Association of Paecilomyces cf. variotii with dieback of almond and peach trees in Chaharmahal va Bakhtiary Province

From 2019 to 2024, a study was conducted to identify the bacteria associated with canker symptoms and dieback of branches in stone fruit trees in Chaharmahal va Bakhtiary province. In some cases, a fungal species was isolated, which was notably prevalent, as it was found in about 11% of the samples (48 out of 436 samples). Out of these 48 samples, 36 were from almond trees and 12 were from peach trees. The symptoms in the infected trees appeared as gum secretion (often white) scattered on the branches and main trunk. A cross-section of the branch showed discoloration in the woody tissue, ultimately leading to the dieback of the shoot tips and the entire branch. The isolates exhibited rapid growth in PDA and nutrient agar media, producing a powdery, yellow-brown color. The morphological characteristics of the isolates matched those of Paecilomyces cf. variotii. The pathogenicity of the isolates on cut branches of almond and peach was confirmed under laboratory conditions. The frequency of isolation of this pathogen was higher on the sun-exposed side of trees and in orchards with poor nutrient and irrigation management. Isolation of this pathogen and the related symptoms were most noticeable in the summer of 2024. It seems that factors such as water stress, sunburn, and high temperatures may predispose trees to diseases caused by this pathogen in almonds and other stone fruit trees. This is the first report of the isolation of P. cf. variotii association with dieback symptoms in stone fruit trees in Iran.