I have a number of eucalyptus seedling that are still quite small (from one to five centimeters). After bringing the ones I had outside during the summer back indoors most of them got a black fungus looking growth on their leaves and started dying. The growth starts at the growing tip and works its way down. In the end it kills all the leaves and just the tiny stem is left, which is still too small to produce new leaves.
At the around that time one of the pots of seedlings that I had kept indoors got the same black growth. It happened around the same time I brought the other seedlings in but the pots where never in the same room.
I think that the black growth is some kind of fungus and that its onset has something to do with the lower light levels present indoors. What confuses me is that it only seems to be effecting E. gunnii and some other mixed eucalyptus species that I sowed with them. The E. cinerea seedlings I have (I have a lot of Eucalyptus seedlings) are doing fine and I have not seen any black growth on them.
Has anybody experienced something similar? I am looking to grow more eucalyptus species from seed in the future but want to know if there's a way to prevent this before I do it. At this point it has killed all but a few of the biggest E. gunnii seedlings I have.
So far the only thing I can think to do different is plant them earlier in the season so that they can stay outside longer and get more woody by the time I have to bring them indoors. I have a year+ old eucalyptus tree right next to the ones effected by the black growth but it has not shown any signs of infection, so I am guessing it's only a problem for the seedlings.