Temperature Influence on Pseudothecia Development Stages of Venturia inaequalis in the Western Cape of South Africa

Pseudothecia development stages of Venturia inaequalis (apple scab) were investigated in two climatically different regions in the Western Cape of South Africa. The aim was to determine the pseudothecial density (PD; pseudothecia per fertile lesion [p/f]) and ascal density (AD; asci per pseudothecium [a/p]) that contributes to defining the potential ascospore dose in a common prediction model of the apple scab infection risk. The PD and AD were compared between Elgin (EL), now considered a warm winter apple-growing region because of climate warming, and Koue Bokkeveld (KB), a cold winter region. In 2012 and 2013, scabbed apple leaves were collected during leaf-drop in KB and EL and overwintered either in their region of origin or in the other region. PD was significantly higher in scabbed leaves collected and overwintered in KB (mean, 24.11 p/f) than in leaves collected in KB and overwintered in EL (mean, 17.11 p/f; P < 0.001). PD of scabbed leaves collected and overwintered in EL (mean, 15.27 p/f) or collected in EL and overwintered in KB (mean, 16.07 p/f) did not differ significantly. Ascal density did not differ significantly in any treatment or season. We concluded that the significantly higher PD of scabbed leaves collected from the cooler region of KB and overwintered in KB compared with scabbed leaves collected in EL or KB and overwintered in EL could be caused by adaptations of V. inaequalis populations to the respective climates. This implied long-term effects of climate warming on apple scab epidemiology and management.

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A Decade Plus of Monoculture Wheat Compared to Wheat/Legume Pastures – Long-term Effects of Management Practices on Some Soil Physicochemical and Microbial Properties in the Winter Rainfall Region of South Africa

International Research in Environment, Geography and Earth Science Vol. 8 ◽

10.9734/bpi/ireges/v8/6243d ◽

2021 ◽

pp. 144-161

Author(s):

A. Marais ◽

M. Booyse ◽

A. Botha

Keyword(s):

South Africa ◽

Management Practices ◽

Long Term Effects ◽

Winter Rainfall ◽

Microbial Properties ◽

Rainfall Region

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The long-term effects of fire regime on primary production of montane grasslands in South Africa

African Journal of Range and Forage Science ◽

10.2989/10220119.2015.1124922 ◽

2016 ◽

Vol 33 (1) ◽

pp. 33-41 ◽

Cited By ~ 14

Author(s):

Colin S Everson ◽

Terry Everson

Keyword(s):

South Africa ◽

Primary Production ◽

Fire Regime ◽

Long Term Effects ◽

Montane Grasslands

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A Link of Full-Scale Accelerated Pavement Testing to Long-Term Pavement Performance Study in the Western Cape Province of South Africa

The Roles of Accelerated Pavement Testing in Pavement Sustainability ◽

10.1007/978-3-319-42797-3_5 ◽

2016 ◽

pp. 67-79 ◽

Cited By ~ 1

Author(s):

J. K. Anochie-Boateng ◽

W. JvdM Steyn ◽

C. Fisher ◽

L. Truter

Keyword(s):

South Africa ◽

Full Scale ◽

Pavement Performance ◽

Western Cape ◽

Performance Study ◽

Western Cape Province ◽

Accelerated Pavement Testing ◽

Pavement Testing

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Long-term trends, seasonal abundance and energy consumption of waterbirds at Rietvlei, Western Cape, South Africa, 1950–1997

Ostrich ◽

10.2989/00306520109485289 ◽

2001 ◽

Vol 72 (1-2) ◽

pp. 63-79 ◽

Cited By ~ 2

Author(s):

B. Kalejta-Summers ◽

D.G. Allan ◽

T.D. Longrigg

Keyword(s):

South Africa ◽

Energy Consumption ◽

Seasonal Abundance ◽

Western Cape ◽

Long Term Trends

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Identification of Resistance to Multiple Fungicides in Field Populations of Venturia inaequalis

Plant Disease ◽

10.1094/pdis-12-10-0899 ◽

2011 ◽

Vol 95 (8) ◽

pp. 921-926 ◽

Cited By ~ 32

Author(s):

Kimberly S. Chapman ◽

George W. Sundin ◽

Janna L. Beckerman

Keyword(s):

Fungicide Resistance ◽

Mycelial Growth ◽

Venturia Inaequalis ◽

Apple Scab ◽

Field Resistance ◽

Single Spore ◽

Mycelium Growth ◽

Thiophanate Methyl ◽

Development Of Resistance

Venturia inaequalis, the causal agent of apple scab, is controlled primarily by fungicides. Long-term, extensive fungicide use has led to the development of resistance to multiple fungicides. To assess fungicide resistance, isolates of V. inaequalis were collected from Indiana and Michigan orchards. Single-spore derived isolates were evaluated by mycelium growth assays with previously determined discriminatory doses on media containing dodine, kresoxim-methyl, myclobutanil, or thiophanate-methyl. Of 195 isolates tested, 5.2, 0.7, 57.0, and 92.6% of isolates were found to be resistant to dodine, kresoxim-methyl, myclobutanil, and thiophanate-methyl, respectively. This is the first report of kresoxim-methyl field resistance in these states. Isolates resistant or shifted to a single fungicide were often found to have multiple fungicide resistance. Of all isolates tested, 38% were identified as resistant or shifted to two fungicides, and 12% were resistant or shifted to all four fungicides tested. No fitness penalty was found for isolates resistant to multiple fungicides based on a statistical analysis of mycelial growth and conidial production.

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Assessing the potential of plains zebra to maintain African horse sickness in the Western Cape Province, South Africa

10.1101/751453 ◽

2019 ◽

Author(s):

Thibaud Porphyre ◽

John D. Grewar

Keyword(s):

South Africa ◽

Western Cape ◽

African Horse Sickness ◽

Western Cape Province ◽

Tariff Barrier ◽

Source Of Infection ◽

Stochastic Vector ◽

Reservoir Hosts ◽

Plains Zebra

AbstractAfrican horse sickness (AHS) is a disease of equids that results in a non-tariff barrier to the trade of live equids from affected countries. AHS is endemic in South Africa except for a controlled area in the Western Cape Province (WCP) where sporadic outbreaks have occurred in the past 2 decades. There is potential that the presence of zebra populations, thought to be the natural reservoir hosts for AHS, in the WCP could maintain AHS virus circulation in the area and act as a year-round source of infection for horses. However, it remains unclear whether the epidemiology or the ecological conditions present in the WCP would enable persistent circulation of AHS in the local zebra populations.Here we developed a hybrid deterministic-stochastic vector-host compartmental model of AHS transmission in plains zebra (Equus quagga), where host populations are age- and sex-structured and for which population and AHS transmission dynamics are modulated by rainfall and temperature conditions. Using this model, we showed that populations of plains zebra present in the WCP are not sufficiently large for AHS introduction events to become endemic and that coastal populations of zebra need to be >2500 individuals for AHS to persist >2 years, even if zebras are infectious for more than 50 days. AHS cannot become endemic in the coastal population of the WCP unless the zebra population involves at least 50,000 individuals. Finally, inland populations of plains zebra in the WCP may represent a risk for AHS to persist but would require populations of at least 500 zebras or show unrealistic duration of infectiousness for AHS introduction events to become endemic.Our results provide evidence that the risk of AHS persistence from a single introduction event in a given plains zebra population in the WCP is extremely low and it is unlikely to represent a long-term source of infection for local horses.

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