I'm having trouble differentiating between crown rot (Phytophthora) symptoms and rootstock infections with fire Blight (Erwinia). Any good diagnostics? Thanks
Howdy Hilary, I find with fireblight, the dead leaves of affected parts remain firmly attached. In spite our windy condition, sometime the dead leaves remained on the branch into spring. If the air is very humid, fireblight produces the amber ooze. Peace Thean
Fire blight; Erwinia amylovora is a bacterium that causes sudden brown to black leaves, which then wilt and die, they sometimes appear to be "burned". Affects Rosaceae family the most. A slight sunken encircling, with dark-brown to PURPLISH-black cankers with often a cracked margin form on twigs,branches and the trunk. Fruits are water-soaked, later becoming brown then black and shrivelled. In moist spring weather droplets of the bacterium ooze from the "holdover" cankers. The disease is spread intercellularly. And can move up to 4' through the vascular tissues in the late-spring to early-summer, darkening and killing the tissue. Rare on the Coast. Characteristic is that the blighted foliage remains on the tree after leaf-fall in the autumn. Cut effected parts back hard at least 35cm. And burn the affected debris. Insidious disease.
