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We present relative astrometric and photometric measurements of visual double stars made in 2013–2015, with PISCO2 installed at the 76‐cm refractor of Côte d'Azur Observatory in Nice (France). Our observing list contains orbital couples as well as double stars whose motion is still uncertain. Most of the observations were done in 2015, but some other observations of wide couples were done in 2013–2014 (0.3% of the total of the observations). Three different techniques were used for obtaining measurements: lucky imaging, speckle interferometry and the direct vector autocorrelation method. From our observations of 2837 multiple stars, we obtained 5182 new measurements with angular separations in the range of 0″$$ {}^{{\prime\prime} } $$.1–32″$$ {}^{{\prime\prime} } $$ and an average accuracy of 0″.018$$ {0}^{{\prime\prime} }.018 $$. The mean error on the position angles is 0°.8. Most of the position angles were determined without the usual 180° ambiguity with the application of the direct vector autocorrelation technique and/or by inspection of the Lucky images or the long integration files. We managed to routinely monitor faint systems (mV≈9−11$$ {m}_V\approx 9-11 $$) with large magnitude difference (up to ΔmV≈4.5$$ \Delta {m}_V\approx 4.5 $$). We have thus been able to measure 21 systems containing red dwarf stars that had been poorly monitored since their discovery, from which we estimated the stellar masses thanks to Gaia measurements. We also measured the magnitude difference of the two components of 1079 double stars with an estimated error of 0.2 mag. Except for a few objects that are discussed, our measurements are in good agreement with the ephemerides computed with published orbital elements, even for the double stars whose separation is smaller than the diffraction limit. Thanks to good seeing images and with the use of high‐contrast numerical filters, we have also been able to obtain 196 measurements with an angular separation smaller than the diffraction limit of our instrumentation, and consistent with those obtained with larger telescopes. We also report measurements of the 164 new double stars that we found in the files obtained during the observations. Finally, from a study of the DR3 Gaia release, it is shown that all the objects of the Tycho Double Star Catalog that we did not resolve in 2015 are probably false detections by Tycho. [ABSTRACT FROM AUTHOR]

We present new speckle measurements of the position of Linus, the satellite of the asteroid (22) Kalliope, obtained at the 1 m Centre Pédagogique Planètes et Univers -Epsilon telescope on the Plateau de Calern , France. Observations were made in the visible domain with the speckle camera Pupil Interferometry Speckle camera and COronagraph. We obtained 122 measurements in February–March 2022 and April 2023, with a mean uncertainty close to 10 milliarcsec on the angular separation. [ABSTRACT FROM AUTHOR]

Litchi (Litchi chinensis) pepper spot disease results in black spotting symptoms on litchi fruits. This disease was first observed on litchi cultivar Guiwei, in Guangzhou, China, in 2009, and then found widespread in other litchi‐growing regions of China. Colletotrichum isolates were consistently recovered from typical black spot lesions of diseased fruits with frequency ranging from 83% to 100%. Three representative Colletotrichum isolates from Maoming, Guangzhou and Shenzhen were selected for identification and pathogenicity testing in the field. Based on morphology and phylogenetic analysis using the ribosomal internal transcribed spacer region (ITS), glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH), calmodulin (CAL), actin (ACT), β‐tubulin (TUB2) and glutamine synthetase (GS) gene sequences, the three isolates were identified as C. siamense. In the pathogenicity experiments, typical symptoms appeared on the inoculated litchi fruits, including black spots and green patches around these black spots. These symptoms were consistent with the symptoms originally observed in the field. Colletotrichum siamense was successfully reisolated from the typical black spot lesions of the inoculated litchi fruits. To the authors' knowledge, this is the first report on characterization of C. siamense as the causal agent of litchi pepper spot disease in mainland China by successful inoculation on fruits under field conditions. [ABSTRACT FROM AUTHOR]

Citrus reticulata Blanco cv. Nian Ju, an important ornamental plant, is traditionally displayed during the Chinese Spring Festival because its golden fruits are a symbol of auspiciousness. In the spring of 2012, foliar blight was observed on 10 to 30% of the Nian Ju plants at four nurseries in Yangjiang, Guangdong Province, China. Initial symptoms appeared as brown to black foliar lesions, followed by expansion of spots into blight. Some young branches also had necrosis. During frequent rainfall and prolonged wet periods at 22°C to 30°C, white and dense mycelia and sporangia were observed on the infected seedlings. To isolate the causal organism, leaves and stems were cut into sections. Each section included some partial lesion and adjacent asymptomatic tissues. They were surface-disinfested in 1% sodium hypochlorite for 60 s, rinsed three times with sterile water, and placed on V8 juice agar (V8A) at 25°C. After 3 days, 10 isolates were obtained and purified by single-zoospore method. These isolates were identified to species level by sequencing the rRNA internal transcribed spacer (ITS) region. Four representative isolates had an identical ITS sequence (GenBank Accession No. KF750568), which had 99% homology with Phytophthora capsici sequences in GenBank. In addition, all recovered isolates were identical in morphological characteristics. They produced caducous, papillate, and ovoid to ellipsoid sporangia (Length × width = 46.2 ± 7.7 × 23.6 ± 11.3 μm), often with a tapered base. The average length of pedicels was 33.3 ± 4.5 μm. All isolates are A2 mating type. They produced gametangia when paired with an A1 tester of P. capsici isolated from pepper on V8A. Plerotic oospores were 25.3 ± 2.1 μm in diameter. Amphigynous antheridia were 13.6 ± 2.8 μm long and 11.2 ± 0.9 μm wide. Oogonia were 27.4 ± 3.2 μm in diameter. To determine the pathogenicity, three 3-year-old potted C. reticulata cv. Nian Ju plants were sprayed with 20 ml of zoospore suspension from one representative isolate at 10 5 per ml. Two control plants were sprayed with 20 ml distilled water. All plants were then maintained at 90% relative humidity at 25°C with a 12-h photoperiod. Symptoms similar to those observed in the nurseries developed on all inoculated plants but not on any control plants after 10 days. The pathogenicity test was repeated once and similar results were obtained. P. capsici was recovered from all inoculated plants and resultant isolates had identical morphology to that of the isolates used for inoculation. P. capsici has a relatively broad host range including pumpkins, cucumbers, peppers, beans, squashes, and spinach (1,2). To our knowledge, this is the first report of foliar blight of C. reticulata cv. Nian Ju caused by P. capsici. This study indicates that P. capsici is potentially an important pathogen of C. reticulata cv. Nian Ju plants and further investigations into its epidemiology and development of site-specific integrated management programs for this new disease are warranted. References: (1) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. American Phytopathological Society, St. Paul, MN, 1996. (2) D. Tian and M. Babadoost. Plant Dis. 88:485. 2004.

In the spring of 2011, leaf and fruit spot symptoms were observed in three orchards planted with Citrus reticulata Blanco cv. Nian Ju in Longmen City, Guangdong Province. The incidence of fruit and leaf spot ranged from of 5 to 25% across all three orchards. Similar symptoms were not observed on the fruit of C. reticulata cv. Shiyue Ju planted at the same orchards. Lesions on the diseased leaves and fruit first emerged on the lower portions of the trees and were initially small, circular, and diffuse in distribution over the leaf surface. Within 2 weeks, the small circular spots on the leaves and fruit enlarged to brown sunken necrotic lesions ranging from 5 to 30 mm in diameter. To isolate the causal organism, symptomatic leaves and fruit peels (from different trees) adjacent to the lesions as well as the lesions themselves were surface-disinfested with 1% sodium hypochlorite for 1 min and rinsed three times with sterile water. The tissues were then plated on potato dextrose agar (PDA) under alternating light and dark conditions at 28°C for 4 days. Sixteen fungal isolates with nearly identical fungal colonies were recovered from all samples. After 7 days of incubation, isolates with grayish white to dark gray mycelium and salmon pink conidia masses were observed. The conidia were hyaline, smooth-walled, aseptate, one-celled, and falcate, with oil droplets in the cytoplasm. The conidia were 19.7 to 22.5 (mean = 21.5) × 2.8 to 3.9 (mean = 3.4) μm. The fungal colonies also produced acervuli, setae, and sclerotia in the culture. The cultural and morphological characteristics of these isolates were consistent with the description of Colletotrichum truncatum (2). The ACT, TUB2, CHS I, GAPDH, and ITS regions of four representative isolates (GenBank Accession Nos. KF591214, KF591213, KF591211, KF591212, and KF011205) were sequenced and identical to those of the type specimen of C. truncatum CBS 151.35. To determine pathogenicity, leaves of three 3-year-old potted plants and ten 8-month-old fruit of C. reticulata Blanco cv. Nian Ju were each wound-inoculated with 20 μl of a suspension of conidia (1 × 10 5 conidia/ml). Leaves of an additional two potted plants and 10 similarly-aged fruit were wound-inoculated with 20 μl of sterile water as control. The citrus plants and fruit were then maintained at 90% relative humidity at 28°C with a 12-h photoperiod. Symptoms identical to those observed in the orchards in Longmen City developed on all of the inoculated citrus leaves and fruit after 14 days. The controls remained healthy throughout this period. The inoculation experiment was performed a second time with identical results. Isolates of C. truncatum identical to that of the isolate used for inoculation were obtained from all the inoculated symptomatic citrus leaves and fruit. C. truncatum has a broad host range and is known to be pathogenic on several crops including Medicago sativa L., Phaseolus lunatus, and Arachis hypogea (1,2,3,4). To our knowledge, this is the first report of leaf and fruit rot of C. reticulata Blanco cv. Nian Ju caused by C. truncatum in China. The golden-yellow fruit of C. reticulata Blanco cv. Nian Ju are commonly displayed during the Spring Festival of the Chinese New Year, and future epidemics of fruit spot may affect sustainability of this important cultural practice. References: (1) P. A. Backman et al. Plant Dis. 66:1032, 1982. (2) U. Damm et al. Fungal Divers. 39:45, 2009. (3) C. Eken and E. Demirci. Plant Dis. 84:100, 2000. (4) F. Huang et al. Fungal Divers. 61:61, 2013.

Citrus reticulata Blanco cv. Shiyue Ju, which produces one of China's most popular tropical fruits, is widely planted throughout southern China. In 2008, a new citrus disease was found in Zhaoqing City in Guangdong Province on about 20,000 ha. Yield losses averaged 15% on a wide range of different aged trees of C. reticulata cv. Shiyue Ju. No yield losses were observed on C. reticulata cv. Gong gan. Symptoms first appeared on young leaves as leaf lesions, which were reddish-brown, elliptical, and 2 to 5 mm in diameter. After several weeks, 20 to 70% of leaves dropped and 10 to 50% of fruits on the trees showed brown spots (5 to 40 mm in diameter). Leaves and fruit peels adjacent to and including lesions from different trees were surface disinfested with 1% sodium hypochlorite for 1 min and rinsed three times in sterile water. Then the tissues were plated on potato dextrose agar (PDA) in alternating light and dark at 28°C for 3 days. Twenty-three similar isolates of a fast-growing fungus were recovered from all samples. For identification, single-spore cultures were grown on potato dextrose agar (PDA) at 28°C. Initially, the colonies were white, but after 5 days, they became pale gray with concentric zones and greenish black beneath. No setae, acervuli, or ascocarp were observed in the PDA culture. Conidia formed in pink conidial masses, were hyaline, fusiform, straight, obtuse at the ends, sometimes slightly curved, and 14 to 20 × 4.5 to 6 μm (x¯ = 16.2 ± 1.5 × 4.9 ± 0.5, n = 100). The cultural and morphological characteristics of these isolates matched the description of Colletotrichum siamense (3), but not that of C. gloeosporioides or C. acutatum, which cause anthracnose on citrus plants (1,2). The actin, β-tubulin, CHS I, CAL, GPDH, and ITS regions of four representative isolates (GenBank KC524462, KC524463, KC524464, KC524465, KC524466, and KC524467) were identical and with almost 100% identity to those of the type specimen of C. hymenocallidis isolate CSSN3 (C. hymenocallidis is synonymous with C. siamense) (4), except for two inconsistent nucleotide bases in the GPDH gene. Four potted plants of C. reticulata cv. Shiyue Ju were used for pathogenicity tests. On each plant, 10 randomly selected leaves and four 6-month-old fruits were wound-inoculated with 20 μl of sterile water or conidial suspensions (1 × 10 5 conidia per ml). Plants were then maintained at 90% relative humidity with a 12-h photoperiod at 28°C. Symptoms resembling those in the field were observed on three inoculated plants after 14 days. In another similar experiment without wounding, three of 20 inoculated plants exhibited the symptoms after 14 days. Controls remained healthy throughout this period. The tests were performed three times. C. siamense was reisolated from all diseased inoculated plants, and the culture and fungus characteristics were the same as the original isolate. Thus, C. siamense was determined to be the pathogen causing leaf drop and fruit spot on C. reticulata cv. Shiyue Ju. To our knowledge, this is the first report of leaf drop and fruit spot on C. reticulata cv. Shiyue Ju caused by C. siamense. References: (1) H. Benyahia et al. Plant Pathol. 52:798, 2003. (2) N. A. Peres et al. Plant Dis. 89:784, 2005. (3) H. Prihastuti, et al. Fungal Diversity 39:89, 2009. (4) B. Weir et al. Stud Mycol. 73:115, 2012.