If you notice that leaves on your apple tree have started to die and turn a rusty color, you may wonder if it has contracted a disease. If so, look for the following three signs that your tree is infected with the bacterial infection known as fire blight.
Base of Twigs Becomes Dry and Sunken
One symptom of fire blight can be found at the base of the infected twigs, a favorite entry point for the bacteria. Normally, when new branches grow out from older growth, the twig's surface is moist, smooth, and pliable.
However, when fire blight infects the tree, the base starts to take on a sunken appearance. You may also see cracks in the wood because the bacteria is robbing the twig of moisture, severely drying it out.
New Growth Dies and Bends Upward
As the disease progresses and moves towards the end of the new growth, the dried up twigs start to die. As they die, you will see it start to bend upward.
Eventually, the bending of the new growth will become so dramatic that it forms a hook. Once it reaches this stage, the twig is so dried up that it dies quickly. When examining the twigs, you will see what looks like a dried up shepherd's crook.
Dead Leaves and Apples Do Not Fall
When leaves and apples die on an apple tree, such as in autumn or from dry weather, they fall to the ground. This normally frees up any nutrients that the tree was attempting to use to feed the dead sprouts and fruit.
However, if your apple tree has fire blight, the dead growth remains on the branches. The bacteria then continue to feed on the water and nutrients meant to help the leaves and apples grow. If the dead leaves, apples, and branches are left on the tree, the bacterial infection will eventually spread. The tree will need to be pruned to remove the diseased and dead matter. However, do not attempt to do this yourself, as pruning the tree improperly could kill it. You need an arborist or other tree professional.
If you notice any of the above symptoms in your apple tree, it has likely contracted fire blight and should be examined by a professional so they can verify the diagnosis. Contact an arborist to have them diagnose the problem and prune the tree properly so that the fire blight infection does not spread throughout the tree and kill it.