MIMOSA WILT DISEASE
Mimosa vascular wilt can affect not only mimosa trees but also young seedlings of flowers and vegetables, sometimes even large vegetable plants while producing fruit. Still, we would like to concentrate on the couple of rather exotic trees which can be cultivated in Central Europe where they are hardy enough but may be prone to this disease in unsuitable soil conditions. Those are silk tree (albizia julibrissin) and cider gum (eucalyptus gunnii).
Watch for these symptoms:1. Young vegetable plants and flowers turn yellow, wilt, and quickly die. Often only a few among a large number, but sometimes also one by one until the whole bed is dead.
2. The same may occur to large vegetable plants in the middle of summer. Their dying takes a little longer but is imminent.
3. Woody plants (shrubs and trees) show yellow and drying leaves in the middle of the growing season, usually followed by complete defoliation branch by branch. Later the trunks show discoloration in enlarging areas and later on orange dots on dead wood.
How and where does this disease live?It loves constantly moist, compacted soils which seldom dry out. When it finds a host it searches for a wound on its roots or scars on the trunk or branches to invade it with its spores. Then it grows into the host’s tissue and begins to produce spores which flow along with the sap up the tree. They stick to the vessel edges and grow through their walls and into cells which results in limiting the sap flow up the tree whose canopy or top branches dry out in the absence of sap (water and nutrients). Also, the spores produce a sticky brown liquid protecting themselves from any optional fight back. It is clearly visible when you cut off a branch as a sticky brown circle around the woody centre. In every effort to survive the plant starts producing sprouts in its lower parts but they are short-lived and it is only a question of time when the bark is fully infested with the spores which block the sap flow throughout the tree. Depending on the tree age and strength the fight between the plant and the disease takes 6-24 months.
Prevention is bestHow many times have we heard that! But when we have a sick tree we don’t really seem to care less about prevention. Still, read this in case you are one of the lucky ones who is only about to plant his silk tree or cider gum. The most crucial thing is to make SURE your soil is FREE-DRAINING. If not forget about either of those species whatsoever. If your soil is fine and all water drains out, treat the planting spot and a bit around with a soil-fungi killer. Let it work for a few days and then water is exceedingly to make sure all debris of any possible diseases washes away before you put your tree in.
When your tree shows symptoms Many botanists and horticulturists believe than an infected tree will most surely die. But we have seen cases when some extra work helped the trees survive even if their canopies had to be chopped off and the tree turned to a multi-stemmed shrub. But alive. Still, giving this hope we must admit that many trees cannot be saved if you spot the disease too late or your growing conditions give way to the growth of the fungi rather than the tree. In any case, here is what to do if you want to save your tree:
1. Do the following AS SOON AS you spot the disease. 2. Treat your soil around the roots of your tree with a recommended soil-fungi killer.
3. Let it work for 3-4 days and then water the spot thoroughly.
Result A) If the water soaks in and drains quickly, all good and follow to 4.
Result B) If the water does not drain out and the soil remains wet or even muddy, give it up – your place is far from ideal for growing silk tree or cider gum. Dig out your ill tree and burn it to prevent the spores from spreading around your garden and the neighbourhood. I’m afraid we’re done here, no further reading necessary.
4. 1-2 days after you have heavily irrigated your tree use a balanced fertilizer 10:10:10 (N-P-K), never use any other ratio.
5. 3-4 days later water the place thoroughly again and 2 days later use fertilizer again. Keep repeating this routine until you see new sprouts up on the tree, not only in lower parts, and that any yellowing and wilting of leaves stopped.
6. If you save your tree, do one or two rounds of this routine every year in late spring as a prevention.
A wise man once said that impossible is made possible by those who had never been told that it had been impossible. 😊 I will keep my fingers crossed for you to save your beloved trees because both silk tree and cider gum are worth an extra effort as opposed to immediate cremation.
