Continuing the series on the nasty unwelcome visitors that occasionally dare to invade our treasured greenhouses and inflict such devastating damage in the process, today I've got a more hopeful tale to tell.
Let's see how we actually can avoid having any problems at all next year by putting in some effort now, as the season is coming to an end.

Your fuchsias will benefit from a spell outdoors in late summer (if not already there anyway) as it will greatly assist the ripening of the wood to improve their chances of a successful over-wintering, There is a lot is to be said for the traditional method of letting the plants, go right through their full growth cycle and then have a complete rest period, nature's intended way.
Plants grown on the biennial system, kept in green leaf during winter, slowly growing on or just ticking over, won't mind a period outside either. It will result in firmer, short-jointed growth and development of a sturdier framework so beneficial later on to support the masses of blooms!

The key to having your plants pest free during the summer really lies with having your plants clean to start with in spring, having them come out of the winter in a clean, healthy condition.

With the greenhouse completely empty we now embark on a thorough cleaning spree. Remember, adult red spider mite e.g. over-winter in crevices in your greenhouse structure and vine weeevils hide amongst the debris under the benches etc.
Wash down the glass thoroughly, but also the glazing bars including all the awkward channels and all the staging and benching, with a good sterilant agent such as Jeyes Fluid, though some people now prefer Armillatox.
Fumigation can also be carried out now, using sulphur candles. This permeates into the various cracks & crevices killing over-wintering pests there and the spores of mildew as well.
Also clean the outside of the glass, to allow as much light as possible to reach your over-wintering plants, which helps to avoid weak and leggy growth which would be more prone to fall victim of pests or diseases.

Before returning your plants to your spic and span greenhouse, make sure they are clean, pest-free, too!!
Remove all foliage, or let nature take it course and do this for you with a mild frost, and spray with or dip the remaining framework into a combined fungicide/pesticide solution first.

If you suspect vine weevil grub damage (plants hardly anchored in their pots) repot them now, removing and disposing of all old compost and grubs. (full repotting procedure)
The biennial plants, in green foliage, must particularly be thoroughly inspected and again sprayed or completely dunked into the fungicide/pesticide solution.
Remember it is imperative to come out of the winter with clean plants, so don't fill your greenhouse now with suspect plants!
IF IN DOUBT, JUST CHUCK IT OUT.
During the winter months frequently check over your plants, the big campaign is to eradicate pests and diseases now
Be vigilant at all times, paying great attention especially to the undersides of the leaves and the growing tips.
It is relatively easy to get rid of a few intruders by simply squashing them between fingers and thumbs during the daily/weekly inspecting of your plants. Yes, quash ALL intruders and fumigate or spray if necessary, far better and so much easier to deal with an small outbreak now than having a damaging invasion on your hands in spring.
Also remove all diseased foliage at once to prevent botrytis developing.
Remember, prevention is better than a cure!