Fungus induced acacia galls

Description:

Clusters of tough woody balls; each large cluster (containing about 8 spheres) coming from a single stem; younger ones very orange and crusty; older ones becoming progressively darker and harder ranging in colour from brick-red to almost black. Each ball approx. 20mm dia.

Habitat:

Clumping along the exposed roots of a fine leafed acacia in very wet conditions. One single specimen seen about 70cm up a young stem.

Notes:

These are fungus induced galls often called rust fungus. The progression of age may well represent yearly growths. The whole cluster can snap off revealing a single narrow stem. I have sliced one open and put it under a microscope in pics 4, 5 and 6. (300x, 400x and 600x) The body seems to be like grainy bread but there also appears to be occasional clear-white filaments inside. The sectioned one was an older dark version and although quite hard it has shrank much further over the last 3 months down to maybe half it's original size. This shrinkage would not be the case with the in-situ ones so it may be using host moisture. http://invasivespecies.org.au/traction/p... "Uromycladium tepperianum is a microcyclic rust that infects more than one hundred species of Acacia... and several other genera in the Fabaceae, causing large, conspicuous galls... Acacia pycnantha Benth., cultivated in Australia for its bark, is severely affected by U. tepperianum, which causes significant yield losses and eventually the death of the host ... However, this rust has potential as a biocontrol agent for weedy acacias outside of Australia, for example, U. tepperianum has been proven a highly effective against A. saligna in South Africa..." - US Department of Agriculture "Telia develop on galls on leaves, branches, inflorescences, and fruits; infections causing swollen, distorted galls up to 18 × 6 cm, and witches' brooms of different shapes and sizes, cinnamon to chocolate brown, powdery; teliospores composed of a cluster of three probasidial cells at top of a single pedicel, depressed globose to globose, cinnamon brown, thickly vertically striate, margin crenulate, wall 2-3 µm, at apex up to 5 µm thick, 14-22 µm high, 18-25 µm wide, one apical germ pore; pedicel hyaline, septate, deciduous. Hosts: Species of Acacia, Albizia and Racosperma (Fabaceae) Geographic Distribution Australia, Java, New Caledonia, New Zealand, Papua New Guinea, and South Africa. Uromycladium is characterized by the production of teliospores composed of 1-3 probasidial cells, with or without cysts, on a single pedicel. Eight species of Uromycladium have been described occurring primarily on Acacia in Australia and New Zealand. Teliospores of Uromycladium tepperianum and U. notabile McAlpine have three probasidial cells and no cysts (Burges 1934). Uromycladium notabile produces uredinia, and the probasidial cells have linear verrucae, while no uredinia are known for U. tepperianum and the probasidial cells are distinctly striate. Uromycladium acaciae (Cooke) P. Syd. & Syd. produces teliospores with two probasidial cells and no cysts. Teliospores of Uromycladium simplex McAlpine and Uromycladium robinsoni McAlpine have one globose probasidial cell and one cyst. Uromycladium fusisporum (Cooke & Massee) Savile has teliospores with one probasidial cells and no cyst (Savile 1971). Uromycladium maritimum McAlpine and Uromycladium alpinum McAlpine produce teliospores with two probasidial cells and one cyst." - US Department of Agriculture