So far as I am aware my Eucalyptus haven’t had any diseases. Any loses have ultimately been down to severe wind burn or lack of hydration in one particular area where there is also a lot of shading during the winter.
The only pest that I have had an issue with is blue gum psyllid.
I don’t spray with chemicals, and even during the second year I noticed a huge increase in the number of earwigs which to my surprise turned out to have a voracious appetite for the larvae of blue gum psyllid 😁
Parasitic wasp which was particularly effective in California and it was introduced to Ireland, though it doesn’t seem to be widespread as yet. They are tiny, so possible I do have them, but haven’t noticed.
Generally you would notice the wasp galls on the leaves rather than these tiny wasps.
Farm Forestry New Zealand don’t consider blue gum psyllid to be a serious issue, though I have noted they can have a detrimental effect on new tender foliage, especially the myrtle family of Eucalyptus where the juvenile leaves create an ideal sheltered habitat. I will continue with my control methods until the trees are too tall to reach affected areas, by which time I expect to have a predator balance and or the trees will have their adult foliage and will no longer be susceptible.
The Farm Forestry New Zealand article details that this pest excretes sticky honeydew and that sooty fungi develop on infested plants giving a blackened appearance on the affected areas, and this has been my experience.
Generally though I have found that they can simply be washed off the foliage, perhaps the blast from the spray damages their tiny wings (they are only a few millimetres long) and areas sprayed with the nozzle of the hose on mist jet remain clear for a while at least.
Very interesting to see the growth of trees in the video above in comparison to the same trees in the video below.
I can reach my entire mini forest and nursery stock with a long flexible hose. I also have a back pack style sprayer, though I found the pressure in it was insufficient to wash the Psyllid off. Perhaps the more agricultural amongst you who have larger forests will also have access to more capable pressure sprayers.
Have to say they aren’t the most attractive of bugs
Bear in mind these bugs are only perhaps 3mm long max.
A few close ups
Blue Gum Psyllid sucking the honeydew out of the tender stem with their proboscis. I would assume the patch of yellow at the bottom or the stem are the eggs
Sticky honeydew which they use for their egg nursery and which attracts sooty mould
These are the nymphs, the second stage of the blue gum psyllid life cycle. Eggs > Nymphs > Flies is my current understanding.
More information on the Psyllid can be found in the Teagasc report on the Eucalyptus leaf eating beetle