Effects of temperature and leaf wetness duration on infection of pear leaves by Venturia pirina

2000 ◽  
Vol 51 (1) ◽  
pp. 97 ◽  
Author(s):  
O. N. Villalta ◽  
W. S. Washington ◽  
G. M. Rimmington ◽  
P. A. Taylor
Keyword(s):  
Disease Severity ◽  
Field Experiments ◽  
Leaf Wetness ◽  
Leaf Wetness Duration ◽  
Controlled Conditions ◽  
Pyrus Communis L ◽  
Venturia Pirina ◽  
Effects Of Temperature ◽  
Relationship Of ◽  
The Relationship

The effects of temperature and wetness duration on the infection of pear leaves (Pyrus communis L.) by Venturia pirina were studied by inoculating plants with ascospores and conidia under controlled conditions and in the field. Under controlled inoculations, minimum wetness durations that lead to leaf infections by ascospores were 27, 15, 13, 11, 10, 9, and 9 h at 4, 8, 10, 12, 15, 20, and 25°C, respectively. In parallel inoculations with conidia, the minimum wetness durations that lead to leaf infections were similar to ascospores at temperatures between 12°C and 25°C, but at lower temperatures (4, 8, 10°C), conidia infected leaves only after an additional 2 h of leaf wetness. The relationship between minimum wetness times and temperature was best described using an exponential regression. In field experiments, leaf infection on plants inoculated with ascospores and conidia under various naturally occurring wetness and temperature conditions was in close agreement with those under controlled conditions. Disease severity (percent of leaf area infected) increased with increasing leaf wetness duration at all temperatures. The optimum temperature for infection was 20°C. Analysis of variance with orthogonal polynomial contrasts was used to define the relationship of the angular transformation of disease severity to temperature and leaf wetness duration.

scholarly journals Interactive Effects of Temperature and Leaf Wetness Duration on Sporangia Germination and Infection of Cucurbit Hosts by Pseudoperonospora cubensis

Plant Disease ◽  
2012 ◽  
Vol 96 (3) ◽  
pp. 345-353 ◽  
Author(s):  
K. N. Neufeld ◽  
P. S. Ojiambo
Keyword(s):  
Leaf Area ◽  
Downy Mildew ◽  
Disease Severity ◽  
Leaf Wetness ◽  
Pseudoperonospora Cubensis ◽  
Weibull Function ◽  
Leaf Wetness Duration ◽  
Cucurbit Downy Mildew ◽  
Host Type ◽  
Effects Of Temperature

Outbreaks of cucurbit downy mildew caused by Pseudoperonospora cubensis are dependent on the weather but effects of temperature and leaf wetness duration on infection have not been studied for different cucurbits. To determine the effects of these two weather variables on sporangia germination and infection of cucurbit host types by P. cubensis, three host types; cucumber (‘Straight 8’), cantaloupe (‘Kermit’), and acorn squash (‘Table Queen’), were inoculated and exposed to leaf wetness durations of 2 to 24 h at six constant temperatures ranging from 5 to 30°C in growth-chamber experiments. Sporangia germination was assessed after each wetness period, and leaf area infected was assessed 5 and 7 days after inoculation. Germination of sporangia was highest on cantaloupe (16.5 to 85.7%) and lowest on squash (10.7 to 68.9%), while disease severity was highest and lowest on cucumber and cantaloupe, respectively. Host type, temperature, wetness duration and their interactions significantly (P < 0.0001) affected germination and disease severity. Germination and disease data for each host type were separately fitted to a modified form of a Weibull function that characterizes a unimodal response and monotonic increase of germination or infection with temperature and wetness duration, respectively. The effect of host type on germination and infection was characterized primarily by differences in the upper limit parameter in response to temperature. Differences among host types based on other parameters were either small or inconsistent. Temperature and wetness duration that supported a given level of germination or infection varied among host types. At 20°C, 15% leaf area infected was expected following 2, 4, and 8 h of wetness for cucumber, squash, and cantaloupe, respectively. When temperature was increased to 25°C, 15% disease severity was expected following 3, 7, and 15 h of wetness for cucumber, squash, and cantaloupe, respectively. Risk charts were constructed to estimate the potential risk of infection of cucurbit host types by P. cubensis based on prevailing or forecasted temperature and leaf wetness duration. These results will improve the timing and application of the initial fungicide spray for the control of cucurbit downy mildew.

scholarly journals Weather based warning systems for bean angular-leaf-spot and anthracnose

2012 ◽  
Vol 38 (3) ◽  
pp. 228-231
Author(s):  
Erlei Melo Reis ◽  
Marta Maria Casa Blum
Keyword(s):  
Disease Severity ◽  
Leaf Spot ◽  
Field Experiments ◽  
Electronic Device ◽  
Natural Infection ◽  
Colletotrichum Lindemuthianum ◽  
Angular Leaf Spot ◽  
Leaf Wetness ◽  
Phaeoisariopsis Griseola ◽  
Leaf Wetness Duration

Data available in the literature were used to develop a warning system for bean angular leaf spot and anthracnose, caused by Phaeoisariopsis griseola and Colletotrichum lindemuthianum, respectively. The model is based on favorable environmental conditions for the infectious process such as continuous leaf wetness duration and mean air temperature during this subphase of the pathogen-host relationship cycle. Equations published by DALLA PRIA (1977) showing the interactions of those two factors on the disease severity were used. Excell spreadsheet was used to calculate the leaf wetness period needed to cause different infection probabilities at different temperature ranges. These data were employed to elaborate critical period tables used to program a computerized electronic device that records leaf wetness duration and mean temperature and automatically shows the daily disease severity value (DDSV) for each disease. The model should be validated in field experiments under natural infection for which the daily disease severity sum (DDSS) should be identified as a criterion to indicate the beginning and the interval of fungicide applications to control both diseases.

scholarly journals A Model Defining the Relationship Between Temperature and Leaf Wetness Duration, and Infection of Watermelon by Colletotrichum orbiculare

Plant Disease ◽  
1997 ◽  
Vol 81 (7) ◽  
pp. 739-742 ◽  
Author(s):  
J. S. Monroe ◽  
J. B. Santini ◽  
R. Latin
Keyword(s):  
Experimental Design ◽  
Orthogonal Polynomial ◽  
Analysis Of Variance ◽  
Leaf Wetness ◽  
Controlled Environment ◽  
Optimum Temperature ◽  
Colletotrichum Orbiculare ◽  
Leaf Wetness Duration ◽  
Relationship Of ◽  
The Relationship

Controlled environment experiments were conducted to determine the relationship between temperature, leaf wetness duration, and infection of watermelon by Colletotrichum orbiculare. Flats of watermelon seedlings were inoculated and exposed to various combinations of temperature (12, 15, 18, 21, 24, 27, and 30°C) and leaf wetness duration (2, 4, 8, 12, 16, and 24 h). The experimental design was a split-plot, with whole units represented by temperature and subunits represented by leaf wetness duration. Anthracnose incidence, defined as the percentage of symptomatic seedlings in each flat 10 days after inoculation, increased with increasing leaf wetness duration at all levels of temperature. The optimum temperature for infection ranged from 21 to 24°C. At most temperatures, as little as 2 h of leaf wetness was required for infection. Analysis of variance with orthogonal polynomial contrasts and multiple regression procedures was used to define the relationship of anthracnose incidence to temperature and leaf wetness duration.

scholarly journals Epidemiology of apple leaf spot

2002 ◽  
Vol 27 (1) ◽  
pp. 65-70 ◽  
Author(s):  
LUCIANO U. CRUSIUS ◽  
CARLOS A. FORCELINI ◽  
ROSA M.V. SANHUEZA ◽  
JOSÉ M.C. FERNANDES
Keyword(s):  
Disease Severity ◽  
Leaf Spot ◽  
Leaf Wetness ◽  
Rio Grande Do Sul ◽  
Forecast System ◽  
Initial Inoculum ◽  
Growing Seasons ◽  
Colletotrichum Spp ◽  
Relationship Of ◽  
The Relationship

Apple leaf spot (ALS) caused by Colletotrichum spp. is a major disease of apple (Malus domestica) in Southern Brazil. The epidemiology of this disease was studied in experiments carried out in the counties of Passo Fundo and Vacaria, State of Rio Grande do Sul, from February 1998 to October 2000. The disease was found in all the six apple orchards sampled in the growing seasons of 1997/98 and 1998/99. The fungus isolates associated with ALS fit the characteristics of C. gloeosporioides (75%), C. acutatum (8%), and Colletotrichum sp. (17%). The pathogen overwintered in dormant buds and twigs but not in dropped leaves or fruit mummies. Two sprays of copper oxychloride (at 0.3%) reduced the fungus initial inoculum by 65-84.6% in buds and 85.6-93.7% in twigs, but had no effect on the early season progress of the disease. Disease severity increased proportionally to elevation of temperature from 14 to 26-28 °C. At 34 °C, however, infection was completely inhibited. The duration of leaf wetness required for infection ranged from two hours at 30 °C to 32 h at 16 °C. The relationship of temperature (T) and leaf wetness (W) to disease severity (Y) was represented by the model equation Y = 0.00145[((T-13)1.78)((34.01-T )1.09)] * 25/[1+14 exp(-0.137W)], R² = 0.73 and P < 0.0001. Currently, this information is being used to manage the disease and to validate a forecast system for ALS.

scholarly journals Interactions Between Chill-Hours and Degree-Days Affect Carpogenic Germination in Monilinia vaccinii-corymbosi

2001 ◽  
Vol 91 (1) ◽  
pp. 77-83 ◽  
Author(s):  
H. Scherm ◽  
A. T. Savelle ◽  
P. L. Pusey
Keyword(s):  
Laboratory Experiments ◽  
Field Experiments ◽  
Degree Days ◽  
Carpogenic Germination ◽  
Conditioning Period ◽  
Low Degree ◽  
Heating Degree Days ◽  
Relationship Of ◽  
High Degree ◽  
The Relationship

The relationship of cumulative chill-hours (hours with a mean temperature <7.2°C) and heating degree-days (base 7.2°C) to carpogenic germination of pseudosclerotia of Monilinia vaccinii-corymbosi, which causes mummy berry disease of blueberry, was investigated. In two laboratory experiments, pseudosclerotia collected from rabbiteye blueberry in Georgia were conditioned at 5 to 6°C for 26 to 1,378 h prior to placement in conditions favorable for germination and apothecium development. The number of chill-hours accumulated during the conditioning period affected the subsequent proportion of pseudosclerotia that germinated and produced apothecia, with the greatest incidence of carpogenic germination occurring after intermediate levels of chilling (≈700 chill-hours). The minimum chilling requirement for germination and apothecium production was considerably lower than that reported previously for pseudo-sclerotia from highbush blueberry in northern production regions. The rate of carpogenic germination was strongly affected by interactions between the accumulation of chill-hours and degree-days during the conditioning and germination periods; pseudosclerotia exposed to prolonged chilling periods, once transferred to suitable conditions, germinated and produced apothecia more rapidly (after fewer degree-days had accumulated) than those exposed to shorter chilling periods. Thus, pseudosclerotia of M. vaccinii-corymbosi are adapted to germinate carpogenically following cold winters (high chill-hours, low degree-days) as well as warm winters (low chill-hours, high degree-days). Results were validated in a combined field-laboratory experiment in which pseudosclerotia that had received various levels of natural chilling were allowed to germinate in controlled conditions in the laboratory, and in two field experiments in which pseudosclerotia were exposed to natural chilling and germination conditions. A simple model describing the timing of apothecium emergence in relation to cumulative chill-hours and degree-days was developed based on the experiments. The model should be useful for better timing of field scouting programs for apothecia to aid in management of primary infection by M. vaccinii-corymbosi.

scholarly journals Influence of Leaf Wetness Duration and Temperature on Infection of Grape Leaves by Elsinoë ampelina under Controlled and Vineyard Conditions

Plant Disease ◽  
2020 ◽  
Vol 104 (11) ◽  
pp. 2817-2822
Author(s):  
Odile Carisse ◽  
Audrey Levasseur ◽  
Caroline Provost
Keyword(s):  
Leaf Area ◽  
Weather Conditions ◽  
Leaf Wetness ◽  
Predictive Capacity ◽  
Leaf Wetness Duration ◽  
Infection Period ◽  
Richards Model ◽  
Elsinoe Ampelina ◽  
Independent Observations ◽  
The Relationship

On susceptible varieties, indirect damage to vines infected by Elsinoë ampelina range from reduced vigor to complete defoliation while, on berries, damage ranges from reduced quality to complete yield loss. Limited knowledge about the relationship between weather conditions and infection makes anthracnose management difficult and favors routine application of fungicides. The influence of leaf wetness duration and temperature on infection of grape leaves by E. ampelina was studied under both controlled and vineyard conditions. For the controlled conditions experiments, the five youngest leaves of potted vines (Vidal) were inoculated with a conidia suspension and exposed to combinations of six leaf wetness durations (from 0 to 24 h) and six constant temperatures (from 5 to 30°C). A week after each preset infection period, the percent leaf area diseased (PLAD) was assessed. At 5°C, regardless of the leaf wetness duration, no disease developed. At 10 and at 15 to 30°C, the minimum leaf wetness durations were 4 and 6 h, respectively. Above the minimum wetness duration, at temperatures from 10 to 30°C, PLAD increased linearly, with increasing leaf wetness up to 12 h, and then at a lower rate from 12 to 24 h. The optimal temperature for infection was 25°C. Relative infection was modeled as a function of both temperature and wetness duration using a Richards model (R2 = 0.93). The predictive capacity of the model was evaluated with data collected in experimental vineyard plots exposed to natural wetness durations or artificial wetness durations created using sprinklers. In total, 264 vineyard infection events were used to validate the controlled experiments model. There was a linear relationship between the risk of infection estimated with the model and the observed severity of anthracnose (R2 = 90); however, the model underestimated disease severity. A risk chart was constructed using the model corrected for vineyard observations and three levels of risk, with light, moderate, and severe risks corresponding to ≤5, >5% to ≤25, and >25% leaf area diseased, respectively. Overall, 93.9% of 132 independent observations were correctly classified, with 100, 29.4, and 9.4% of the light, moderate, and severe risks, respectively.

scholarly journals Bremia lactucae Infection Efficiency in Lettuce is Modulated by Temperature and Leaf Wetness Duration Under Quebec Field Conditions

Plant Disease ◽  
2015 ◽  
Vol 99 (7) ◽  
pp. 1010-1019 ◽  
Author(s):  
M. L. Fall ◽  
H. Van der Heyden ◽  
C. Beaulieu ◽  
O. Carisse
Keyword(s):  
Downy Mildew ◽  
Field Experiments ◽  
Field Conditions ◽  
Risk Indicators ◽  
Growth Chamber ◽  
Leaf Wetness ◽  
Risk Indicator ◽  
Bremia Lactucae ◽  
Infection Efficiency ◽  
Leaf Wetness Duration

More than 80% of Canadian lettuce production is located in the province of Quebec. Yet most of our knowledge on the epidemiology of lettuce downy mildew (Bremia lactucae) is derived from controlled-condition experiments or field experiments conducted in subtropical climates and, thus, cannot readily be applied to Quebec lettuce production. The influence of temperature and leaf wetness duration on the infection efficiency (IE) of B. lactucae was studied for 4 years (2003, 2004, 2012, and 2013) under field and growth-chamber conditions. IE was defined as the ratio of the number of lesions/leaf to the airborne conidia concentration (ACC). B. lactucae ACC was measured with rotating-arm samplers three times/week. In addition, 72 lettuce trap plants/sampling day were exposed to the potential airborne B. lactucae inoculum and disease intensity was assessed after 7 days of incubation in greenhouse. Under growth-chamber conditions, an ACC of 1 conidium/m3 was sufficient to cause 1 lesion/leaf, and IE ranged from 0.25 to 1.00. Under field conditions, an ACC of 10 to 14 conidia/m3 was required to cause 1 lesion/leaf, and IE ranged from 0.02 to 0.10, except in 2004, when IE ranged from 0.03 to 1.00. IE increased with increasing leaf wetness duration but decreased with increasing temperature. Also, considering an observed average temperature range from 10 to 20°C in the area of Quebec, 2 h of leaf wetness was sufficient for infection by B. lactucae. Therefore, under Quebec lettuce production conditions, a leaf wetness period of 2 h and an ACC of 10 to 14 conidia/m3 can be used as risk indicators to facilitate disease management decisions. Also, under typical Quebec weather conditions, measuring both morning and evening leaf wetness events could be used to improve the reliability of leaf wetness duration as a downy mildew risk indicator. Further research is needed to validate these risk indicators for integration into management strategies.

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