 hours has been enough.
6) Throw away any adulterated packets. Bag them up tight and put them straight into outside bin. Better to lose one packet of grains now than the whole pantry later.*
*Or of course, you can choose to still eat the food as the eggs/weevils/moths are harmless to ingest, and we all know we're eating insects and crud already that got caught up in the food production cycle anyway, right? If you shuddered at that, I suggest you do NOT read the FDA's Food Defect Action Levels publication where it specifies chocolate is allowed to contain up to 60 insect parts per 100 grams, shredded carrots are allowed to contact 800 or more insect parts per 10 grams, tomato paste is allowed to contact 2 maggots for every 100 grams...& I'm not even going to mention that chocolate is also allowed to contain 1 or more rodent poo per 100 grams...or the allowed levels of mould, rat hairs etc. (Oops, I guess I just did). Europeans/UK are not perfect either, they just have a due diligence view for prosecutions i.e. as long as you tried your best...
7) I sometimes soak cotton balls in an essential oil like like peppermint, citronella, tea tree or eucalyptus and scatter them around the cupboard too. I haven't tried this on it's own, but rather as a throw-the-kitchen-sink-at-it solution.
My 'learnt-the-hard-way' tips for getting the right storage containers:
In my (bitter) experience, not all storage containers will keep the weevils out (or in, depending on the situation).
Here's a quick gallery of the types that I use every day because they work:
1st photo: Vacuum seals always work. Even if the buttons get trapped open, weevils only end up trapped in the lid and not in the food. 2nd: Deep twist tops like the middle photo of a glass container also work. 3rd: Pressure-sealed containers also always work. 4th: Hard, thick plastic packaging like the right photo will also work (until it's opened, of course). I've never had a weevil get through any of these.
It doesn't matter if you prefer plastic or glass versions.
What has failed me in the past:
1st photo: Thin twist tops like this do not work at all. 2nd: Kitchen pressure ties are also a fail. 3rd: Thin plastic packaging (& paper packets like flour) will also let them in.
Regular jam jars definitely do not work.
Take it from me: 1) lids are only any good if closed properly (made that mistake!) 2) other family members will never take the lid-sealing mantra as seriously as you do, so you'll have to keep pressing the importance upon them...
Always go for see-through so you can monitor for any activity. Pick up the containers every now and again and look up from underneath. Shake a little.
I appreciate buying enough storage containers is an expensive undertaking - I have also used double plastic bags as alternatives - really it's anything to stop the spread.
If you have an infestation:
1) Discover the source. Bag up and throw it out. Same for anything infested.
2) Wash all your containers in hot, soapy water.
3) Wipe all your cupboard with vinegar or an essential oil.
4) Start again, following the earlier steps.
5) We try not to bulk buy large-sized flour packets now. I only buy enough to fit in a container or two. Means you're throwing out less if you have to, and are able to keep a closer eye on any activity inside the containers.
Pantry moth life cycle:
Eggs are tiny, round and white. They take 7 days to hatch. It's unlikely you'll see them, as they're that small.
Larvae hatch and live for 2-3 months. They're usually cream with a dark head, up to 2cm long, (but can change colour according to their food source). They wriggle and have feet.
Pupa are cream and often wrapped in webbing. Often found in dark, high corners and behind the pantry door. They'll hatch after 15-20 days.
Moths are 1cm long and a light grey colour with the wing tips a bronze colour. Easy to squash with a hand as they are groggy and slow. They do not eat - their only goal is to reproduce and lay more eggs.