On which part of the plant does fireblight cause orange-red streaks?

Fireblight, caused by the bacterium Erwinia amylovora, primarily affects certain plants, particularly those in the Rosaceae family, such as apple and pear trees. One of the key symptoms of fireblight is the appearance of orange-red streaks, which are most commonly observed in the bark of infected branches.

This disease progresses through the plant, especially in young shoots and branches, leading to the characteristic cankers that develop in the bark. The orange-red streaks are indicative of the bacterial infection and are part of the plant's response to the disease. The discoloration occurs as the bacteria invade the vascular tissue, leading to necrosis and the release of pigments within the bark.

While the leaves and fruit can show symptoms of fireblight, such as wilting or darkening, it is specifically in the bark where the orange-red streaks are a prominent and identifiable characteristic. The roots are generally not visible and do not typically show such symptoms associated with fireblight. This makes bark the correct part of the plant where one would observe the distinct orange-red streaks associated with this pathogen.