Dark leaf spot (Alternaria brassicicola) on Chinese cabbage: spatial patterns

2005 ◽  
Vol 56 (7) ◽  
pp. 699 ◽  
Author(s):  
L. Y. Chen ◽  
T. V. Price ◽  
M. J. Silvapulle
Keyword(s):  
Chinese Cabbage ◽  
Leaf Spot ◽  
Disease Incidence ◽  
Field Trials ◽  
Alternaria Brassicicola ◽  
Disease Spread ◽  
Distance Class ◽  
Maximum Information ◽  
Spatial Spread ◽  
Core Cluster

The spatial spread of dark leaf spot caused by Alternaria brassicicola on Chinese cabbage was characterised over 2 years. The study was conducted in 2 field trials using ordinary runs, mapping, spatial autocorrelation, and 2-dimensional distance class analyses. Diseased plants were generally clustered and cluster orientation coincided with the line of inoculation. Disease spread was greater within than across rows. The maximum number of spatial lags with significantly positive autocorrelations occurred when disease incidence levels reached 20–80% in summer 1993–94. Core cluster size generally increased with disease incidence. Two-dimensional distance class analysis was the best analytical method among those used in describing spatial spread of the disease as it did not only provide maximum information but also considered missing data.

Dark leaf spot (Alternaria brassicicola) on Chinese cabbage: temporal spread and its influencing factors

2002 ◽  
Vol 53 (10) ◽  
pp. 1095 ◽  
Author(s):  
L. Y. Chen ◽  
T. V. Price
Keyword(s):  
Chinese Cabbage ◽  
Wind Direction ◽  
Leaf Spot ◽  
Irrigation System ◽  
Disease Incidence ◽  
Field Trials ◽  
Alternaria Brassicicola ◽  
Disease Spread ◽  
Average Wind ◽  
Temporal Spread

Temporal spread of dark leaf spot on Chinese cabbage was studied in experimental plots for 2 years. The effect of row orientation, the orientation of inoculated plants, and irrigation system on disease incidence and the effect of average wind direction on disease spread were investigated. A line source of inoculum in each plot was used for the 1993–94 summer and the 1994 spring–summer field trials, and 3 line sources for a 1995 autumn field trial. Disease progressed more rapidly in the 1993–94 summer than in the 1995 autumn. Disease epidemic did not develop in the 1994 spring–summer when environmental conditions were unfavourable. Disease incidence was higher in plots with row orientation parallel to the average wind direction than in plots with row orientation at right angles to the average wind direction for both the 1993–94 summer and the 1995 autumn trials. In summer 1993–94, across-row inoculation resulted in higher disease incidence than row inoculation did. No difference in disease incidence occurred between channel irrigation and overhead irrigation plots. Secondary infections always occurred adjacent to the source of inoculum and disease spread was influenced by the prevalent wind direction.

scholarly journals Effective Biomass Reduction of the Invasive Weed Species Banana Poka by Septoria Leaf Spot

Plant Disease ◽  
2001 ◽  
Vol 85 (4) ◽  
pp. 357-361 ◽  
Author(s):  
Eduardo E. Trujillo ◽  
Chris Kadooka ◽  
Victor Tanimoto ◽  
Steve Bergfeld ◽  
Glenn Shishido ◽  
...  
Keyword(s):  
Leaf Spot ◽  
Disease Incidence ◽  
Severe Disease ◽  
Disease Spread ◽  
Leaf Spot Disease ◽  
Native Forest ◽  
Invasive Weed ◽  
Disease Epidemics ◽  
Biomass Reduction ◽  
Septoria Leaf Spot

Inoculations of Septoria passiflorae for biological control of banana poka (Passiflora tripartita var. tripartita) at different forest sites in Hawaii, Kauai, and Maui resulted in successful establishment of the Septoria leaf spot disease at all sites during 1996. Semi-annual monitoring of sites in 1997 revealed low disease incidence and no disease spread to adjacent non-inoculated plants. Site inspections in March 1998 revealed light disease epidemics causing visible defoliation at inoculated sites on Kauai and Maui. Banana poka biomass reduction at sites with light epidemics of the disease in Kauai and Maui were estimated to be less than 10% in 1998, whereas in 1999 biomass reduction ranged from 50 to 95%. Five of 11 inoculation sites in 1996 on the island of Hawaii showed no disease. These five sites on Kaloko had frequent acid rainfall averaging 3.2 pH, which inhibited spore germination and infection. Six sites, free of acid rain, three at Hilo Forest Reserve and three at Puuwaawaa Wildlife Sanctuary, had severe disease epidemics by 1998, and vine defoliation was >90%. Widespread epidemics of the disease occurred in 1999, resulting in estimated 80 to 95% biomass reductions in more than 2,000 hectares of native forest infested with banana poka.

Assessing resistance to spring black stem and leaf spot of alfalfa caused by Phoma spp.

2004 ◽  
Vol 84 (1) ◽  
pp. 311-317 ◽  
Author(s):  
H. Wang ◽  
S. F. Hwang ◽  
K. F. Chang ◽  
B. D. Gossen ◽  
G. D. Turnbull ◽  
...  
Keyword(s):  
Medicago Sativa ◽  
Leaf Spot ◽  
Similar Pattern ◽  
Disease Incidence ◽  
Field Trials ◽  
Disease Reaction ◽  
Detached Leaf ◽  
Controlled Conditions ◽  
Detached Leaves ◽  
Phoma Sclerotioides

The disease reaction of alfalfa (Medicago sativa) cultivars to spring black stem was evaluated in field trials and greenhouse experiments. In field trials, differences in cultivar reaction to leaf spot (predominantly spring black stem) were observed in 9 of 16 station years. The reaction of certain cultivars was consistent across most trials, but other cultivars were quite variable. Under controlled conditions, one isolate each of Phoma sclerotioides and P. exigua produced symptoms on alfalfa leaves that were similar to those caused by P. medicaginis. These results indicate that P. medicaginis is not the only pathogen responsible for symptoms of spring black stem on alfalfa in the prairie region. In a detached-leaf study, one isolate each of P. medicaginis, P. sclerotioides and P. exigua produced leaf lesions on all 18 alfalfa cultivars assessed. Disease incidence in Absolute, Algonquin, Pickseed 3006 and Anik (M. sativa subsp. falcata) was lower than in 630 and AC Blue J. Inoculation of eight selected cultivars using a range of spore concentrations under controlled conditions showed a similar pattern; all three isolates produced leaf lesions on all eight cultivars. Ino culation with conidial suspensions of P. medicaginis resulted in a lower disease incidence on Absolute than on Beaver. Key words: Medicago sativa, Medicago sativa subsp. falcata, Phoma medicaginis, P. sclerotioides, P. exigua, detached leaves.

scholarly journals Phytopathological and nutraceutical evaluation of cauliflower plants treated with high dilutions of arsenic trioxide

2021 ◽  
Vol 11 (40) ◽  
pp. 161-162
Author(s):  
Grazia Trebbi ◽  
Giovanni Dinelli ◽  
Ilaria Marotti ◽  
Valeria Bregola ◽  
Maurizio Brizzi ◽  
...  
Keyword(s):  
Fungal Infection ◽  
Arsenic Trioxide ◽  
Plant Resistance ◽  
Leaf Spot ◽  
Natural Infection ◽  
Field Trials ◽  
Alternaria Brassicicola ◽  
Leaf Spot Disease ◽  
Glucosinolate Content ◽  
Infection Level

Introduction: This research aimed at verifying the effects of highly diluted (HD) treatments on cauliflower (Brassica oleracea L.) plants both healthy and inoculated by the fungus Alternaria brassicicola, causing the dark leaf spot disease. In vitro spore germination assays (A), growth chamber experiments (B) and field trials (C) were performed. Material and Methods: (A): spore suspensions were prepared in HD treatments and their inhibiting effect on germination was recorded microscopically after incubation at 25°C for 5 h. (B): the same treatments were tested in plants artificially inoculated with the fungus. The infection level on leaves was blindly evaluated by a previously defined infection scale. (C): the field was divided into plots according to a complete randomized block design. In the first trial (i), plants were artificially inoculated and weekly treated; the infection level was evaluated on cauliflower heads. The second trial (ii) was performed on the same field with the aim to induce a natural infection, mediated by infected crop residues. Measurement endpoints concerned the evaluation of some physiological parameters along with the glucosinolate content on cauliflower heads. Results: (A): arsenic trioxide (As 35x and 35x diluted 1:5000) and Cuprum 5x induced highly significant inhibition of germination rate (-60%) vs. control. (B): As 35x and Cu 3 g/l induced a significant decrease of mean infection level (-50%). (C): in (i), a significant reduction of disease symptoms on heads was recorded for As 35x and Cu 3 g/l (-45%). In (ii) natural fungal infection did not occur due to dry weather conditions; physiological and nutraceutical analyses of healthy heads demonstrated that As 35x induced a significant increase of both head size and glucosinolate content. Discussion: Some evidences on the efficacy of arsenic, at different decimal and centesimal HD, in fungal and viral disease control were previously reported [1]. In the present study the efficacy of HD arsenic in dark leaf spot control in field has been shown for the first time: since fungal inoculation was performed on the leaves before flowering, we can hypothesize that this treatment induced an increase of plant resistance to fungal infection. Conclusions: This research showed the possibility of using HD arsenic in agriculture (“agrohomeopathy”), as it increased both plant resistance to fungal infection and the content of glucosinolates, ie secondary metabolites involved in plant resistance mechanisms [2] and considered as “plant food protection agents” [3]. Acknowledgments: Authors declare there is no conflict of interest. This research has been supported by Marche Region. A grateful acknowledgement to Dr. Leonardo Valenti for his support to this research. The authors thank Laboratoires Boiron srl for the grant awarded to one of the author Dr. Grazia Trebbi. Finally, authors are grateful to Cemon srl for financial support of glucosinolate analyses. We had full access to all the data in this study and we take responsibility for the integrity of the data and the accuracy of the data analysis Keywords: cauliflower, arsenic trioxide, Alternaria brassicicola, glucosinolates References [1] Betti L, Trebbi G, Majewsky V, Scherr C, Shah-Rossi D, Jäger T, et al. Use of homeopathic preparations in phytopathological models and in field trials: a critical review. Homeopathy 2009; 98: 244-266. [2] Ménard R, Larue J-P, Silué D, Thouvenot D. Glucosinolates in cauliflower as biochemical markers for resistance against downy mildew. Phytochemistry 1999; 52: 29-35. [3] Talalay P, Fahey JW. Phytochemicals from Cruciferous plants protect against cancer by modulating carcinogen metabolism. J Nutr. 2001; 131:3027S- 3033S.

scholarly journals The interplay of spatial spread of COVID-19 and human mobility in the urban system of China during the Chinese New Year

2020 ◽  
pp. 239980832095421 ◽  
Author(s):  
Xiaoyan Mu ◽  
Anthony Gar-On Yeh ◽  
Xiaohu Zhang
Keyword(s):  
Human Mobility ◽  
Disease Incidence ◽  
Urban System ◽  
Disease Spread ◽  
New Wave ◽  
Spatial Spread ◽  
Mobility Data ◽  
Rapid Spread ◽  
Disease Spreading ◽  
Scientific Attention

The rapid spread of infectious diseases is devastating to the healthcare systems of all countries. The dynamics of the spatial spread of epidemic have received considerable scientific attention. However, the understanding of the spatial variation of epidemic severity in the urban system is lagging. Using synchronized epidemic data and human mobility data, integrated with other multiple-sourced data, this study examines the interplay between disease spread of coronavirus disease (COVID-19) and inter-city and intra-city mobility among 319 Chinese cities. The results show a disease spreading process consisting of a major transfer (inter-city) diffusion before the Chinese New Year and a subsequent local (intra-city) diffusion after the Chinese New Year in the urban system of China. The variations in disease incidence between cities are mainly driven by inter-city mobility from Wuhan, the epidemic center of COVID-19. Cities that are closer to the epidemic center and with more population in the urban area will face higher risks of disease incidence. Warm and humid weather could help mitigate the spread of COVID-19. The extensive inter-city and intra-city travel interventions in China have reduced approximately 70% and 40% inter-city and intra-city mobility, respectively, and effectively slowed down the spread of the disease by minimizing human to human transmission together with other disease monitoring, control, and preventive measures. These findings could provide valuable insights into understanding the dynamics of disease spread in the urban system and help to respond to another new wave of pandemic in China and other parts of the world.

scholarly journals Development of Lettuce Breeding Lines Resistant to Bacterial Leaf Spot

HortScience ◽  
2005 ◽  
Vol 40 (4) ◽  
pp. 1098A-1098 ◽  
Author(s):  
Ryan J. Hayes ◽  
Carolee T. Bull ◽  
Polly H. Goldman ◽  
Edward J. Ryder
Keyword(s):  
Leaf Spot ◽  
Xanthomonas Campestris ◽  
Disease Incidence ◽  
Field Trials ◽  
Control Measures ◽  
Bacterial Leaf Spot ◽  
Sources Of Resistance ◽  
Breeding Lines ◽  
Overhead Irrigation ◽  
Lettuce Breeding

Bacterial leaf spot of lettuce caused by Xanthomonas campestris pv. vitians (Xcv) is an important lettuce disease in California. No adequate control measures have been found, although resistance exists in several heirloom cultivars. Deployment of cultivars resistant to bacterial leaf spot will reduce these periodic and costly disease events. The objectives of this research were to 1) identify new sources of resistance within modern crisphead cultivars and 2) select for resistance in `Salad Crisp' × `Iceberg' progeny. Field plots were established and grown with overhead irrigation, and a three-strain mixture of Xcv was applied until runoff 1 week after thinning at 1 × 109 CFU/mL. Twenty-six crisphead cultivars were tested in unreplicated field trials and rated on a 1 (susceptible) to 4 (resistant) scale. Selection was carried out between and within families from the F2 to F4 generation. Sixteen F3 families were evaluated in unreplicated plots, and 12 F5 families were tested in replicated plots for disease incidence and severity. No usable levels of resistance were identified in the modern crisphead cultivars tested to date. All F3 families had resistance greater than `Iceberg', and 19 plants from eight families were selected for further breeding. Subsequently, 12 plants from two F4 families were selected. Replicated trials of 12 F5 families indicated that all lines have disease severity comparable to both parents. Breeding lines from crosses to `Salinas 88' are currently being developed.

scholarly journals Analysis of the Spatial Pattern of Strawberry Angular Leaf Spot in California Nursery Production

2017 ◽  
Vol 107 (10) ◽  
pp. 1243-1255 ◽  
Author(s):  
Christophe Gigot ◽  
William Turechek ◽  
Neil McRoberts
Keyword(s):  
Spatial Pattern ◽  
Leaf Spot ◽  
Management Practices ◽  
Disease Incidence ◽  
Spatial Association ◽  
Angular Leaf Spot ◽  
Disease Spread ◽  
Point Pattern ◽  
Common Disease ◽  
Nursery Production

In California, angular leaf spot (ALS) is a common disease in strawberry nursery production, and a major concern for nurseries wishing to export plants. As the spatial pattern of a disease can offer insight into pathogen source, mode of dissemination, and how current crop management practices affect epidemic development, an understanding of the spatial pattern of ALS would allow nursery growers to make informed decisions regarding disease management. Ninety-seven field assessments of disease incidence were performed at different nursery locations in 2014 and 2015 to quantify ALS spatial pattern under commercial conditions. Both point-pattern and geostatistical statistical procedures were used to analyze the data. The spatial pattern of ALS was characterized by a high degree of heterogeneity, as indicated by high median values of the beta-binomial distribution’s theta parameter (0.643), and the index of dispersion, D (4.218). The binary power law provided a robust description of the data with estimated slope and intercept parameters significantly greater than 1 and 0, respectively (P < 0.001). Spatial analysis by distance indices (SADIE) detected significant nonrandom spatial arrangements for 64% of the data sets. Analysis of directional disease spread showed a strong spatial association between sampling units along the same planting row. This suggests that recurrent crop operations during the growing season play a significant role in ALS spread and should be taken into account to improve disease control.

The bioactivity and efficacy of benzovindiflupyr against Corynespora cassiicola, the causal agent of cucumber Corynespora leaf spot

Plant Disease ◽  
2021 ◽  
Author(s):  
Jiamei Zhu ◽  
Xiuhuan Li ◽  
Lingyan Zhang ◽  
Yangyang Gao ◽  
Wei Mu ◽  
...  
Keyword(s):  
Leaf Spot ◽  
Integrated Management ◽  
Disease Incidence ◽  
Field Trials ◽  
Corynespora Cassiicola ◽  
Atp Production ◽  
Control Failure ◽  
Efficient Alternative ◽  
The Mean ◽  
And Control

Corynespora cassiicola, which causes Corynespora leaf spot, results in considerable yield loss of cucumber grown in greenhouses. Frequent reports of reduced efficacy and control failure of fungicides warrant new, efficient alternative chemistries. In the present study, the sensitivity of C. cassiicola to benzovindiflupyr was evaluated using a collection of 81 isolates collected from Shandong, China. The mean EC50 values for mycelial growth, spore germination and germ tube elongation of C. cassiicola were 0.69 ± 0.44, 0.12 ± 0.063 and 0.13 ± 0.076 µg mL-1, respectively. Benzovindiflupyr treatment led to a reduced respiration rate and ATP production of C. cassiicola and decreased spore pathogenicity by 21.9% on average. Additionally, detached cucumber leaves sprayed with fungicides before or after inoculation were used to assess the efficacy of benzovindiflupyr against C. cassiicola. Benzovindiflupyr (150 µg mL-1) exhibited preventive and curative efficacies of 86.9% and 77.1%, respectively. Benzovindiflupyr at 150 g a.i. ha-1 provided over 70% efficacy in field trials performed in 2018 and 2019, which was significantly higher than that of the reference fungicides fluopyram and fluxapyroxad at the same dose. Furthermore, the yield of commercial cucumber increased as disease incidence decreased. Our findings pave the way for the introduction of benzovindiflupyr in the integrated management of Corynespora leaf spot.

scholarly journals Variation in human mobility and its impact on the risk of future COVID-19 outbreaks in Taiwan

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Meng-Chun Chang ◽  
Rebecca Kahn ◽  
Yu-An Li ◽  
Cheng-Sheng Lee ◽  
Caroline O. Buckee ◽  
...  
Keyword(s):  
Disease Surveillance ◽  
Initial Conditions ◽  
Human Mobility ◽  
Human Movement ◽  
Disease Spread ◽  
Spatial Spread ◽  
Movement Data ◽  
Intercity Travel ◽  
Travel Restrictions ◽  
The Impact

Abstract Background As COVID-19 continues to spread around the world, understanding how patterns of human mobility and connectivity affect outbreak dynamics, especially before outbreaks establish locally, is critical for informing response efforts. In Taiwan, most cases to date were imported or linked to imported cases. Methods In collaboration with Facebook Data for Good, we characterized changes in movement patterns in Taiwan since February 2020, and built metapopulation models that incorporate human movement data to identify the high risk areas of disease spread and assess the potential effects of local travel restrictions in Taiwan. Results We found that mobility changed with the number of local cases in Taiwan in the past few months. For each city, we identified the most highly connected areas that may serve as sources of importation during an outbreak. We showed that the risk of an outbreak in Taiwan is enhanced if initial infections occur around holidays. Intracity travel reductions have a higher impact on the risk of an outbreak than intercity travel reductions, while intercity travel reductions can narrow the scope of the outbreak and help target resources. The timing, duration, and level of travel reduction together determine the impact of travel reductions on the number of infections, and multiple combinations of these can result in similar impact. Conclusions To prepare for the potential spread within Taiwan, we utilized Facebook’s aggregated and anonymized movement and colocation data to identify cities with higher risk of infection and regional importation. We developed an interactive application that allows users to vary inputs and assumptions and shows the spatial spread of the disease and the impact of intercity and intracity travel reduction under different initial conditions. Our results can be used readily if local transmission occurs in Taiwan after relaxation of border control, providing important insights into future disease surveillance and policies for travel restrictions.

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