The Leaves on a Transplanted Pear Tree Are Turning Dark

Fire Blight Disease

• Fire blight disease causes the leaves of transplanted pear trees to turn dark. The disease is caused by a bacteria and is among the most lethal pear disorders. The leaves, fruit, twigs and blossoms of the tree can all be affected as the leaves shrivel and wilt before turning black. The foliage does not fall from the specimen but instead remains hanging, giving the tree a burnt, scorched appearance and the origin of the name "fire blight".

Fire Blight Damage

• Whether the pear tree is transplanted or not, fire blight does most of its damage in humid conditions with temperatures exceeding 70 degrees Fahrenheit. The leaves of the tree often defoliate entirely, while cankers -- depressed, dark, sores -- develop on the limbs, twigs and trunk. An ooze of liquid bacteria seeps from the cankers. As the enlarge, the cankers may girdle -- strangle -- the branches and further deprive twigs and leaves of water and nutrition.

Fire Blight Management

• Fire blight bacteria overwinters on the tree and with the coming of spring is spread easily via insects, gardening devices and splashing rain. Infected sections of the pear tree should be cut out or pruned, with the litter destroyed and shears sanitized before working on another section of the tree. Chemical control, in the forms of sprays directed at the blossoms of the tree, are help to minimize the spread of fire blight disease.

Transplanting Stress

• Transplanting a pear tree places stress on the specimen and the roots may often be damaged to the point that it takes them considerable time to regrow and adapt to the new soil. Roots that are not working to their full capacity are unable to supply proper nutrition and water to the leaves, a deprivation that causes the foliage to turn dark -- typically brown -- and prematurely fall to the ground. Forunately, pears are adaptable to a soil pH level ranging from 5.0 to 7.5.