Which pathogen is responsible for peach leaf curl?

Peach leaf curl is primarily caused by the fungal pathogen Taphrina sp., particularly Taphrina deformans. This pathogen specifically targets peach trees and leads to distinctive leaf symptoms such as curling, thickening, and discoloration of the leaves. The infection occurs when fungal spores invade the leaf tissue, disrupting normal growth and development.

Conditions that favor the establishment of Taphrina include cool and damp weather, especially in early spring, which is when the leaves are unfolding. The management of peach leaf curl typically involves cultural practices such as proper pruning, maintaining tree health, and applying fungicides during the appropriate times to prevent infection.

In contrast, other pathogens listed, such as Venturia, Fusarium, and Botrytis, are associated with different types of diseases on various hosts. Venturia species cause leaf spot diseases in other fruits, Fusarium is known for root and stem rot diseases, and Botrytis typically causes gray mold in flowers and fruits. These pathogens do not specifically target peach trees in the manner that Taphrina does. Therefore, Taphrina sp. is identified as the correct answer for the cause of peach leaf curl due to its direct association with the symptoms observed on the leaves of peach trees.