Apple trees can contract different infections, including insect infestations and fruit diseases. Apple tree bark is susceptible to disease as well and, if left untreated, it can affect the plant from its leaves all the way to the roots. Most apple tree bark diseases can be successfully treated if caught early.
Fireblight is an apple tree bark disease caused by bacteria (Erwinia amylovora). This infection gets its name from its burnt appearance which that first shows up on apple blossoms and moves its way to branches and twigs. Cankers or discoloured oozing patches form on the apple tree bark, specifically on the branches. Persistent fireblight infections can be fatal to an apple tree.
Apple scab diseases
Apple tree scab can cause severe damage if untreated. Scab is caused by the Venturia inaequalis fungus and results in deformations, cracks on the tree bark and entire tree death. Cankerous scab lesions can be seen on the apple tree bark, and wind and rain splashes can spread the fungus from infected tree parts.
Black rot disease
Black rot is known as frog-eye leaf spot and is caused by a fungus of the physalospora species. This disease appears as cankerous lesions on apple tree bark, and lesions can spread to cover an entire tree branch. Black rot causes rotting of apple fruit and can ruin an apple harvest if left untreated
Sooty blotch and fly speck
Sooty blotch and fly speck are two different apple tree diseases that can occur at the same time. Fly speck is caused by microthyriella rubi fungus, and gloeodes pomigena causes sooty blotch. Both diseases manifest and appear on the surface of the apple fruit. While the infection shows on the fruit only, the diseases infect the entire body of the apple tree, including bark on branches and twigs.
Flat-headed borer insects
The flat-headed apple borer is a member of the chrysobothris species of borer insects, which mostly affects newly planted apple trees, which are most susceptible. Flat-headed borers take away necessary nourishment from apple trees. Damage caused by these insects can result in dieback of apple tree twigs and branches or even killing off of the entire tree.
Apple tree diseases, and those that affect tree bark, can be treated with insecticide or fungicide.