Florida ranks among the most important citrus growing regions in the USA. The present study investigates the occurrence, diversity, and pathogenicity of fungal species associated with symptomatic sweet orange (Citrus sinensis) cv. Valencia plants and fruit. The survey was conducted on twigs and fruit collected in Southwest Florida during 2022. Based on morphological and molecular characteristics, the identified isolates belonged to the species Lasiodiplodia iraniensis, Diaporthe pseudomangiferae, and Diaporthe ueckerae. The pathogenicity of representative isolates was evaluated on citrus fruit and plants. Lasiodiplodia iraniensis was the most virulent on fruit and plants, followed by Diaporthe pseudomangiferae. Diaporthe ueckerae had the lowest virulence on fruit, and it was not pathogenic to plants. In vitro tests were performed to assess the effect of temperature on mycelial radial growth. The optimum temperature of growth ranged from 26.0 to 28.4 °C for all the evaluated species, and L. iraniensis showed the fastest mycelial growth. This study represents the first report of L. iraniensis as a causal agent of tree dieback and fruit stem-end rot on C. sinensis worldwide. Moreover, D. pseudomangiferae and D. ueckerae are reported here for the first time in association with citrus diseases worldwide.

Citrus fruit crops are important in many countries. Anthracnose, post bloom fruit drop, fruit stem-end rot, twig and branch dieback and gummosis, caused by Colletotrichum spp., are diseases that seriously threaten citrus production. Surveys of kumquat (Fortunella margarita) orchards were conducted in Eastern Sicily, Southern Italy, during 2022-23. Fungi isolated from twig and branch dieback of F. margarita were identified as Colletotrichum karsti through multi-locus (gapdh, tub2 and act) phylogeny. Pathogenicity and aggressiveness on detached apple fruit and kumquat plants were confirmed for a selection of representative isolates, although with different levels of disease incidence observed. This is the most comprehensive study on identification of C. karsti as the causal agent of twig and branch dieback of kumquat.

Citrus is one of the most economically important crops in Florida. In 2022 surveys of 46 citrus groves in southwest Florida, twig dieback and anthracnose on fruit, leaves and twigs were frequently observed. The occurrence, diversity, pathogenicity and sensitivity to chemical compounds of Colletotrichum strains isolated from symptomatic Citrus sinensis cv. Valencia were investigated. One hundred representative monoconidial isolates were identified as Colletotrichum gloeosporioides by phylogenetic analysis based on five genomic loci (GAPDH, ACT, TUB2, GS and ApMat). Fruit pathogenicity tests performed on seven representative isolates confirmed the pathogenicity of the identified species. This study is the first report of C. gloeosporioides associated with twig dieback and preharvest anthracnose on Ci. sinensis cv. Valencia in Florida. The sensitivity of 100 isolates of C. gloeosporioides to fenbuconazole (DMI), fluopyram (SDHI) and pyraclostrobin (QoI) was assessed by inhibition of conidial germination. Over 50% of tested isolates showed reduced sensitivity to fenbuconazole, fluopyram and pyraclostrobin, providing the first evaluation of the in vitro sensitivity of C. gloeosporioides strains isolated from Ci. sinensis cv. Valencia in Florida. These molecules appear unable to control the spread and development of C. gloeosporioides on Ci. sinensis cv. Valencia in Florida. Due to several citrus diseases that have severely affected Florida's citrus industry over the past 20 years, fungal diseases such as anthracnose have been neglected, but are increasing in importance in recent years worldwide. Our study represents a starting point for the development of new solutions to manage this problem for citrus growers.

‘Mal dello stacco’, a destructive fungal trunk disease of hazelnut, is caused by Anthostoma decipiens. This disease manifests as wedge-shaped cankers, vascular necroses, branch cracking, and reddish masses on bark surfaces. The disease has rapidly increased in incidence and spread, resulting in significant qualitative and quantitative yield reductions. Disease management strategies remain insufficient, without reliable tools for early pathogen detection in hazelnut nurseries or field plantations. This study developed and validated an SYBR Green quantitative real-time PCR (qPCR) assay for the detection and quantification of A. decipiens in hazelnut wood. Primers were designed on the nuclear ribosomal internal transcribed spacer (ITS) region. The assay was optimized and validated according to EPPO standard PM 7/98 (6), for analytical specificity and sensitivity, selectivity, repeatability, and reproducibility. The primer pair AD8_F/AD16_R successfully amplified a 154 bp fragment in all of 32 A. decipiens isolates, without amplification for 42 off-target species up to 35 cycles. The assay detected up to 100 fg of pathogen DNA in water and hazelnut DNA, with reaction efficiencies from 97% to 100%, and high reproducibility across operators and sessions. The assay was validated on artificially inoculated and naturally infected hazelnut plants from Italy, Spain, and Serbia, and from ten hazelnut cultivars. The qPCR assay developed is a reliable, rapid, and cost-effective diagnostic tool for early detection of A. decipiens, with potential applications in nursery certification, orchard monitoring and epidemiological studies.