ABSTRACT Attempts to control Fusarium head blight (FHB) in wheat and barley ha ve mainly consisted of using resistant cultivars and/or spraying fungicides. The efficacy of chemical control depends on the potency of fungicides, time of application, and deposition on the infection sites. The objective of this study was to determine the relationship between presence of anthers and FHB. The e xperiment was conducted in the field in two sowing periods to assess anthesis duration, anther size, and infection in partially and fully exserted anthers . Incidence of FHB in spikes was not explained based only on the presence of partially exserted anthers in infected spikelets. Pampeano and CEP 00-59 were the least susceptible wheat cultivars, while CD 114 showed the highest incidence in spikes. Occurrence of FHB was, but not exclusively, related to anthesis duration, anther size, and presence of partially exserted anthers. All these factors may be involved in the infection of spikes.

RESUMO As tentativas de controle da giberela em trigo e cevada têm sido principalmente através da criação de cultivares resistentes e/ou pela aplicação de fungicidas. A eficiência do controle químico depende da potência do fungicida, do momento da aplicação e da deposição nos sítios infecção. O objetivo do trabalho foi determinar a relação da presença das anteras na infecção da giberela. O trabalho foi conduzido no campo em duas épocas de semeadura avaliando-se a duração da antese, o tamanho das anteras e a infecção em anteras parcialmente expostas e completamente expostas. A incidência da giberela em espigas não foi explicada unicamente pela presença de anteras parcialmente expostas em espiguetas infectadas. As cultivares de trigo Pampeano e CEP 00-59 foram as menos suscetíveis, enquanto a CD 114 apresentou a maior incidência em espigas. A ocorrência da giberela relacionou-se, mas não exclusivamente, com a duração da antese, tamanho de anteras e presença de anteras parcialmente expostas. Todos esses fatores podem estar envolvidos com a infecção das espigas.

Abstract. Since the start of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causing the coronavirus disease 2019 (COVID-19) pandemic, the concepts of serial and generation intervals have been used as key epidemiological measures to understand the transmission dynamics of the disease. We carefully examined and repurposed these concepts to the understanding of the transmission chain and dynamics of two major citrus diseases: tristeza virus (caused by Citrus tristeza virus, CTV) and Huanglongbing (caused by Candidatus Liberibacter asiaticus). Following the fundamental definition of the concepts, the review delineates the transmission chain in the SARS-CoV-2 and that of CTV and CLas, pointing out their major similarities and differences. Then, it discusses estimation of the serial and generation intervals and their distributions for both plant diseases. Identification of infector-infectee tree pairs in a transmission chain within orchards is proposed through use of disease incidence data from intensive mapping, spatial pattern analysis, conditional probability, and simulation approaches. Like in SARS-CoV-2 dynamics, pre-symptomatic transmission in these two plant pathosystems is of epidemiological significance. Hence, estimation of the serial and generation interval can lay the foundations to understanding of early disease transmission dynamics, thus the implementation of vector control measures or eradication of infected trees. We hope this review motivates discussions on estimation and usage of these concepts to enhance understanding of the epidemiology of both of the herein examined citrus diseases.

Resumen. Desde el inicio del síndrome respiratorio agudo grave del Coronavirus 2 (SARS-CoV-2) responsable de la pandemia COVID-19, los conceptos de intervalo serial e intervalo de generación se han usado como medidas epidemiológicas clave para entender la dinámica de transmisión de la enfermedad. En esta revisión, estos conceptos se han examinado y reorientado al entendimiento de la cadena de transmisión y dinámica de dos enfermedades importantes de los cítricos: la tristeza de los cítricos (causada por Citrus tristeza virus, CTV) y el Huanglongbing (causado por Candidatus Liberibaster asiaticus). Basados en la definición fundamental de los conceptos, la revisión define la cadena de transmisión del SARS-CoV-2 y del CTV y CLas, señalando sus mayores diferencias y similitudes. Posteriormente, la revisión discute el cálculo de los intervalos y sus distribuciones para ambas enfermedades. La identificación de pares de árboles infector-infectado en una cadena de transmisión dentro de huertos se propone a través del uso de datos de incidencia de enfermedad de mapeos intensivos, análisis de patrón espacial, probabilidad condicional y métodos de simulación. Al igual que en la dinámica del SARS-CoV-2, la transmisión pre-sintomática en estos dos patosistemas es de significancia epidemiológica. De ahí que el cálculo del intervalo serial y de generación puede ayudar a sentar las bases para el entendimiento de la dinámica de transmisión temprana, y con ello, la implementación de medidas de control del vector o la erradicación de árboles enfermos. Se espera que esta revisión motive discusiones sobre el cálculo y uso de estos conceptos para mejorar el entendimiento de la epidemiología de las enfermedades examinadas en este trabajo.

RESUMO A saúde das sementes é um dos fatores mais importantes que afetam a qualidade das sementes de grão-de-bico (Cicer arietinum). O presente estudo tem como objetivo comparar e identificar melhores métodos de incubação para a detecção de Ascochyta rabiei associada a sementes de grão-de-bico. Quatro protocolos foram comparados em sua sensibilidade para detectar A. rabiei: T1) Incubação em substrato de papel ou método do papel de filtro (“blotter test”) sem desinfecção superficial, T2) Botter test através da técnica de restrição de água, T3) Teste de placa com PDA e T4) Teste de placa com MEA. Quatro lotes de sementes de grão-de-bico independentes, naturalmente infectados com A. rabiei, foram amostrados na província de Córdoba e quatro na província de Buenos Aires, Argentina. No total, cada tratamento foi aplicado a um total de 400 sementes de cada localidade, para que os métodos sejam comparáveis. O T2 e T3 foram estatisticamente mais sensíveis para detectar sementes de Córdoba infectadas com A. rabiei. Apenas estes dois tratamentos foram repetidos com sementes da província de Buenos Aires, onde o T3 se mostrou mais sensível, por isso é recomendado para as rotinas de análise sanitária das sementes de grão-de-bico.

ABSTRACT Seed health is one of the most important factors affecting the quality of chickpea (Cicer arietinum) seeds. The present study aimed to compare and identify the best incubation methods for detecting Ascochyta rabiei associated with chickpea seeds. Four protocols were compared for their sensitivity in detecting A. rabiei: T1) Incubation on paper substrate or filter paper method (blotter test) without surface disinfection, T2) Blotter test through the water restriction technique, T3) PDA plate test, and T4) MEA plate test. Four independent chickpea seed lots, naturally infected with A. rabiei, were sampled from Córdoba Province and other four were sampled from Buenos Aires Province, Argentina. Each treatment was applied to a total of 400 seeds from each locality for the methods to be comparable. T2 and T3 were statistically more sensitive in detecting A. rabiei-infected seeds from Córdoba. Only these two treatments were repeated for seeds from Buenos Aires Province, and T3 proved to be more sensitive; thus, it is recommended for routine sanitary analysis of chickpea seeds.

RESUMO Pyricularia spp. é um complexo fúngico causamte da doença conhecida como brusone em mais de 50 espécies da família Poaceae. O mais conhecido é Pyricularia oryzae Cavara, patógeno em grandes culturas como arroz, trigo, milheto, cevada e plantas daninhas. Com o objetivo de atualizar a gama de hospedeiros, diferenciar os sintomas, isolar as cepas da região e caracterizá-las através do estudo morfométrico e cultural, foi realizado durante a campanha 2016/17, o levantamento de plantas com sintomas da doença em campos da província de Corrientes. O agente causal foi identificado por caracterização morfométrica e cultural como Pyricularia spp.

RESUMEN Pyricularia spp. es un complejo fúngico causante de la enfermedad conocida como tizón en más de 50 especies de la familia Poaceae. El más conocido es Pyricularia oryzae Cavara, patógeno en cultivos principales como arroz, trigo, mijo, cebada y malezas. Con el objetivo de actualizar el rango de hospedantes, diferenciar la sintomatología, aislar las cepas de la región y caracterizarlas a través del estudio morfométrico y cultural, se realizó durante la campaña 2016/17, el relevamiento de plantas con síntomas de tizón en campos de la provincia de Corrientes. El agente causal fue identificado por caracterización morfométrica y cultural como Pyricularia spp.

The detection of Porphyromonas gingivalis (P. gingivalis) was performed in adult patients with chronic periodontitis treated at the Clinic of Periodontology in the University of Antofagasta, through of microbiology techniques conventional and molecular biology. Were obtained samples of gingival crevicular fluid with paper cones (N 30) for 20 seconds of the more severe periodontal site in each quadrant, 37 patients were studied with chronic periodontitis, subsequent microbiological culture was performed on blood agar and the presence of P. gingivalis was detected through conventional microbiology techniques (fluorescence and stereomicroscope) and molecular biology technique (polymerase chain reaction). There was detected with stereomicroscope pigmented black in 75.7 % of the samples, of which 67.9 % were positive for P. gingivalis with the fluorescence technique. Through the polymerase chain reaction it was confirmed that 84.2 % of fluorescence positive colonies corresponded to P. gingivalis. In the population analyzed can conclude that there is a high prevalence of P. gingivalis in the subgingival microbiota of patients with chronic periodontitis which has been detected through techniques of conventional microbiology and by polymerase chain reaction. The smokers had a higher presence of P. gingivalis than nonsmokers.

Se realizó la detección de Porphyromonas gingivalis (P. gingivalis) en pacientes adultos con periodontitis crónica que se atendieron en la Clínica de Periodoncia de la Universidad de Antofagasta, a través de técnicas de microbiología convencional y técnica de biología molecular. fueron obtenidas muestras de fluido gingival crevicular de 37 pacientes con periodontitis crónica, con conos de papel (N 30) por 20 segundos del sitio periodontal más severo de cada cuadrante, posteriormente se realizó cultivo microbiológico en agar sangre y se detectó la presencia de P. gingivalis a través de técnicas de microbiología convencional (lupa estereoscópica y fluorescencia) y técnica de biología molecular (reacción en cadena de la polimerasa). se detectó con lupa estereoscópica colonias pigmentadas de negro en el 75,7 % de las muestras (n=28), de ellas el 67,9 % fueron positivas para P. gingivalis con la técnica de fluorescencia (n=19). A través de la reacción en cadena de la polimerasa se pudo confirmar que el 84,2 % de las colonias positivas por fluorescencia correspondían a P. gingivalis (n=16). En la población de estudio analizada es posible concluir que existe una alta prevalencia de P. gingivalis en la microbiota subgingival de los pacientes con periodontitis crónica lo que ha sido detectado a través de técnicas de microbiología convencional y mediante la reacción en cadena de la Polimerasa. Los pacientes fumadores presentaron mayor presencia de P. gingivalis que los no fumadores.

The aim of this study was to evaluate in vitro the mycelial susceptibility of Trichoconiella padwickii to different active ingredients through average median concentration IC50 calculation. Inoculum disks were seeded on bean agar at different concentrations (0.1; 1; 10; 30, 50; 100 and 1000 mg/l) of various fungicides. After seven days the colony diameter was measured. The data obtained were fitted to nonlinear regression models. Susceptibility was classified using the scale proposed by Edgington. The results show that the pathogen is very sensitive to products that act on the respiratory chain (quinone outside inhibitors QoI and succinate dehydrogenase inhibitors SDHI) and cell membrane (multi-site contact activity), and moderately sensitive to those products interfering with cell division (methyl benzimidazole carbamates MBC), synthesis of nucleic acids (phenylamides PA) and osmotic signal transduction (multi-site contact activity). This work is the first record on the sensitivity of T. padwickii.

El objetivo de este trabajo fue evaluar in vitro la sensibilidad micelial de Trichoconiella padwickii a diferentes principios activos por medio del cálculo de la concentración inhibitoria media (CI50). Para ello se realizaron siembras de discos de inóculo en agar poroto con distintas concentraciones (0,1; 1; 10; 30, 50; 100 y 1.000 mg/l) de diversos fungicidas. A los 7 días se midió el diámetro de crecimiento de la colonia (cm). Los datos obtenidos se ajustaron a modelos de regresión no lineal. La sensibilidad se clasificó utilizando la escala de Edgington. Los resultados obtenidos demuestran que el patógeno es muy sensible a los productos que actúan sobre la cadena respiratoria (quinone outside inhibitors QoI y succinate dehydrogenase inhibitors SDHI) y la membrana celular (multisitio), y moderadamente sensible a los que interfieren en la división celular (metil benzimidazol carbamatos MBC), en la síntesis de ácidos nucleicos (fenilamidas PA) y en la transducción de la señal osmótica (actividad multisitio). Este trabajo es el primer antecedente sobre la sensibilidad in vitro de T. padwickii a principios activos fungicidas.

Analisou-se trabalhos publicados contendo valores da concentração de um fungicida que controla 50% (CI50) um dado fungo. Na análise considerou-se: (i) a CI50 determinada in vitroe in vivopara um dado fungicida e para um fungo específico; (ii) a concentração (g/ha) de ingrediente ativo do fungicida indicada para o controle da doença alvo no campo; (iii) volume de água de 120/L usado na pulverização; (iv) a concentração (mg/L) de i.a. dos fungicidas nesse volume (120 L/ha); (v) e determinou-se a relação da concentração usada no campo com a determinada no laboratório. As análises foram feitas com dados da CI50de fungicidas IDMs, IQes, um carbamato e um benzimidazol e com os seguintes fungos: Bipolaris sorokiniana, Drechslera tritici-repentis, D. siccans, Fusarium graminearume Puccinia triticina, Exserohilum turcicum, Phakopsora pachyrhizie Corynespora cassiicola. A concentração do fungicida na calda pulverizada no campo variou de 33,9 (D. siccanse trifloxistrobina) a 500.000,0 (E. turcicume iprodiona) vezes superior a determinada em laboratório. Concluiu-se que a CI50 não teve relação com a concentração usada no campo e por isso deve ser usada na comparação da potência entre fungicidas e no monitoramento da sensibilidade de fungos.

Published data containing fungicide concentrations that control 50% (IC50) of a given fungus were analyzed. In the analysis we considered: (i) the IC50 determined in vitroand in vivofor a given fungicide and for a specific fungus; (ii) the concentration (g/ha) of active ingredient for the fungicide indicated to control a specific disease in the field; (iii) water volume of 120/L used in the spray; (iv) the fungicide a.i. concentration (mg/L) in 120 L volume; (v) and the ratio of the concentration used in the field with that determined in the laboratory. The analysis were performed by using IC50 data for DMIs, QoIs, a carbamate and a benzimidazol against the following fungi Bipolaris sorokiniana, Drechslera tritici-repentis, D. siccans, Fusarium graminearum, Puccinia triticina, Exserohilum turcicum, Phakopsora pachyrhiziand Corynespora cassiicola. The fungicide concentrations sprayed in the field were 33.9 (D. siccansand trifloxystrobin) to 500,000.0 (E. turcicumand iprodione) times higher than that determined in the laboratory. It was concluded that the IC50 was not related to the concentration used in the field and therefore should be used to compare the power among fungicides and to monitor the fungal sensitivity shift towards fungicides

O objetivo deste trabalho foi determinar as condições mínimas de duração do molhamento em função da temperatura requeridas para a infecção de giberela em trigo. O modelo climático desenvolvido por Zoldan (2008) foi testado em experimentos de campo com duas cultivares de trigo cultivadas em 2005 (cinco épocas de semeadura) e 2006 (seis épocas de semeadura) em parcelas de 10 m² com três repetições. A doença foi avaliada pela incidência em espigas (IE), incidência em espiguetas (Ie) e pela interação desses dois métodos e considerado como severidade. A partir do início da antese, a temperatura do ar e a duração do molhamento das espigas foram monitorados diariamente com uma estação meteorológica automática. Com a combinação desses dois fatores, foi elaborada uma tabela de favorabilidade do ambiente para ocorrência da doença. A partir do dia do início da floração (1-5% anteras completamente expostas) a soma dos valores diários para favorabilidade para a infecção (SVDFI) foi calculada com um programa de computador, de acordo com a tabela de Zoldan (2008). Os sintomas iniciais da doença foram observados com uma incidência em espigas de 3,7% e correspondendo 2,6 de SVDFI. A infecção do trigo ocorre em função de chuvas que resultam no molhamento das espigas > 61.4 h de duração. A previsão da ocorrência de chuvas pode auxiliar na indicação do momento indicador da aplicação de fungicidas visando ao controle da giberela. Propõem-se o nome do sistema de aviso de UPF-scab-alert.

The aim of this study was to determine the minimum conditions of wetness duration and mean temperature required for Fusarium head blight infection in wheat. The weather model developed by Zoldan (2008) was tested in field experiments for two wheat cultivars grown in 2005 (five sowing dates) and 2006 (six sowing dates) in 10 m² plots with three replicates. The disease was assessed according to head incidence (HI), spikelet incidence (SI), and the interaction between these two methods was called head blight severity (HBS). Starting at the beginning of anthesis, air temperature and head wetness duration were daily recorded with an automatic weather station. With the combination of these two factors, a weather favorability table was built for the disease occurrence. Starting on the day of flowering beginning (1 - 5% fully exserted anthers), the sum of daily values for infection favorability (SDVIF) was calculated by means of a computer program, according to Zoldan (2008) table. The initial symptoms of the disease were observed at 3.7% spikelet incidence, corresponding to 2.6 SVDFI. The infection occurs in wheat due to rainfall which results in spike wetting of > 61.4 h duration. Rainfall events forecast can help time fungicide application to control FHB. The name of this alert system is proposed as UPF-scab alert.

With the objective of quantifying the transmission efficiency (TE) from rice seed to coleoptiles, a trial was conducted "in vivo" using seeds of the varieties BRS Taim, Puitá Inta-CL and Irga 424. Seeds were sown in plastic trays containing sterile sand as substrate and incubated in laboratory conditions at 25±2ºC and photoperiod of 12 h. The TE was evaluated after seven days using 400 coleoptiles put on agarbean medium 3%. The TE was 7%, 28.5% and 8.1% for varieties BRS Taim, Puitá Inta-CL and Irga 424, respectively, demonstrating the importance of seeds as an inoculum source of T. padwickii.

El hongo Trichoconiella padwickii es uno de los principales patógenos de la semilla de arroz en la provincia de Corrientes, Argentina. Con el objetivo de cuantificar la eficiencia de transmisión (ET) desde la semilla a coleóptilos de arroz se realizó un ensayo "in vivo", utilizando semillas de las variedades BRS Taim, Puitá Inta-CL e Irga 424. Las semillas se sembraron en bandejas plásticas conteniendo arena estéril como sustrato e incubadas en laboratorio en condiciones de 25 ± 2ºC y fotoperiodo de 12 h. La ET se evaluó a los siete días, sobre 400 coleóptilos sembrados en medio agar poroto 3%. El patógeno presentó los siguientes valores de ET: 7% para la variedad BRS Taim; 28,5% en Puitá Inta-CL y 8,1% en la variedad Irga 424. Se demostró la importancia de la semilla como fuente de inóculo de T. padwickii.

The main objectives of this work were to isolate and identify the causal agents of sudden death syndrome (SDS) from samples collected in different Argentinean localities, to quantify its incidence, and to estimate yield losses. Two hundred and fifteen roots from plants with typical SDS foliar symptoms were analyzed. In order to perform pathogenicity tests, two bioassays were conducted in the greenhouse. Yield losses were estimated in a field trial located in Pergamino by quantification and comparison of yield of paired samples. Thirty-six percent of total roots (78 roots) presented signs of Fusarium, compatible with signs caused by SDS. Morphological studies allowed the identification of 35 isolates as F. tucumaniae and 18 as F. virguliforme. Other eight isolates could not be identified. All isolates that were inoculated reproduced typical SDS foliar symptoms. Significant differences were observed between healthy and diseased plants for 1000-grain weight and between potential and real yield (p<0.05). Average yield loss was 1514 kg/ha (range 192-3770 kg/ha). These results corroborated the distribution and predominance of F. tucumaniae and F. viguliforme in the area under study and its destructive potential.

Los objetivos de este trabajo fueron aislar e identificar los agentes causales del síndrome de la muerte súbita (SMS) en muestras provenientes de diferentes localidades de Argentina, y cuantificar la incidencia de la enfermedad y los daños causados a campo en el rendimiento. Se analizaron 215 raíces provenientes de plantas con síntoma foliares típicos de SMS para el aislamiento e identificación de los agentes causales. Para realizar las pruebas de patogenicidad se efectuaron dos bioensayos en invernáculo. Los daños fueron estimados en un ensayo a campo situado en Pergamino a través de la cuantificación del rendimiento de muestras apareadas. El 36% (78 raíces) de las raíces presentó signos de Fusarium, compatibles con los causantes de SMS. Los estudios morfológicos realizados permitieron identificar 35 aislamientos como F. tucumaniae y 18, como F. virguliforme. Otros ocho aislamientos no pudieron identificarse. Todos los aislamientos inoculados reprodujeron los síntomas foliares típicos de SMS. Se observaron diferencias entre el peso de mil granos de plantas sanas y de plantas enfermas y entre el rendimiento potencial y el real (p<0,05). Los daños promedio fueron de 1514 kg/ha (rango 192-3770 kg/ha). Los resultados obtenidos corroboraron la distribución y predominio de F. tucumaniae y F. viguliforme en el área estudiada y su potencial destructivo.

Disease severity evaluation is an important decision support for adoption of strategies and tactics for disease control. The most commonly used method to assess disease severity is visual, but the problem is repeatability, due to subjectivity and imprecision of estimates. For Puccinia sorghi, a threshold of action of 1% severity was determined, so high precision is required in disease quantification. The aim of this study was to compare different assessment methods and analyze their association. Two diagrammatic scales were used to estimate severity, the Peterson and Amorim scales. Pustules were counted with the naked eye and with a 20x magnification hand lens. Software for disease quantification, Assess 2.0, was used to determine actual percentage area and lesion count. No significant differences were found between naked-eyed count and with magnifier. Lesion count with Assess 2.0 gave an imprecise result. Significant differences were found between diagrammatic scales. Compared with Assess 2.0, severity using Peterson was 2% higher, showing widely scattered differences (R²=0.48). Overestimation with visual scales was suggested, especially at low severity levels. Counting pustules was more objective, precise and reproducible. Thus, a calibration curve was constructed (R²=0.79), which will allow calculation of severity from counting pustules.

Widely spread in Argentina, late season diseases (LSD), cause yield losses and seed quality changes. Leaf application of fungicides is an effective procedure to manage LSD under the current cropping conditions (monocrop and no-till system). The aims of the present study were 1) to determine causal agents of LSD, 2) to evaluate yield reduction caused by LSD and 3) to evaluate the efficiency of mixtures containing triazoles and strobirulins, sprayed during R3 or R5 reproductive stages to control LSD. Four experiments were carried out in a randomized complete block design, with four replicates in Armstrong, Santa Fe, Argentina, in a soybean cultivation area in the Pampeana Region. Two assays were performed in 2004/2005, and the remaining ones in 2005/2006 growing seasons. Two azoxystrobin mixtures, one with cyproconazole and the other with difenoconazole, and a mixture of the latter two were tested. The following pathogens were detected : Cercospora kikuchii, Colletotrichum truncatum, Septoria glycines, Glomerella glycines y Phomopsis sojae. All treatments presented higher yield than control, with 5% of statistic significance. It can be concluded that, under the present experimental conditions, characterized by frequent rains between R1 and R5.5, the tested mixtures efficiently controlled LSD.

Las enfermedades de fin de ciclo de la soja (EFC), ampliamente difundidas en Argentina, afectan el rendimiento del cultivo y la calidad de la semilla cosechada. La aplicación foliar de fungicidas representa una alternativa eficiente en las actuales condiciones de cultivo (monocultivo y siembra directa). Los objetivos del presente trabajo fueron 1) determinar los agentes causales de la EFC presentes en los ensayos, 2) evaluar la disminución de rendimiento causada por las EFC y 3) valorar la eficiencia de control de mezclas de triazoles y azoxistrobina aplicados en las etapas reproductivas R3 o R5, para el control de las mismas. Se realizaron cuatro ensayos, dos en la campaña 2004/2005, y dos en la campaña 2005/2006, en Armstrong, Santa Fe, núcleo del área sojera de la Región Pampeana. Se utilizaron dos mezclas de azoxistrobina, una con cyproconazole y otra con difenoconazole, y una mezcla de los dos últimos. Los patógenos detectados fueron: Cercospora kikuchii, Colletotrichum truncatum, Septoria glycines, Glomerella glycines y Phomopsis sojae. Todos los tratamientos tuvieron mayores rendimientos que el control no tratado en todos los ensayos, con un nivel de significancia del 5%. Se concluye que, bajo las condiciones de los ensayos, con altas precipitaciones entre R1 y R5.5, los productos utilizados, controlaron eficientemente las EFC presentes.

From 2003 to 2008, late season disease severity (LSDsev) values (Brown spot and Cercospora leaf blight) were recorded at the R7 growth stage at several sites in Santa Fe and Córdoba Provinces. The annual LSDsev records (N=15) were grouped into two epidemic categories based on a threshold value (median of observed disease data): severe (LSDsev >36 %) and moderate to light (LSDsev <=36 %). Variations in epidemic levels were studied in relation to precipitation-based variables, processed in a time window limited by R3 and R5 growth stages. The variables were expressed as frequency (days) and total accumulation (mm) of daily precipitations greater than the thresholds 1, 5, 7 and 10 mm. The variables PrF7 (number of days with precipitations>7 mm) and AcPr7 (total accumulation of daily precipitations >7 mm) and the interaction (product) between them (It7) were the most strongly correlated, according to Kendall tau-b coefficients (rK=0.74, 0.60 and 0.71 respectively). Logistic regression model including AcPr7 correctly estimated the probability of occurrence of epidemic categories in 12 cases (out of 15). Logistic models integrating PrF7 or the interaction effect (It7) presented prediction accuracies of 93.3 %. These results could be useful for prediction and chemical control of LSD.

Durante los años 2003 a 2008 se evaluó la severidad de las enfermedades de fin de ciclo (SevEFC, mancha marrón y tizón morado) en el estado fenológico R7 en localidades de las provincias de Santa Fe y Córdoba. Los valores de SevEFC (N=15) se categorizaron binariamente en función de un valor umbral en: epidemia severa (Sev EFC>36 %) y epidemia moderada a ligera (<=36 %). La variación de la SevEFC en R7 fue analizada en relación a variables ligadas a la precipitación, procesadas entre R3 y R5. Las variables se expresaron como frecuencia y precipitación acumulada en mm, que superan los umbrales: 1, 5, 7 y 10 mm. Las variables DPr7 (días con precipitación >7 mm), PrAc7 (acumulado de precipitaciones diarias >7 mm) y la interacción entre ambas (It7) resultaron ser las más fuertemente correlacionadas con los niveles epidémicos (coeficiente de Kendall Tau-b (r K = 0,74, 0,60 y 0,71 respectivamente). El modelo de regresión logística que incluyó a PrAc7 estimó correctamente la probabilidad de ocurrencia en 12 de las 15 observaciones de SevEFC. Los modelos logísticos que integraron las variables DPr7 o It7, obtuvieron precisiones de predicción de 93,3 %. Estos resultados podrían ser útiles para la predicción y control de las EFC.