Seed mites

[rowanseeds]

Seed mites are something that many seed savers aren't aware of but are very important as they can destroy your stored seeds very quickly.

In my experience they mainly attack brassica and cucurbit seeds the most and you should keep your seeds in clear containers (I use small plastic honey jars from Ebay, but jam jars are fine, so you can easily see the damage before it gets serious.

Seed mites are very difficult to see with the naked eye unless your eyesight is very good, but if you have them you'll see a fine brown or grey dust in the bottom of your jar. As soon as you see it you have to do something or your seed will be wasted. The two methods I use to kill them are 1, freezing the seed for a couple of days or so (never freeze your seed more than once, and never put back in the freezer if the seed is even slightly thawed), or 2, spray the inside of the jar lid with fly spray (if you aren't certified organic) and then shake the seed to give it a slight coat. The fly spray evaporates pretty quickly so you shouldn't smell it after a couple of days or so if you open the jar. I haven't found diatomaceous earth to be particularly effective, probably because they're too small to be affected by the sharp edges.

The main reason you get seed mites is storing your seed before it's fully dry. It will be dry enough to keep without rotting, but contains just enough moisture to feed the mites. This is why you should always wait another week before storing after you think it's dry enough. They can appear out of the blue at any time so always be careful and check your seed often.

[Bega Liz]

That is really interesting. I've seen the 'dust' in the bottom of occasional jars but didn't realise that mites were the culprit. I always just thought 'insect' and wondered why I never actually saw the culprit. (Yes I do know I need glasses).
We've put our jars through the freezer as a standard process for years now, but I have still occasionally seen the dusty stuff at the bottom. I will have to pay closer attention in future and see if somehow those jars missed a trip through the freezer or whether something else is going on.
I have also seen a kind of cobwebby clinging together of clumps of seed, but not since we started freezing the seeds. It seems to happen really easily with lettuce seed if we don't do anything.
Have you ever tried the solarising trick to remove pests rather than freezing?

[rowanseeds]

I'm not sure what you mean by solarising the seeds to remove seed mites. I assume that you mean exposing to sunlight as solarising, but that is pretty bad for seed germination. If you mean something else please let me know as I would be interested in checking it out.

[Bega Liz]

If you have a look at the 'Controlling Pests in Seed' thread there is an explanation of solarisation there. Like you my immediate response was 'that would be bad for the seed'. But Jon sent me the following links to support it -

https://storedproductinsects.com/biolog ... festation/

https://academic.oup.com/ae/article/37/4/228/2474348

I suspect that there are some seeds it would be really bad for but there isn't enough information in those links to help figure out which things it definitely wouldn't be good for. For people in really humid areas that have a lot of trouble drying seed enough to make them safe to freeze it could be a really useful alternative method.

[MBMSS - Lloyd]

I'd recommend looking to hot water treatment of your seeds when harvested.
If done correctly you will likely also kill a vast number of other insect pests at the same time as killing Bacterial and Fungal pathogens.

There are some basics listed in the Book from Arche Noah and Pro Specie Rara - 'The Manual of Seed Saving'.

Have a look here for examples:

Vegetable seed treatments
WA Department of Primary Industries.
https://www.agric.wa.gov.au/vegetables/ ... page=0%2C1

Seed disinfestation strategies for saved pumpkin and squash seed
Ontario Ministry of Agriculture
http://www.omafra.gov.on.ca/english/cro ... rt15a6.htm

[Arian]

I've been thinking of trying hot water treatment for brassicas in particular. Thanks for the link, Lloyd, very useful. Will report back... And I really agree with your point, Rowan about waiting even longer when you think seed is dry. As long as the seed doesn't get baked or fried, air drying isn't going to hurt it and it's better to be safe than sorry. It also suits my lazy approach to seed saving where I just leave things in paper bags and on towels endlessly while I forget to do anything with them!