Occurrence and management of the emerging pathogen Epicoccum sorghinum.

Epicoccum sorghinum is a notorious fungal pathogen that causes leaf spot symptoms on a wide range of plants, leading to devastating losses in crop production and quality. Here, all reports regarding the occurrence and management of E. sorghinum are covered for the first time. E. sorghinum has been detected in tropical and subtropical climate areas during the rainy season, mainly from March to August, since 2016. Although E. sorghinum shows broad host spectrum, the disease incidence is especially notorious in cereal crops and ornamental plants, suggesting that these plants are especially susceptible. Control methods based on synthetic fungicides, plant extracts, and microbial biocontrol agents have been reported. However, most agents were applied using only in vitro conditions, restricting the information about their actual applicability in field conditions. Additionally, E. sorghinum can colonize cereal grains and synthesize the carcinogenic mycotoxin tenuazonic acid, posing an enormous hazard for human health. Furthermore, although E. sorghinum is an emerging pathogen that is currently causing yield penalties in important crops, there is lack of information about its pathogenic mechanisms and virulence factors, and there is currently no commercial antifungal agent to manage E. sorghinum. Collectively, it is imperative to conduct in vivo studies to determine the efficacy of antifungal agents and the most effective methods of application in order to develop suitable management strategies against E. sorghinum.

Pseudomonas chlororaphis metabolites reduce MfCYP51 expression and yield synergistic efficacy in mixture with reduced rates of propiconazole against DMI-resistant Monilinia fructicola isolates.

Brown rot caused by Monilinia fructicola is one of the most important diseases affecting peach production in the southeastern USA. Management often involves the use of demethylation inhibitor (DMI) fungicides, but efficacy can be compromised due to overexpression of the MfCYP51 gene encoding the 14α-demethylase of the ergosterol biosynthesis pathway. This study aimed to investigate the influence of the biorational fungicide Howler EVO containing Pseudomonas chlororaphis ASF009 metabolites, on the expression of MfCYP51 in M. fructicola and associated synergy with a DMI fungicide for control of DMI-resistant strains. Mycelia from two DMI-sensitive and three DMI-resistant M. fructicola isolates were exposed or not to propiconazole (0.3 µg/ml), Howler (78.5 µg/ml), or the combination propiconazole + Howler for 6 h prior to RNA extraction. Real-time PCR indicated that Howler reduced the constitutive expression of MfCYP51 in DMI sensitive and two of three DMI-resistant isolates. Propiconazole-induced expression of the DMI target gene was significantly reduced by Howler and by the mixture of Howler plus propiconazole in all isolates. Detached fruit studies on apple revealed that the combination of Howler plus a reduced label rate of Mentor (50 µg/ml propiconazole) was synergistic against brown rot caused by a DMI-resistant isolate in high and low inoculum spore concentration experiments (synergy values of 40.1 and 4.9, respectively). We hypothesize that the synergistic effects against M. fructicola resistant to DMI fungicides based on MfCYP51 gene overexpression can be attributed to reduced 14α demethylase production due to transcription inhibition, which may necessitate fewer DMI fungicide molecules to arrest fungal growth. The use of Howler /DMI mixtures for brown rot control warrants further investigation because such mixtures could potentially allow for reduced DMI fungicide use rates in the field without compromising yield or increased resistance selection.

Evaluation of Compost and Manure Amendments for Suppressing Heterodera glycines Ichinohe, 1952.

Soybean cyst nematode is a major pest of soybean crops, causing significant yield losses and economic impact. Current management strategies primarily rely on resistant varieties, cover crops, and seed treatments. However, there is a growing interest in developing sustainable, ecologically based approaches to integrate SCN risk reduction into soybean production systems. This study aimed to evaluate the efficacy of various compost and manure amendments in suppressing SCN populations and promoting soybean productivity. An in vitro egg hatching assay was conducted to screen the inhibitory effects of different compost and manure extracts on SCN egg hatching. Results indicated that poultry manure, Layer Ash Blend®, and swine manure extracts significantly inhibited SCN hatching compared to other treatments across multiple time points. Greenhouse trials further validated the effectiveness of Layer Manure®, poultry manure, High Carbon Dairy Doo®, and Seed Starter 101® in suppressing SCN cysts, eggs, and juveniles. A field microplot trial confirmed the practical promise of Layer Ash Blend® and poultry manure in SCN management, with significant reductions in SCN populations and increased soybean yields. The study also investigated the impact of these amendments on promoting the population of bacterivorous and frugivorous nematodes, contributing to a biological diverse soil ecosystem. Overall, the results indicate that amending SCN-infested soil with specific compost or manure formulations can effectively suppress nematode populations while improving soybean productivity. These findings contribute to the development of sustainable strategies for SCN management in soybean production systems.

Mechanical leaf removal for improved Botrytis bunch rot control in Vitis vinifera 'Pinot gris' and 'Pinot noir' grapevines in the northeastern U.S.

Late-season bunch rot can cause substantial yield loss in grapevines grown in humid regions. Fruit zone leaf removal has been widely used to reduce bunch rot and pesticide applications through improvements in canopy microclimate and grape cluster morphology. In this study, we evaluated if mechanical leaf removal can be a valid alternative to a labor-intensive manual application by comparing pre-bloom manual (PB-MA) and mechanical (PB-ME) leaf removal. We also evaluated the effects of the timing of mechanical application, pre-bloom (PB-ME) versus fruit set (FS-ME), on fruit traits and bunch rot, caused by Botrytis cinerea. Our trials were conducted on two Vitis vinifera 'Pinot noir' and 'Pinot gris' vineyards in the northeastern US over two seasons (2017-2018). Major findings were overall consistent between cultivars and years. Leaf removal provided reductions in fruit-zone canopy density regardless of method or timing. In general, PB-ME provided similar shifts in cluster morphological traits to PB-MA, including lower number of berries per cluster, cluster compactness, and cluster weight compared to control (no leaf removal) vines. At harvest, both pre-bloom leaf removal methods equally reduced Botrytis bunch rot severity, while Botrytis bunch rot incidence in Pinot noir was lowest for PB-ME in one year and PB-MA in the next year. When comparing timing of mechanical leaf removal, FS-ME provided Botrytis bunch rot reductions similar to PB-ME, without effects on cluster weight. Thus, under our growing conditions, FS-ME was considered the best mechanical leaf removal option to help manage Botrytis bunch rot without causing undesirable yield reductions.

Biocontrol potential of Cladosporium sphaerospermum against the wheat powdery mildew fungus Blumeria graminis f. sp. tritici.

Cladosporium spp. are known to be mycoparasites and inhibit phytopathogenic fungi. However, so far, little information is available on the impacts of Cladosporium spp. on powdery mildews. Based on the morphological characteristics and molecular analysis, C. sphaerospermum was identified as a mycoparasite on the wheat powdery mildew fungus (Blumeria graminis f. sp. tritici, Bgt, recently named as B. graminis s. str.). C. sphaerospermum was capable of preventing colony formation and conidial distribution of Bgt. The biomasses of Bgt notably decreased by 1.3, 2.2, 3.6 and 3.8 times at 2 dpi, 4 dpi, 6 dpi and 8 dpi, respectively. In addition, biomasses of C. sphaerospermum at 2 dpi, 4 dpi, 6 dpi and 8 dpi significantly increased to 5.6, 13.9, 18.2 and 67.3 times, respectively. In vitro, C. sphaerospermum exudates significantly impaired appressorial formation of Bgt. Thus, C. sphaerospermum acts as a potential biological control agent by suppressing the formation, distribution and development of Bgt conidia and is a viable alternative for managing the wheat powdery mildew. These results suggest that C. sphaerospermum is an antagonistic parasite of the wheat powdery mildew fungus, and hence, provide new knowledge about the biological control of phytopathogenic fungi.

Biological Control of Rapeseed Clubroot (Plasmodiophora brassicae) Using the Endophytic Fungus Didymella macrostoma P2.

Didymella macrostoma P2 was isolated from rapeseed (Brassica napus), and it is an endophyte of rapeseed and an antagonist of three rapeseed pathogens, Botrytis cinerea, Leptosphaeria biglobosa, and Sclerotinia sclerotiorum. However, whether P2 has a suppressive effect on infection of rapeseed by the clubroot pathogen Plasmodiophora brassicae remains unknown. This study was conducted to detect production of antimicrobials by P2 and to determine the efficacy of the antimicrobials and P2 pycnidiospores in suppression of rapeseed clubroot. The results showed that cultural filtrates (CFs) of P2 in potato dextrose broth and the substances in pycnidiospore mucilages exuded from P2 pycnidia were inhibitory to P. brassicae. In the indoor experiment, seeds of the susceptible rapeseed cultivar Zhongshuang No. 9 treated with P2 CF and the P2 pycnidiospore suspension (P2 SS, 1 × 107 spores/ml) reduced clubroot severity by 31 to 70% on the 30-day-old seedlings compared with the control (seeds treated with water). P2 was reisolated from the roots of the seedlings in the treatment of P2 SS; the average isolation frequency in the healthy roots (26%) was much higher than that (5%) in the diseased roots. In the field experiment, seeds of another susceptible rapeseed cultivar, Huayouza 50 (HYZ50), treated with P2 CF, P2 CE (chloroform extract of P2 CF, 30 µg/ml), and P2 SS reduced clubroot severity by 29 to 48% on 60-day-old seedlings and by 28 to 59% on adult plants (220 days old) compared with the control treatment. The three P2 treatments on HYZ50 produced significantly (P < 0.05) higher seed yield than the control treatment on this rapeseed cultivar, and they even generated seed yield similar to that produced by the resistant rapeseed cultivar Shengguang 165R in one of the two seasons. These results suggest that D. macrostoma P2 is an effective biocontrol agent against rapeseed clubroot.

First Report of Aspergillus niger causing rot of Morchella sextelata in China.

As an important edible mushroom, morel mushroom (Morchella spp.) has been widely spread and cultivated in China. However, between 2022 and 2023, a rot disease with a natural incidence of 28% occurred in morel mushroom farms in the Qingpu district of Shanghai (N30°97', E121°06'), China. High temperatures (>20℃) and high humidity (>70%) provide conditions conducive to the spread of this disease. First, a small white mold-like symptoms appeared on the surface or the pinnacle of pileus. The tissues in the infected parts stop growing and developing.Then the lesion developed to encircle the pileus and spread gradually to the stipe, seriously affecting its yield and quality. The infected tissue of morel fruiting body at the edge of the lesions was isolated and cultivated on potato dextrose agar (PDA) at 28℃ in the dark. After 3 days, monospore cultures formed black cottony colonies. In order to reliably identify, isolates were transferred to Czapek Yeast Autolysate agar (CYA) (Samson et al, 2014). On CYA fungal colonies consisted of a white mycelium, covered by a layer of black conidiophores. Scanning electron microscope analysis revealed that mature mycelia produced conidiophores ended with numerous metula and phialides. The phialides showed the number of conidia bearing rounded spores, which coincides with previous research(Silva et al, 2020). To confirm the identity of the pathogen, the genomic fragments for the internal transcribed spacer (ITS), beta-microtubulin (BenA), calmodulin (CaM), and RNA polymerase II second largest subunit (RPB2) gene of the isolate were amplified by PCR (White et al. 1990; Glass et al. 1995; Hong et al. 2005; Liu et al. 1999). The resulting sequence was deposited in GenBank with accession OQ931346.1, OR393310, OR393311, and OR393312, respectively. PCR results and morphological observations indicated the isolated strain was a pure culture and the strain was designated as MOR02. Comparison results indicated that the sequences with accession numbers KF305756.1, MK450794.1, HQ285594.1, and HQ285594.1 have high identity with the molecular sequences of A. niger MOR02, which is 99%, 98%, 98%, 99%, respectively. Phylogenetic analysis with ITS and RBP2 genes of the isolated strain and 9 Aapergillus spp. strains were performed using MEGAX software with Neighbor-Joining (NJ) method. Based on the results of growth habits, morphological observations, and phylogenetic analysis, the pathogen was identified as A. niger. A spore suspension of the A. niger strain MOR02 (1 x107 conidia/mL) was inoculated back to healthy morel mushrooms. Five healthy fruit bodies of M. sextelata were injected, and another five healthy morels were treated with potato dextrose broth（PDB） medium as controls. Morels were incubated for 7 days at 20℃ and 85% to 90% relative humidity. The pathogen successfully infected the morel showing a similar white mold-like lesion as the natural occurrence disease. The controls remained healthy without any symptoms. The pathogen was reisolated from the affected lesions and identified as A. niger MOR02 based on its morphological characteristics and phylogenetic marker genes. To our knowledge, this is the first report of A. niger causing rot disease of M. sextelata. This study confirms that A. niger is the pathogenic fungus causing morel rot on the Qingpu farm in Shanghai. The disease occurs under conditions of high humidity and high-temperature conditions. Better production management is the most important to prevent the disease.

Survival of Sclerotinia sclerotiorum Sclerotia in Central New York.

White mold caused by Sclerotinia sclerotiorum is a serious disease affecting many field and specialty crops in New York (NY). The primary inoculum for white mold is sclerotia that are hardened masses of mycelia that survive adverse environmental conditions and periods of non-hosts. However, NY crop guidelines lack rotation and residue management recommendations based on local knowledge of sclerotial survival. A field trial was established in October 2020 by deploying S. sclerotiorum sclerotia in mesh bags on the soil surface or shallowly buried (placed at 3 cm depth in the soil) at Geneva, NY. Bags were periodically collected from 67 to 769 days. At each time, sclerotial retrieval (number of sclerotia) was assessed by counted and viability evaluated through myceliogenic germination. Sclerotial retrieval was significantly affected by soil depth and was higher in those on the surface than buried. Time also affected the retrieval of sclerotia which was significantly reduced after 250 days. The interaction between burial and time had a significant effect on sclerotial viability. Approximately 15% of sclerotia placed on the surface were still viable after 769 days. After 433 days, viability of buried sclerotia was also significantly reduced compared to those on the surface. After 670 days, none of the buried sclerotia were viable. These findings suggest a rotation of at least two years between susceptible crops is required to reduce primary inoculum. However, given that low inoculum densities are sufficient to initiate a white mold outbreak, a longer rotation may be beneficial. In a cultivated system, timely tillage of crop residue to bury sclerotia after harvest to promote degradation is encouraged.

First report of Leaf Blight of Liquidambar formosana Hance caused by Alternaria tenuissima in China.

Liquidambar formosana Hance is widely planted in urban landscapes in China owing to its ornamental red leaves. In June 2020, a distinctive leaf spot disease was observed on L. formosana in Nanjing Forestry University, Jiangsu Province of China (32°4'49"N, 118°48'56"E). Approximately 61% (14 out of 23) of the trees displayed leaf spots. The diseased symptoms included irregularly distributed spots that showed black or dark brown, and occasionally with pale green halo. Two representative trees were selected for sampling and five leaves with typical symptoms were selected randomly for isolation. The tissues from the margin of the lesions (0.2 cm × 0.2 cm) were cut and disinfected in 1% sodium hypochlorite for 90 s, rinsed in sterile water twice for 30 s, and dried with sterile paper. Then, 20 tissues were incubated on 2% potato dextrose agar (PDA) supplemented with 100 mg/L Ampicillin Sodium and incubated in the dark at 25℃ for 4 days. Seventeen single-spore fungi were isolated from lesion tissues as described by Woudenberg et al. (2013). The colony morphology of 17 isolates was extremely similar, so 3 isolates (NFUA01, NFUA02, and NFUA03) were selected randomly for further study. Colonies on PDA were circular, gray, and slightly raised loose cotton mycelium, while the reverse side was olive green in the center with white margins. Conidiophores were brown, simple or branched, and produced numerous conidia in short chains. Conidia were obclavate or ellipsoid, brown, with 1-5 transverse septa and 0-3 longitudinal septa, and measured 7.1 to 32.5 × 3.3 to 13.3 µm (n=50). The morphological observations were consistent with the description of the genus Alternaria sp. (Woudenberg et al. 2013). Six gene fragments, including SSU, LSU, ITS, GAPDH, RPB2 and EF-1 region, were amplified and sequenced. The primers of six nuclear loci were used by NS1 / NS4((White et al. 1990), LSU1Fd (Crous et al. 2009)/ LR5 (Vilgalys & Hester 1990), V9G (De Hoog & Gerrits van den Ende 1998)/ ITS4 (White et al. 1990), gpd1 / gpd2 (Berbee et al. 1999), RPB2-5F2 / fRPB2-7cR (Liu et al. 1999), and EF1-728F / EF1-986R (Carbone & Kohn 1999). The sequences were submitted in GenBank (SSU, ON237470 to ON237472; LSU, ON237464 to ON237466; ITS, ON197354 to ON197356; GAPDH, ON237476 to ON237478; RPB2, ON237467 to ON237469; EF-1, ON237473 to ON237475). BLAST result showed that SSU, LSU, ITS, GAPDH, RPB2, and EF-1 sequences of NFUA01, NFUA02, and NFUA03 were identical to A. tenuissima at a high level (>99%, Table 1). A maximum likelihood and Bayesian posterior probability analysis were performed by IQtree v. 1.6.8 and Mr. Bayes v. 3.2.6 with the concatenated sequences (Guindon et al. 2010; Ronquist et al. 2012). The representative strains which selected for Phylogenetic analyses were chosen from the strains which mentioned by Woudenberg et al (2013) and obtained the sequences from NCBI. The concatenated sequences placed NFUA01, NFUA02 and NFUA03 in the clade of Alternaria tenuissima with a high confidence level (ML/BI= 100/1). A pathogenicity assay was done using isolate NFUA01 on 3-year-old L. formosana seedlings. L. formosana leaves were wounded by a sterilized needle (0.5-mm-diam), and inoculated with spore suspension (106 conidia/mL), and L. formosana leaves inoculated with sterile water were used as the control. Each treatment had 5 leaves, and incubated at 25℃ under high moisture conditions. The experiments were conducted three times. Seven days after inoculation, leaves inoculated with spore suspension showed brown leaf blights resembling the original disease symptoms, whereas the control remained healthy. The fungus was reisolated from the lesions and was confirmed as A. tenuissima based on morphologically characteristics and ITS sequence analysis. To our knowledge, this is the first report of A. tenuissima associated with leaf blight on L. formosana. The finding provides clear pathogen information for further evaluation of the disease control strategies.

Grafting Tomato to Manage Southern Blight, Prevent Yield Loss, and Increase Crop Value.

Southern blight, caused by the soilborne fungus Athelia rolfsii, has increased in frequency and severity in the southern United States since the use of methyl bromide fumigation ceased. The objective of this study was to evaluate three cultivars of sticky nightshade (Solanum sisymbriifolium), previously used as tomato rootstocks because of resistance to root-knot nematode, for resistance to southern blight. Field experiments in infested soil were done in Georgia in 2020 and 2021 and in South Carolina in 2021. Tomato cultivar Roadster was used as the scion. Control treatments included nongrafted 'Roadster' in all experiments and self-grafted 'Roadster' in Georgia. In all three experiments, all rootstocks significantly reduced incidence of southern blight and increased vigor ratings compared to control treatments (P ≤ 0.007). The rootstocks Maxifort, White Star, and SisSyn II, but not Diamond, significantly increased marketable weight (P ≤ 0.02) and crop value (P < 0.05) compared to control treatments. In South Carolina only, because of greater yields than in Georgia, net returns with Maxifort and White Star were significantly greater than net return with nongrafted 'Roadster' (P = 0.004). When the wholesale price for fresh market tomato is ≥$13/box, grafting may be an effective and economical management for southern blight.

Spore Dispersal Patterns of Colletotrichum fioriniae in Orchards and the Timing of Apple Bitter Rot Infection Periods.

Bitter rot is a major disease of apple fruit in warm and humid regions. It is caused by various species in the Colletotrichum gloeosporioides and C. acutatum species complexes, of which C. fioriniae of the C. acutatum species complex is most common in the Mid-Atlantic region of the United States. While bitter rot management begins with good cultural practices, fungicides are generally used for consistent control. Fungicides should be applied before or during infection periods, but the timing of infection is unclear due to the hemibiotrophic lifestyle of the causal species. To determine when infection periods occur, we quantified C. fioriniae spore dispersal throughout three growing seasons and compared the temporal susceptibility of apples in two seasons of field trials. Spores were detected in rainwater from bud break to leaf drop, with the highest spore quantities in the summer and early fall correlating with optimal temperatures for C. fioriniae. Late-season-inoculated fruit had more bitter rot than early-season-inoculated fruit, but this was also positively correlated with periods of optimal temperatures and moisture for infection. In the context of previous experiments, these results suggest that infection periods are primarily determined by temperature and moisture rather than apple fruit phenology. Based on the relative numbers of spores and biotrophic and necrotrophic infections, only a tiny proportion of spores establish viable biotrophic infections, but a relatively high proportion of biotrophic infections switch to necrotrophy. We suggest bitter rot management should focus on preventing initial biotrophic infections by protecting apples during weather conditions that favor infection.

Probiotic Bacteria, Anaerobic Soil Disinfestation, and Mustard Cover Crop Biofumigation Suppress Soilborne Disease and Increase Yield of Strawberry in a Perennial Organic Production System.

Black root rot complex and crown rot of strawberry caused by soilborne fungi limit sustainable strawberry production in the northeastern United States, especially in perennial systems, including matted row and plasticulture. As pathogen populations build up over time in the rhizosphere and infect the root system, feeder roots are pruned, which diminishes nutrient and water uptake and causes stunted plant growth or death. Alternative management options are needed for many organic and small growers who can't use chemical fumigants due to new regulations and potential health hazards. Strawberry plug plants were grown on beneficial microbe-inoculated or uninoculated planting mix followed by transplanting in fruiting field plots that either was biofumigated with mustard cover crop (MCC), anaerobically disinfested (ASD), or left untreated. Different combinations of plug plants and field plot treatments were used to determine the efficacy of individual treatments or synergistic effects from combination treatment. Plug plants were transplanted in pretreated plastic mulched raised beds and grown following a typical organically recommended production system. Plants grown on TerraGrow (TG)-inoculated planting mix showed enhanced plant vigor in the fruiting field compared with untreated plants. Weeds that grew through planting holes were significantly (P ≤ 0.045) suppressed in ASD plots compared with untreated plots in the first year. Plants treated with a combination treatment of TG and ASD had significantly higher fruit yield in both years (2019 and 2020), although the difference was greater in the second year. Plant vigor and survival in treated plots except MCC were also significantly higher in the second year compared with the untreated control. Suppression of pathogenic microbes and plant vigor improvement in treated plots appear to be the factors providing beneficial effects and higher net economic return. Taken together, our results suggest that a combination of beneficial microbes and ASD could be an alternative to synthetic fumigation in a perennial strawberry production system.

Topdressing Biochar Compost Mixtures and Biological Control Organism Applications Suppress Foliar Pathogens in Creeping Bentgrass Fairway Turf.

Biochar, compost, and biological control agents can suppress pathogens on their own; however, their reliability and efficacy are not as acceptable as synthetic fungicides commonly used to suppress pathogens. A multiyear field study was initiated to evaluate combinations of monthly applications of a biochar compost mixture and weekly or biweekly Bacillus subtilis QST713 applications for their ability to suppress foliar pathogens on a creeping bentgrass (Agrostis stolonifera L.) fairway and to measure their impact on strain QST713 establishment. Disease severity and turfgrass quality were measured every 14 days throughout the growing season. Populations of strain QST713 were quantified by quantitative PCR analysis on DNA extracted from foliage samples collected throughout the trial. Biochar compost mixture applications increased turfgrass quality in both years of the study and reduced dollar spot (Clarireedia jacksonii Salgado-Salazar) severity in 2021. Weekly strain QST713 applications reduced copper spot (Gloeocercospora sorghi D. C. Bain & Edgerton) severity compared with biweekly applications and the nontreated control in 2020, yet monthly biochar compost mixture with weekly strain QST713 applications completely suppressed copper spot in 2021. Populations of strain QST713 were highest in weekly treated plots, and monthly biochar compost mixture applications did not affect strain QST713 establishment. Although there was not an interaction between biochar compost mixture and strain QST713 applications, implementing both in a season-long program will benefit turfgrass health and reduce disease severity.

Characterization of Volatile Organic Compounds Produced by Bacillus siamensis YJ15 and Their Antifungal Activity Against Botrytis cinerea.

To develop an effective and environmentally safe strategy to control postharvest gray mold caused by Botrytis cinerea, Bacillus siamensis strain YJ15 isolated from blueberry was used to test the biocontrol potential. It is interesting to find that the volatile organic compounds (VOCs) emitted from strain YJ15 exhibited significant antifungal activity against Botrytis cinerea as well as 11 other plant-pathogenic fungi, with a percentage of mycelial growth inhibition from 74.96 to 92.81%. Additionally, VOCs from strain YJ15 could reduce significantly the disease incidence and lesion diameter with the increasing of fermentation time, indicating great biocontrol potential for controlling blueberry postharvest gray mold. Furthermore, the VOCs were collected by using headspace solid-phase microextraction fiber, and the composition of VOCs was further revealed by using gas chromatography coupled with quadruple mass spectrometry. In total, 24 kinds of VOCs, including 5 alkanes, 2 aldehydes, 3 ketones, 5 alcohols, 1 alkene, 5 acids and esters, 2 aromatic compounds, and 1 sulfur compound, were emitted at 1, 3, 5, and 7 days after inoculation. Among these VOCs, eight antifungal VOCs could inhibit mycelial growth of B. cinerea. It is important to highlight that, although 1-butanol and 3-methyl-1-butanol were the most abundant compounds, 2-ethylhexanol, 1-heptanol, and 1,3-xylene have proved to be more toxic to B. cinerea than 3-methyl-1-butanol, propanethioic acid, 2,2-dimethyl-, ethyl 2-methylbutyrate, 2-heptanone, and 1-butanol, which provide new, promising biofumigants for the control of postharvest gray mold caused by B. cinerea.

First Report of Lecanicillium aphanocladii causing rot of Morchella sextelata in China.

Morel mushroom (Morchella spp.) is a rare edible fungus with high nutritional and medicinal value. In China they are cultivated in sandy soils in greenhouses and production of fresh mushrooms reached 10,000 tons in 2019. However, from 2019 to 2020, a serious rot disease with 30% natural incidence was observed on M. sextelata at a mushroom farm in Pinghu (N30°39', E121°2'), Zhejiang province of China. The symptoms mainly occurred after the first flush in the early February. First, a small white mold-like symptoms appeared on the surface or the pinnacle of pileus. Then the lesion developed to encircle the pileus and spread gradually to the stipe. The lesions expanded rapidly at high temperature (>20 °C) and humidity (>70%). In the final stages of infection, the fruiting bodies became soft with white molds. The pathogen was isolated from the margin of the lesions by plating onto potato dextrose agar (PDA) and incubated at 25 °C in the dark. Colonies on PDA grew fast, reaching 60 mm in 7 days at 25 °C, and were white to cream in color, while the back of colonies appeared red to brick-red gradually. Conidiogenous cell was solitary or in whorls of 2-4, flask-shaped in the beginning, and tapered into a thread-like neck. Conidia were borne at the tips of conidiogenous cells, were oval to sub-globose, and ranged from 1.2-2.0 µm in width and 3.2-4.3 µm in length. All these characteristics were consistent with those of Lecanicillium aphanocladii (Zare R and Gams W. 2001). To confirm the identity of the pathogen (L. aphanocladii strain G1), the genomic fragments for the internal transcribed spacer (ITS) and RNA polymerase II second largest subunit (RPB2) gene of the isolate were amplified by PCR (White et al. 1990; Zhou et al. 2020). The resulting sequence was deposited in GenBank with accession No. OL629617 and No. ON005041, respectively. BLAST results showed >99% identity with those of L. aphanocladii (MG593981.1 and KM283853.1, respectively). Concatenated sequences of the two genes in L. aphanocladii strain G1 were used to conduct a phylogenetic analysis using Bayesian inference (BI) and maxium likelihood (ML) methods in MEGA6 (Tamura et al. 2013). The pathogen was grown in PDB medium at 25 °C, 200 r/min for 14 days, and after which conidial suspension (1×107conidia/mL) was prepared by filtration with four layers of sterile gauze. A pathogenicity test was performed by spraying on ten fruit bodies of M. sextelata and cultured in 20 °C and 90 to 95% relative humidity for 7 days. The test results showed that the pathogen infected the pileus and developed into white mold-like lesion, gradually spread to the stipe, and eventually the whole fruiting body became soft with white molds. The pathogen was re-isolated from infected fruiting bodies and was confirmed to be L. aphanocladii, based on morphological characteristics and the ITS, RPB2 sequence. Meanwhile,the control M. sextelata was sprayed with PDB medium and grew normally without any symptoms. L. aphanocladii has been reported on cultivated fungi such as Agaricus bisporus and A. bitorquis in Europe (Zare & Gams 2001) as well as more recently on Tremella fuciformis in China (Liu et al 2018). To our knowledge, this is the first report of L. aphanocladii causing rot of M. sextelata. According to the disease observation in the farm of Pinghu, this rot disease breaks out and spreads fast, and is getting worse ever year, resulting in a huge loss of yield and commodity value. It is a big concern to producers of this edible fungus.

Impact of Calonectria Diseases on Ornamental Horticulture: Diagnosis and Control Strategies.

Diseases caused by fungi in the genus Calonectria pose a significant threat to the ornamental horticulture industries in Europe and the United States. Calonectria spp. are particularly challenging pathogens to manage in ornamental production systems and the urban landscape for multiple reasons. A high level of species diversity and poorly resolved taxonomy in the genus makes proper pathogen identification and disease diagnosis a challenge, though recent molecular phylogenetic studies have made significant advances in species delimitation. From a disease management perspective, Calonectria spp. produce long-lived survival structures (microsclerotia) that contaminate nursery production systems and can survive multiple years in the absence of a susceptible plant host. Latent infection of plant material is poorly understood but likely contributes to long-distance dissemination of these fungal pathogens, including the clonal Calonectria spp. responsible for the global emergence of boxwood blight. Breeding for disease resistance represents a sustainable strategy for managing Calonectria diseases but is challenging due to the perennial nature of many ornamental plants and high levels of susceptibility in commercial cultivars. Ultimately, long-term sustainable management of Calonectria diseases will require an improved understanding of pathogen biology as well as integration of multiple disease management strategies.

Refinement of Nonantibiotic Spray Programs for Fire Blight Control in Organic Pome Fruit.

Fire blight-susceptible, certified organic pome fruit is produced on 9,000 ha in the Pacific Northwest region of the United States with acreage continuing to expand despite a 2014 prohibition on antibiotics as allowable materials for infection suppression. Nonantibiotic practices for fire blight pathogen suppression mirror conventional management, but the full-bloom-to-petal-fall period when antibiotics are typically sprayed for fire blight control continues to receive research scrutiny owing to drawbacks and weaknesses of alternative materials. As solitary treatments, effective nonantibiotic materials (e.g., a yeast biocontrol, soluble coppers, and potassium aluminum sulfate) raise the risk of a crop-value-reducing, phytotoxic response termed "fruit russeting." Conversely, materials with less russeting risk (e.g., Bacillus-based biorationals) are less effective for fire blight control. Spray programs using a sequence of materials applied from midbloom to petal fall have the potential to provide high levels of protection with reduced russeting risk. In orchard trials, the effects of nonantibiotic spray programs on the epiphytic population size of Erwinia amylovora in flowers, yeast biocontrol population size, floral pH, infection suppression, and fruit russeting revealed strategies for sequencing sprays of nonantibiotic materials. The yeast biocontrol, Blossom Protect (Aureobasidium pullulans), sprayed at 70% bloom, was an important contributor to fire blight pathogen suppression as was the soluble copper material, Previsto, when applied at full bloom. Choice of material for the petal-fall spray timing was important to fruit russeting risk but apparently less important to overall infection incidence. Consequently, treatment programs of Blossom Protect at 70% bloom, a soluble copper at full bloom, and a Bacillus-based biorational at petal fall, best balance the quality of infection suppression with the risk of fruit russeting.

Investigating Chemical and Biological Control Applications for Pythium Root Rot Prevention and Impacts on Creeping Bentgrass Putting Green Rhizosphere Bacterial Communities.

Pythium root rot (PRR) is a disease that can rapidly devastate large swaths of golf course putting greens, with little recourse once symptoms appear. Golf courses routinely apply preventive fungicides for root diseases, which may alter the rhizosphere microbiome, leading to unintended effects on plant health. A multiyear field trial was initiated on a 'T-1' creeping bentgrass (Agrostis stolonifera L. cultivar T-1) putting green in College Park, Maryland to evaluate preventive PRR management for disease suppression and effects on rhizosphere bacterial communities. Fungicides commonly used to prevent PRR and a biological fungicide were repeatedly applied to experimental plots throughout the growing season. Rhizosphere samples were collected twice annually from each plot for evaluation of rhizosphere bacterial communities through amplicon sequencing and monitoring of biological control organism populations via quantitative PCR. Cyazofamid was the only treatment to suppress PRR in both years compared with the control. Fosetyl-Al on a 14-day interval and Bacillus subtilis QST713 also reduced PRR severity in 2019 compared with the nontreated control. Treatments did not significantly affect bacterial diversity or relative abundances of bacterial classes; however, seasonal environmental changes did. Repeated rhizosphere-targeted applications of B. subtilis QST713 appear to have established the bacterium into the rhizosphere, as populations increased between samples, even after applications stopped. These findings suggest that QST713 may reduce pathogen pressure when repeatedly applied and can reduce fungicide usage during periods of low PRR pressure.