I dust with cinnamon!! It's a good fungicide and stem rot is the only problem I have in storage. I think you might have to experiment and see what works best in your conditions.

Have you tried Bleach? Ordinary domestic bleach diluted 5ml to 1 liter with water is effective for fuchsias and would be worth a try. Wear eye protection and rubber gloves

Oh boy. I'm not good with metrics. Would that be like a cup to a gallon? Or, a half cup?
Cinnamon sounds very interesting. Would that attract mice in my crawlspace? If it works for you, it should work for me too!

I am not conversant with cups. I reckon 4 cups water should be about 1 liter, which weighs 1kilogram or 2.2 pounds, to this amount of water add 1 teaspoon bleach, mix and immerse plnts briefly.

October, I wont comment on the bleach or any other amendment that is supposed to keep plants from harm...but...such treatment is not necessary if....

if you can keep your lifted plants dry, and cool...in a place where light is kept from, where the temperature is constant in the range of 40 to 50 F, you stand a good chance of seeing every plant come back next spring.

I think though, washing the roots and/or plants is not necessary either. Just knock off the excess soil from the roots and let them sit in your garage ....up off the floor, for a day or so, then taken to that crawl space where the plants will remain...untouched, unwatered, unlighted, unheated...until we wish to re-invigorate them in mid February. The onlly problem I see with boxing them, is if one plant is infected with ????....it could so easy affect other plants. It would be much better to separate each plant, hang them up independently or ...bag them in large Kraft paper bags...left open for good air circulation...until mid February.

At that time, they are brought out, cut back to about 4", their roots teased and inspected for damage, all leaves and damged parts of the plants are removed.

Into new potting soil (mixed with peat moss and coarse sand if wished to increase drainage), clay pots are good, given the best sun you can find....south, or west..or east...
watered well until drainage is seen, allowed full drainage, then the excess dumped.

Then no further watering is done until new growth is evident. Resume normal watering, allowing the top 1" to dry down between waterings....and always, water until drainage is seen in the saucer.

Do not feed until new growth is evident, then 1/2 rate every 3rd or 4th watering with 20/20/20. Turn the plants 1/4 turn every day to ensure all parts of the plant receives equal light.

In about 6 weeks, there should be much new foliage...and ..depending on how good the light is, flower buds might be seen.

Washing the plant only sets back the time they go into storage. Never store a wet plant....that could iniitiate mildew and mold.
The plants in the cool space, should never be watered...not even a bit...after all, what would you be watering.
They shouldn't be given light....light initiates growth....how much growth can happen in a dark room.
They should be kept cool....cool temps diminish the plant's ability to grow.

We don't want them to grow...until we want them to..in February.

We put them to bed last weekend. We used those large yard waste paper bags. They are about 3 1/2 - 4 feet tall. There are nine bags, each has 3-4 plants in it. I stapled them shut to keep out the light. We are storing them in a cool crawlspace where the light is seldom turned on. Should I open the bags for air? I had trouble closing a couple of them because the plants were taller than the bags!
I only kept them once before in a bag. It probably wasn't cool enough. Anyway, come spring, they were covered with mealy bugs. We have since moved and have not seen any mealy bugs around here.
Another question I have is that, with this many huge plants, we won't be able to pot them up in February. Will they last until May when we can plant them outside? Will they leaf out and catch up fast?