Sunday, May 20, 2012
Have you noticed that pear trees (ornamental and fruit-producing) look pretty bad this season? If not, take a look when you are around and about and you may notice lots of blackened areas on the trees (the fruits-yes, even ornamental Bradford pears produce little fruits) might be blackened and shriveled and the new growth leaves likewise. This is probably fire blight, and we have been having a hard time of it this season. There has always been a little of this bacterial disease in my yard- my apple tree gets a bit, but is mostly sturdy and resistant. This year I first noted it on my fire-blight resistant Moonglow and Magness pear trees. Last season Magness had it, almost enough the kill the tree completely, but seems OK this season. This year, however, the Moonglow is more affected.
Fire flight is caused by a nasty bacteria that can kill a tree, if the bacterial disease spreads to the root zone (and it probably will, especially on a small tree, if you take no action). The first defense is the plant fire-blight resistant varieties, but as my experience has shown, these are resistant to the bacteria, not immune to it. Next, to keep your tree as healthy as possible, plant it away from other susceptible host plants, like many apple varieties (oops, I messed up there- my pears are too close to my apple tree!). Use compost as a fertilizer to insure steady, not explosive, growth. When you first see the signs of fire blight (leaves or stems that turn black) you need to out race the disease by selective pruning. Cut the branch below the infected area (you will see where the stem turns black, and cut several inches below that). Spraying an infected tree with an antibiotic spray or, early in the growing season, an organic, copper-based spray will also limit the disease. The copper spray is necessary to suppress the cankers which overwinter all over the tree bark, and which spread the disease in spring.
The photo above shows three cuttings from my pear tree to help identify fire blight. Look carefully at the cutting on the left. See the sprout of leaves at the top and how that twig is black? Then how the branch near to it is black too? That is fire blight. The cutting in the middle seems healthy, green leaves and brown bark. The right most cutting has a black stem and one dead, shriveled shoot on the bottom right. Though the leaves look good, this twig was destined to die, as it is infected with fire blight. If you see new growth that is all black, leaves and stem, sometimes curled in a shepherd's crook shape, that is fire blight too.
Hope you are avoiding the blight and have a happy garden!