I've got young feijoas in my garden, and I'm in Wellington, NZ. I will have a look and see if there are signs of disease - if I have something similar then it might make it easier to identify. If it was a root problem, the plant would probably be wilting (despite having enough water). I think that this is probably a leaf fungus based on your description. It is quite likely that the plant had it when you got it, just not so obvious. It may be made worse by the plant being in a protected environment in the greenhouse, although the weather lately has been encouraging to fungal disease. Unless you see the black leaf spots obviously getting larger and joining up, it is probably something that the plant can live with. If it was a root problem, it would be worse. In general feijoas don't have too many problems, so I wouldn't be too concerned. If you can, get it outside so there is more air movement - hopefully not gale force winds though. While feijoas are considered wind-tolerant, they aren't "Wellington wind-tolerant". Try and protect it a bit, especially from the southerly, which is the more damaging wind to plants. Also, don't overwater - if the drainage is good and there isn't a saucer underneath, overwatering probably won't be an issue, just don't let the pot stand in water. Don't overfeed as that can make plants vulnerable to disease as well. While I'm greatful that Wellington doesn't have the temperature extremes of North America and Europe (and I'm especially grateful not to be in the snowstorms I've seen on TV lately), Wellington is having pretty extreme weather right now. My rain gauge recorded more than 80mm of rain over the weekend, with gale force winds and temperatures more typical of winter. Unfortunately, it's just a bad growing season for everything except fungi, and there is a lot more disease around. I've attached a link to my garden blog in case you are interested. It is largely just my personal record of what I plant and what I eat from the garden, but you might find something useful there. Here is a link that might be useful: Wellington edible garden blog

You can buy rolls of brown kraft paper made for wrapping trees. There are also white plastic spirals available for the same purpose. Thinned white latex paint also works to reflect winter sun. For the first two methods, it's best to wait until after several hard frosts before applying - this helps prevent any insect from taking up residence under the protective layer. The paint can be applied earlier or also just before deep cold sets in. Keep it out of the existing wound, though. Whatever method used, protect the bark from ground level to the lowest branches. It has traditionally been advised that the paper or plastic should be removed once the worst of cold weather is past, but many people don't. The paint washes off eventually by itself, but may be a bit unsightly until it does. You can also erect a burlap screen on the southwest side that doesn't actually touch the tree at all. For just a few trees, this method has much to recommend it - timing isn't an issue, won't hold moisture against the bark, once removed the bark is just as it was.

It is hard to tell you without pictures, since your trees have been outdoors. You should really try and see if they are mites. If those webs are from regular spiders, please, don't kill them:-) If you take a closeup of those webbs, someone like Rhizo well educated in that field could identify for you:-) Leaves will fall of green if you have underwatered it. Leaves fall off green, curled, and not flexible if they are infested with mites. Leaves will fall off green if the roots all of sudden just shut down. I would really make sure you have the right pest identified since it would not suprise me to see mites attck your tree in such a weakend state, nor would it suprise me to see a few regular spiders take up residence since some have in mine already. Regular spiders could of made an appearence on your tree since it has been outside looking for a hiding spot or food. Please make sure you do not have them confused. If you are 'certain' they are mites, then we can take it from there. Happy growing! Mike

I bonsai Plants, and currently have a Tangerine * and an Avocado no bigger then a small dog* in my care. My tengerine needs a good root pruning. Ya thats what I said a root pruning. As long as the Branches to not exceed more then half of the root ball, then your making a very healthy plant. This will back up any statement I plan on saying, Look up the art of the Bonsai. Which involves a lot of pruning roots and branches even citrus trees. In containers it is often that the soil gets compacted, this causes the little issue I am having, ware its winter and it needs it roots trimmed. * I hate using garbage bag in doors and it just gets messy* the act of simply loosening the soil, helps a lot, since containers do not have earth worms to keep it nice and airy. however in instances when in a pot, your roots tend to out grow the leafy part causing well the loss of leaves. Roots need energy to stay alive as well. If you have to much of a Leafy top to your tree, you loos leaves again, resulting in again your's and mines issue. However mine is simply due to it being that time for a root pruning, as my roots have out grown there leaf top. That and its pretty compacted in there..... I should probably changed the soil all together, but its winter ware I am at in winter potting soil is a rare find.