scholarly journals Comparison of decision methods to initiate fungicide applications against cercospora blight of carrot

2005 ◽  
Vol 76 (3) ◽  
pp. 91-99 ◽  
Author(s):  
V. Abraham ◽  
A.C. Kushalappa ◽  
O. Carisse ◽  
G. Bourgeois ◽  
P. Auclair
Keyword(s):  
High Risk ◽  
Disease Incidence ◽  
Forecasting Model ◽  
Leaf Wetness ◽  
High Humidity ◽  
Yield Losses ◽  
Threshold Method ◽  
Fungicide Application ◽  
Decision Methods ◽  
Cercospora Carotae

In 1991 and 1992, two thresholds of a forecasting model were compared with two other decision methods for effectiveness in timing the first fungicide application against Cercospora blight of carrot induced by Cercospora carotae. The first fungicide application was made when : 1) the plants reached 15 cm in height (conventional method); 2) the intermediate (middle) leaves of 50% of the plants were diseased (50% disease incidence threshold method); 3) the cumulative infection equivalence (CE) was 14 (forecasting model CE 14); and 4) the CE was 18 (forecasting model CE 18). In all four treatments, subsequent applications of fungicide were made at 10-d intervals when there was no rain, and at 7-d intervals when there was rain. The CE was calculated based on duration of leaf wetness and temperature during the wet period, corrected for high humidity and interrupted wet periods, and was cumulative starting at crop emergence. For thresholds of CE 14 and CE 18, no yield losses were observed and the total number of fungicide applications needed was lower compared to conventional and 50% disease incidence threshold methods. In a separate study, the CE thresholds were related to the percentage of commercial fields that reached disease incidence thresholds of 50, 80 and 100% to establish low risk (CE 11-15) and high risk (CE 16-20) thresholds. The forecasting of low and high risk CE thresholds were too late for 3 and 19% of the commercial fields because those fields had more than 50 and 80% of the plants diseased, respectively.

scholarly journals A Peri-Implant Disease Risk Score for Patients with Dental Implants: Validation and the Influence of the Interval between Maintenance Appointments

2019 ◽  
Vol 8 (2) ◽  
pp. 252 ◽  
Author(s):  
Miguel de Araújo Nobre ◽  
Francisco Salvado ◽  
Paulo Nogueira ◽  
Evangelista Rocha ◽  
Peter Ilg ◽  
...  
Keyword(s):  
High Risk ◽  
Risk Score ◽  
Disease Risk ◽  
Disease Incidence ◽  
Risk Groups ◽  
Risk Profile ◽  
Moderate Risk ◽  
C Statistic ◽  
Disease Risk Score ◽  
Very High

Background: There is a need for tools that provide prediction of peri-implant disease. The purpose of this study was to validate a risk score for peri-implant disease and to assess the influence of the recall regimen in disease incidence based on a five-year retrospective cohort. Methods: Three hundred and fifty-three patients with 1238 implants were observed. A risk score was calculated from eight predictors and risk groups were established. Relative risk (RR) was estimated using logistic regression, and the c-statistic was calculated. The effect/impact of the recall regimen (≤ six months; > six months) on the incidence of peri-implant disease was evaluated for a subset of cases and matched controls. The RR and the proportional attributable risk (PAR) were estimated. Results: At baseline, patients fell into the following risk profiles: low-risk (n = 102, 28.9%), moderate-risk (n = 68, 19.3%), high-risk (n = 77, 21.8%), and very high-risk (n = 106, 30%). The incidence of peri-implant disease over five years was 24.1% (n = 85 patients). The RR for the risk groups was 5.52 (c-statistic = 0.858). The RR for a longer recall regimen was 1.06, corresponding to a PAR of 5.87%. Conclusions: The risk score for estimating peri-implant disease was validated and showed very good performance. Maintenance appointments of < six months or > six months did not influence the incidence of peri-implant disease when considering the matching of cases and controls by risk profile.

scholarly journals Investigation of Botrytis Cinerea Risk Forecasting Model of Strawberry in Lithuania

2013 ◽  
Vol 67 (2) ◽  
pp. 195-198 ◽  
Author(s):  
Neringa Rasiukevičiūtė ◽  
Alma Valiuškaitė ◽  
Elena Survilienė-Radzevičė ◽  
Skaidrė Supronienė
Keyword(s):  
Disease Management ◽  
Botrytis Cinerea ◽  
Air Temperature ◽  
Grey Mould ◽  
Management Systems ◽  
Forecasting Model ◽  
Leaf Wetness ◽  
Risk Of Infection ◽  
Risk Forecasting ◽  
Risk Probability

Grey mould, caused by Botrytis cinerea Pers.:Fr. is one of the most important strawberry diseases in Lithuania, like in other countries, where strawberries are grown. The efficiency of different disease management systems were analyzed at the Institute of Horticulture in 2010-2011. The B. cinerea risk probability at various regions of Lithuania was analyzed according to iMETOS ®sm grey mould risk forecasting model. Strawberry grey mould risk forecasting model indicates the risk of infection periods on the basis of the interaction between air temperature and leaf wetness duration. The model calculates how favourable is the period for the risk of infection. In periods where the risk is consistent (more than three days), higher than 60 points, a spray against grey mould should be applied. iMETOS®sm grey mould risk forecasting model gives the opportunity to optimize the usage of fungicides and reduce the number of applications and allows more efficient, ecologically and economically accepted control of strawberries grey mould.

scholarly journals The influence of the timing and methods of harvesting the seed grass of the eastern goat’s rue (Galega orientales Lam.) on the yield and sowing quality of seeds

2021 ◽  
Vol 901 (1) ◽  
pp. 012042
Author(s):  
V N Zolotarev
Keyword(s):  
Comparative Assessment ◽  
Optimal Harvesting ◽  
High Humidity ◽  
Yield Losses ◽  
High Moisture Content ◽  
High Moisture ◽  
Green Beans ◽  
Grass Stand ◽  
Light Green

Abstract Eastern goat’s rue (Galega orientales Lam.) possesses high fodder productivity and accumulates a large amount of vegetative mass with high humidity for harvesting for seeds. This greatly complicates the harvesting of grass stand for seeds. One of the ways to solve this problem is to carry out desiccation of the grass stand. A complicating factor in choosing the optimal harvesting period is the extended flowering and ripening period of goat’s rue beans, the duration of which reaches 25-35 days. The use of the drug Reglon Super based on diquat is a highly effective agrotechnical method that allows increasing the collection of seeds by 24%. The desiccation of the herbage contributes to the production of seeds with high sowing qualities. The seeds with the best sowing qualities are found in beans with yellow, brown, brown or dark brown color of the beans. In light green beans, the seeds are fully formed, but have a high moisture content. Goat’s rue beans do not crack or crumble at the onset of the full ripeness phase. This allows the seed to be harvested when most of the beans are ripe. A comparative assessment of the timing and method of harvesting the seed herbage of the goat’s rue showed that with a ripening of 39% and the presence of 47% of light green and yellow beans, the yield losses ranged from 26 to 56%. The highest seed yield in one confidence interval of 422-453 kg / ha and 444 kg / ha was obtained, respectively, by direct threshing with preliminary desiccation of the grass stand in the ripening phase of 74-97% of beans or by separate harvesting when mowing into swaths during ripening 74 % beans.

scholarly journals First Report of Alternaria Leaf Spot of Almond Caused by Species in the Alternaria alternata Complex in California

Plant Disease ◽  
2001 ◽  
Vol 85 (5) ◽  
pp. 558-558 ◽  
Author(s):  
B. L. Teviotdale ◽  
M. Viveros ◽  
B. Pryor ◽  
J. E. Adaskaveg
Keyword(s):  
Alternaria Alternata ◽  
Leaf Spot ◽  
Disease Incidence ◽  
Prunus Dulcis ◽  
Leaf Spot Disease ◽  
Yield Losses ◽  
Mature Leaves ◽  
Branching Chains ◽  
Paper Towels ◽  
Industry Conference

A new leaf spot disease of almond (Prunus dulcis [Mill.] D. Webb) was observed in California in the late 1980s and was first associated with severe defoliation in the mid-1990s (1). Orchards in areas with frequent summer dews, high humidity, and little air movement sustained severe defoliation, resulting in yield losses often exceeding 50%. Symptoms occur only on leaf blades in late spring and summer. Lesions develop as small, circular, tan spots 1 to 3 mm in diameter that may enlarge to 5 to 20 mm in size. Semicircular lesions frequently develop along the leaf margins and tips. The centers of mature lesions become black with fungal sporulation. The fungi isolated from the margins of sporulating and non-sporulating lesions were identified as three species in the Alternaria alternata complex: A. alternata, A. arborescens, and A. tenuissima (2,3). Cultures grown in the dark on potato dextrose (PDA) or potato-carrot agar are grayish white to olivacious green in the former two species and dark gray and wooly in the latter species. On 5% PDA, cultures of all three species produced catenulate dictyospores that were granular to punctate (-verrucose), pale yellowish to brown or black, and had visible apical and basal pores. Conidial morphology depended on chain position; apical conidia ranged from ovoid to ellipsoid, whereas basal conidia were elliptical to obclavate. Average conidial dimensions of A. alternata and A. arborescens ranged from 20 to 28 × 8 to 10 μm. Conidia of A. alternata were produced in acropetal succession in branching chains on single, short suberect conidiophores. A. arborescens produced conidia similarly but mostly in dichotomously branching chains on short to long conidiophores. Average conidial dimensions of A. tenuissima ranged from 20 to 34 × 8 to 12 μm and they were produced in simple chains with one or two branches forming occasionally. In preliminary studies, the optimum temperature for mycelial growth on PDA for all three species ranged from 24 to 28°C. Fifty mature leaves on each of four 7- or 8-year-old almond cv. Butte trees were inoculated at 2- to 3-week intervals from mid-spring through summer in 1999 and 2000. Leaves were sprayed with aqueous suspensions containing 105 conidia per milliliter for one isolate each of A. alternata and A. arborescens and two isolates of A. tenuissima or with sterile distilled water. The shoots were covered for 72 h with plastic-lined brown paper bags containing wet paper towels. Leaves were examined for infection after 7 and 14 days. All isolates were pathogenic and produced non-sporulating lesions similar to those observed in natural infections. No symptoms were observed on noninoculated control plants. Disease incidence was low (<15%) until late June 1999 and July 2000. Inoculations in summer produced increasingly more infections, reaching incidences of 40 to 52% in September 1999 and 18 to 80% in August 2000. References: (1) J. E. Adaskaveg. 1994. Pages 5–7 in Proceedings of the 22nd Annual Almond Industry Conference. 1994. (2) J. Rotem. 1994. The genus Alternaria. Biology, Epidemiology, and Pathogenicity. APS Press, St. Paul, MN. (3) E. G. Simmons. Mycotaxon 70:325–369, 1999.

scholarly journals Incorporation of Temperature and Solar Radiation Thresholds to Modify a Lettuce Downy Mildew Warning System

2002 ◽  
Vol 92 (6) ◽  
pp. 631-636 ◽  
Author(s):  
B. M. Wu ◽  
A. H. C. van Bruggen ◽  
K. V. Subbarao ◽  
H. Scherm
Keyword(s):  
Solar Radiation ◽  
Downy Mildew ◽  
Disease Incidence ◽  
Characteristic Curve ◽  
Warning System ◽  
Effect Of Temperature ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Leaf Wetness ◽  
High Solar Radiation

The effect of temperature on infection of lettuce by Bremia lactucae was investigated in controlled environment studies and in the field. In controlled conditions, lettuce seedlings inoculated with B. lactucae were incubated at 15, 20, 25, or 30°C during a 4-h wet period immediately after inoculation or at the same temperatures during an 8-h dry period after the 4-h postinoculation wet period at 15°C. High temperatures during wet and dry periods reduced subsequent disease incidence. Historical data from field studies in 1991 and 1992, in which days with or without infection had been identified, were analyzed by comparing average air temperatures during 0600 to 1000 and 1000 to 1400 Pacific standard time (PST) between the two groups of days. Days without infection had significantly higher temperatures (mean 21.4°C) than days with infection (20.3°C) during 1000 to 1400 PST (P < 0.01) but not during 0600 to 1000 PST. Therefore, temperature thresholds of 20 and 22°C for the 3-h wet period after sunrise and the subsequent 4-h postpenetration period, respectively, were added to a previously developed disease warning system that predicts infection when morning leaf wetness lasts ≥4 h from 0600 PST. No infection was assumed to occur if average temperature during these periods exceeded the thresholds. Based on nonlinear regression and receiver operating characteristic curve analysis, the leaf wetness threshold of the previous warning system was also modified to ≥3-h leaf wetness (≥0900 PST). Furthermore, by comparing solar radiation on days with infection and without infection, we determined that high solar radiation during 0500 to 0600 PST in conjunction with leaf wetness ending between 0900 and 1000 PST was associated with downy mildew infection. Therefore, instead of starting at 0600 PST, the calculation of the 3-h morning leaf wetness period was modified to start after sunrise, defined as the hour when measured solar radiation exceeded 8 W m-2 (or 41 μmol m-2 s-1 for photon flux density). The modified warning system was compared with the previously developed system using historical weather and downy mildew data collected in coastal California. The modified system was more conservative when disease potential was high and recommended fewer fungicide applications when conditions were not conducive to downy mildew development.

Effect of In-Furrow and Early-Season Banded Applications of Fungicides on Incidence of Early Leaf Spot of Peanut

2015 ◽  
Vol 16 (4) ◽  
pp. 225-229
Author(s):  
Albert K. Culbreath ◽  
Robert C. Kemerait ◽  
Yun-Ching Tsai ◽  
Timothy B. Brenneman ◽  
Katherine L. Stevenson ◽  
...  
Keyword(s):  
Arachis Hypogaea ◽  
Leaf Spot ◽  
Field Experiments ◽  
Disease Incidence ◽  
Cercospora Arachidicola ◽  
Early Season ◽  
Fungicide Application

Field experiments were conducted in Tifton, GA, in 2012-2014 to determine the effect of in-furrow applications of prothioconazole and early-season banded applications of prothioconazole or pyraclostrobin on incidence of early leaf spot (Cercospora arachidicola) of peanut (Arachis hypogaea). In each year, border rows were planted in May as a source of inoculum for plants in the treatment plots. Plots were planted in August or September after epidemics of early leaf spot were severe in the border plots. Fungicide application regimes included two rates (100 and 200 g a.i./ha) of prothioconazole applied in-furrow at planting, and 200 g a.i./ha of prothioconazole or 164 g a.i./ha of pyraclostrobin applied concentrated in a 30-cm band 21 days after planting (DAP). Incidence (percent of leaflets with one or more leaf spot) of early leaf spot was monitored until 54 to 57 days after planting in each year. In all years, disease incidence was below 10% at 28 DAP in plots treated with 200 g a.i./ha of prothioconazole in-furrow compared to over 40% in nontreated plots at the same time. In-furrow applications of 100 g a.i./ha of prothioconazole were less effective, but suppressed leaf spot incidence compared to the control. Banded applications of either fungicide at 21 DAP resulted in a decrease in leaf spot incidence, and prevented increase in leaf spot incidence for 19 days or longer. Accepted for publication 30 November 2015. Published 3 December 2015.

scholarly journals Early Blight Control in Potato Using Disease-Orientated Threshold Values

Plant Disease ◽  
2012 ◽  
Vol 96 (1) ◽  
pp. 124-130 ◽  
Author(s):  
J. H. Leiminger ◽  
H. Hausladen
Keyword(s):  
Early Blight ◽  
Disease Incidence ◽  
Growing Season ◽  
Potato Production ◽  
Economic Damage ◽  
Optimal Timing ◽  
Threshold Values ◽  
Fungicide Application ◽  
Disease Threshold ◽  
Starch Yield

Epidemics of early blight caused by Alternaria spp. can cause significant economic damage to potato production if not adequately controlled. In order to improve control of Alternaria spp. in potato, studies were conducted to identify the optimal fungicide strategy and, if possible, to reduce the number of fungicide applications per growing season. Therefore, a disease-threshold-based framework was tested to define the optimal timing of fungicide application. The initiation and subsequent applications of fungicides were based on increases in disease incidence or severity. Adequate disease control was achieved by a three-time application with azoxystrobin, given that the applications were carried out at pivotal times in the epidemic. Targeted applications of fungicides reduced the number of sprayings required to protect starch yield. Results indicate that early blight can be effectively managed by using fungicide application thresholds based on disease progress.

scholarly journals Lessons of a stripe rust epidemic in a wheat fungicide trial in Debrecen

2014 ◽  
pp. 35-46
Author(s):  
György Kövics
Keyword(s):  
Stripe Rust ◽  
Technology Development ◽  
Yield Losses ◽  
Active Ingredients ◽  
Good Efficacy ◽  
Fungicide Application ◽  
Serious Infection ◽  
Great Yield

During the 2014 year a fungicide application trial was made as a part of technology development in Debrecen (East-Hungary). Both in this trial and across in Hungary a serious stripe rust epidemic developed and caused great yield losses. The first sympotoms were observed in April on one of trial plots and during some following weeks a serious infection grown up. On the base of 13 fungicide active ingredients and dosages by two spraying applications, their efficacy could be evaluated in stripe rust control. Picoxystrobin 250 g/L acive ingredient applied in 0.6, 0.8 and 1 L/ha dosages (Acanto), picoxystrobin 200 g/L + ciproconazole 80 g/L combined active ingredients in 0.5, 0.75, and 1 L/ha dosages (Acanto Plus), epoxiconazole 83 g/L, moreover protioconazole 125 g/L + tebuconazole 125 g/L combinations gave good efficacy, respectively. The yield of well protected plots were 5 to 8 t/ha, but the losses were 40-70% when fungicides with no sufficient efficacy in stripe rust control were applied. The great infection, which was observed on different grasses late in the Autumn, 2014 might forecast a further stripe rust epidemic for the 2015 year.

scholarly journals SEVERITY OF RAMULARIA LEAF SPOT AND SEED COTTON YIELD IN DIFFERENT SOWING TIMES

2016 ◽  
Vol 29 (3) ◽  
pp. 603-610 ◽  
Author(s):  
JOÃO PAULO ASCARI ◽  
DEJÂNIA VIEIRA DE ARAÚJO ◽  
LEONARDO DIOGO EHLE DIAS ◽  
GIOVANI JUNIOR BAGATINI ◽  
INÊS ROEDER NOGUEIRA MENDES
Keyword(s):  
Disease Control ◽  
Leaf Spot ◽  
Cotton Yield ◽  
Yield Losses ◽  
Seed Cotton ◽  
Sowing Time ◽  
Fungicide Application ◽  
Progress Curve ◽  
Ramularia Leaf Spot ◽  
Diagrammatic Scale

ABSTRACT The ramularia leaf spot (RLS) disease causes cotton yield losses. Choosing a less susceptible cultivar and a sowing time that are less favorable to the pathogen contribute to the management of this disease. The objective of this work was to evaluate the severity of ramularia leaf spot on cotton cultivars sowed in two different times. The experiment was conducted in a triple factorial design (4x3x2), consisted of four cultivars, the three thirds of the plant and two sowing times, with four replications. Each plot was divided in two twin plots, one with fungicide application (with disease control) and the other without fungicide application (without disease control). The severity assessments were performed every seven days, considering each third of the plant with a diagrammatic scale. Yield was evaluated in each plot. There was a significant interaction between sowing times and the thirds of the plant in the plots without disease control for RLS severity, with the highest values of area under the disease progress curve (AUDPC) in the first sowing time (ST1) and in the lower third of the plant. The FMT705 cultivar had the highest and FM951LL the lowest value of AUDPC. The AUDPC of these cultivars were no statistically different in the second sowing time (ST2), but they had higher AUDPC values in the lower third. Highest yields were found with ST1 in plots with disease control, with no differences between the cultivars, however, lower yields were found in plots without disease control.

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