scholarly journals A New Phytosanitary Method to Reduce the Ascospore Potential of Venturia inaequalis

Plant Disease ◽  
2017 ◽  
Vol 101 (3) ◽  
pp. 414-420 ◽  
Author(s):  
Franziska M. Porsche ◽  
Barbara Pfeiffer ◽  
Andreas Kollar
Keyword(s):  
Leaf Litter ◽  
Yeast Extract ◽  
Untreated Control ◽  
Venturia Inaequalis ◽  
Apple Scab ◽  
Nutrient Media ◽  
Apple Leaves ◽  
Litter Decay ◽  
Ascospore Discharge ◽  
Infection Pressure

Ascospores of Venturia inaequalis, released from pseudothecia in overwintered, infected apple leaves, serve as the primary inoculum for apple scab. In this study, we tested a new sanitation strategy to reduce ascospore inoculum under orchard conditions over three overwintering periods. After leaf fall, nutrient media containing different concentrations of degraded casein or a yeast extract from Saccharomyces cerivisiae were applied to leaf litter infected with apple scab. The application of 30 and 60% yeast extract showed the greatest efficacy, and significantly reduced ascospore discharge by 99% (P < 0.01) in 2013 and 2014. The efficacy of the treatments did not differ from treatment with 5% urea (P > 0.05). Leaf litter decay was accelerated in the plots treated with yeast extract compared with untreated control plots. Moreover, apple leaves treated with yeast extract had completely decayed due to earthworm activity before ascospore maturity. In comparison, up to 26% of the leaves in untreated control plots had not decayed. These results suggest that the treatment of leaf litter with yeast extract can almost completely eliminate apple scab inoculum in the course of the whole primary season. These sanitation practices may be beneficial for both organic and conventional cultivation. The reduced infection pressure may allow growers the usage of fungicides with lower efficacy or to reduce the number of applications needed to manage apple scab in spring.

scholarly journals Comparative Studies on the Effect of Adjuvants with Urea to Reduce the Overwintering Inoculum of Venturia inaequalis

Plant Disease ◽  
2019 ◽  
Vol 103 (3) ◽  
pp. 531-537 ◽  
Author(s):  
Janna Beckerman ◽  
Chelsi Abbott
Keyword(s):  
Leaf Litter ◽  
Litter Decomposition ◽  
Comparative Studies ◽  
Venturia Inaequalis ◽  
Apple Scab ◽  
Organic Surfactant ◽  
Comparable Performance ◽  
Improved Sanitation ◽  
Litter Degradation ◽  
Ascospore Production

A 2-year study on the use of organic and conventional adjuvants alone, or mixed with urea, was conducted for management of overwintering inoculum of the apple scab pathogen, Venturia inaequalis. Select adjuvants (LI 700, Bond Max, Latron B-1956, and Organic Wet Betty [OWB]) have the potential to hasten urea-driven leaf litter decomposition and reduce V. inaequalis overwintering inoculum comparable to urea, and that one organic surfactant could perform the same level of leaf decomposition as urea. Combinations of adjuvants with urea significantly improved leaf litter degradation compared with urea alone, concomitant with reducing the number of pseudothecia present and pseudothecium fertility. We demonstrate that the combination of urea with Bond Max or OWB reduced pseudothecia fertility and ascospore production to less than 5% in the remaining pseudothecia, a significantly greater reduction than with urea alone. These results suggest that conventional growers combine urea with Bond Max or OWB to more effectively reduce overwintering inoculum, and that the adjuvant OWB can provide organic growers with comparable performance to urea used in conventional orchards for improved sanitation.

scholarly journals Efficacy of Sterol-Inhibiting Fungicides on the Control of Scab Disease (Venturia Inaequalis) in Apple Tree

2019 ◽  
Vol 4 (6) ◽  
pp. 101-103
Author(s):  
Edlira Shahinasi ◽  
Ferdi Brahushi
Keyword(s):  
Untreated Control ◽  
Apple Tree ◽  
Venturia Inaequalis ◽  
Apple Scab ◽  
Disease Index ◽  
Golden Delicious

Apple scab, caused by Venturia Inaequalis is one of the most problematic diseases of apples in Korça region. The control of this disease requires different applications of fungicides. The aim of the study was the estimation of efficacy of sterol-inhibiting fungicides such as myclobutanil and penconazole on the control of scab disease. The effectiveness of fungicides was evaluated for two cultivars Golden Delicious and Starking and the minimum and the maximum recommended doses were applied. The obtained results showed that scab prevalence in leave ranges from 79.2% to 85.6% respectively in untreated trees of Golden Delicious and Starking cultivars. The scab prevalence of leaves in apples treated with pesticides ranges from 18.1% in Golden Delicious cultivar to 22.2% in Starking cultivar, meanwhile the scab prevalence in fruit varies from 4.2% in Starking cultivar to 6.1% in Golden Delicious cultivar.  The disease index of leave in untreated control varies from 38.4% to 40.1% respectively for Golden Delicious cultivar and Starking cultivar, while the severity of fruit in untreated trees varies from 45.6% in Starking cultivar to 49.0% in Golden cultivar. Therefore, the data showed that the uses of sterol-inhibiting fungicides were effective in the control of scab disease.

Evaluation of two methods for assessing ascospore productivity of the apple scab pathogen, Venturia inaequalis

1981 ◽  
Vol 59 (6) ◽  
pp. 965-968
Author(s):  
C. C. Heye ◽  
J. H. Andrews ◽  
E. V. Nordheim
Keyword(s):  
Leaf Litter ◽  
Coefficient Of Variation ◽  
Unit Area ◽  
Venturia Inaequalis ◽  
Apple Scab ◽  
Dry Weight ◽  
Weight Basis ◽  
Square Roots ◽  
Leaf Material ◽  
Normally Distributed

The standard water bubbler and a modified tower aspirator for quantifying ascospore productivity were compared. Samples, each consisting of 50 discs, were cut randomly from scab-infected McIntosh apple leaf litter in the spring and 18 samples were processed by each method. The square roots of hemocytometer counts adjusted for unit area or gram dry weight of leaf samples were found to be normally distributed. More spores were harvested from the same amount of leaf material with the bubbler than with the tower. The coefficient of variation for spore yields expressed on a per area or a per gram dry weight basis was smaller for the tower method than for the bubbler, although the values were not significantly different. Where detection of low ascospore productivity is not essential, the tower method is preferable in terms of ease, speed of operation, and the potential for electronic enumeration of harvested ascospores.

scholarly journals Fungal communities isolated from dead apple leaves from orchards in Quebec

2005 ◽  
Vol 77 (3) ◽  
pp. 129-134 ◽  
Author(s):  
J. Bernier ◽  
O. Carisse ◽  
T.C. Paulitz
Keyword(s):  
North America ◽  
Venturia Inaequalis ◽  
Apple Scab ◽  
Causal Agent ◽  
Biocontrol Agents ◽  
Fungal Communities ◽  
Malus Pumila ◽  
Apple Leaves

Venturia inaequalis, the causal agent of apple scab, overwinters in apple (Malus pumila) leaves on the orchard floor by producing pseudothecia. The objectives of this survey were to make a collection of fungi to be subsequently tested for their potential as psychrophile biocontrol agents against V. inaequalis and to acquire knowledge on the diversity of the microflora of dead apple leaves. Fungi were recovered from dead apple leaves collected in the spring and fall of 1993. A total of 345 isolates from 49 genera were identified. Fifteen gene were not previously recorded as colonizers of apple leaves in North America.

scholarly journals Organic apple growing using sanitation treatments against apple scab

2007 ◽  
Vol 13 (1) ◽  
Author(s):  
F. Abonyi ◽  
I. J. Holb
Keyword(s):  
Untreated Control ◽  
Primary Infection ◽  
Venturia Inaequalis ◽  
Apple Scab ◽  
Apple Orchard ◽  
Apple Cultivar ◽  
Lime Sulphur ◽  
Fallen Leaves

Effects or sanitation practices were evaluated on primary and autumn infection by Venturia inaequalis in an organic apple orchard at Eperjeske on the moderately scab-susceptible apple cultivar Jonathan in 2005 and 2006. Evaluated sanitation practices were: i) collection of fallen leaves in autumn; ii) destroying fallen leaves by disc cultivation in autumn; iii) spraying fallen leaves with 2% lime sulphur in autumn; iv) spraying fallen leaves with 2% lime sulphur in autumn and then collection of fallen leaves in autumn; and v) untreated control. In both years, most sanitation practices reduced significantly (P< 0.05) scab incidence in the primary infection periods compared to untreated control. The highest leaf scab incidence was observed in the untreated plots (26:2 and 24.3% in 2005 and 2006, respectively), while the lowest was in the treatments of spraying fallen leaves with 2% lime sulphur combined with collection of fallen leaves (11.7 and 12.3% in 2005 and 2006, respectively).

Benomyl-marked populations of Chaetomium globosum: survival on apple leaves with and without benomyl and antagonism to the apple scab pathogen, Venturia inaequalis

1985 ◽  
Vol 31 (3) ◽  
pp. 251-255 ◽  
Author(s):  
Daniel Cullen ◽  
John H. Andrews
Keyword(s):  
Resistant Strain ◽  
Venturia Inaequalis ◽  
Apple Scab ◽  
Chaetomium Globosum ◽  
Wild Type ◽  
Population Densities ◽  
Apple Trees ◽  
Initial Inoculum ◽  
Apple Leaves ◽  
Rate Of Decline

Resistance to the fungicide benomyl (BenR) was induced with N-methyl-N′-nitro-N-nitrosoguanidine in Chaetomium globosum isolated from apple leaves. The population densities of a resistant strain reintroduced to leaves on apple trees in an orchard were determined at 3 h, and 1 and 3 weeks following inoculation. Relative to wild-type parents, BenR populations declined more rapidly on orchard trees, but the rate of decline was reduced by amending initial inoculum with 18.5 ppm benomyl. Survival of BenRC. globosum increased 40–58% relative to BenRC. globosum applied without benomyl. In growth chamber experiments with potted apple seedlings, the BenR strain was as antagonistic as were the wild-type parents to the scab pathogen, Venturia inaequalis. The marked strain alone did not significantly reduce scab infection on saplings in the field; however, when it was applied with benomyl, scab severity was significantly (P = 0.01) less than with benomyl alone.

EFFECTS OF SEASONAL FUNGICIDE SPRAYS ON PERITHECIUM FORMATION AND ASCOSPORE PRODUCTION IN VENTURIA INAEQUALIS

1975 ◽  
Vol 55 (3) ◽  
pp. 737-742 ◽  
Author(s):  
R. G. ROSS ◽  
R. J. NEWBERY
Keyword(s):  
Venturia Inaequalis ◽  
Apple Scab ◽  
Malus Pumila ◽  
In Vitro Production ◽  
Ascospore Discharge ◽  
Malus Pumila Mill ◽  
Terminal Shoot ◽  
Vitro Production ◽  
Ascospore Production

Seasonal sprays of the systemic fungicides benomyl, thiophanate-methyl, Bay Dam 18654 and Bavistin applied for the control of apple scab, Venturia inaequalis (Cke.) Wint., either completely or almost completely suppressed the production of ascospores in apple (Malus pumila Mill.) leaves overwintered in the orchard. In vitro production of perithecia on leaves sterilized with propylene oxide was also inhibited by these sprays, although some treatments suppressed ascospore discharge in overwintered leaves that failed to inhibit perithecium formation on the sterile leaves. Ascospore production was also reduced in leaves from spur clusters that had been sprayed with Dikar and metiram. In terminal shoot leaves from Dikar-sprayed trees, ascospore production was higher in leaves collected from near the tip than in leaves collected from near the base of the terminal growth.

scholarly journals Role of urea in the reduction of apple primary infections by Venturia inaequalis (Cooke) Aderh

2013 ◽  
Vol 55 (1) ◽  
pp. 225-231
Author(s):  
Beata Meszka ◽  
Anna Bielenin
Keyword(s):  
Chemical Control ◽  
Primary Infection ◽  
Venturia Inaequalis ◽  
Apple Scab ◽  
Leaf Fall ◽  
Urea Treatment ◽  
Apple Leaves ◽  
Leaf Infection ◽  
Ascospore Production

The effect of pre-leaf fall of 5% urea treatment on primary infection of apple by <i>Venturia inaequalis</i>, the cause of scab, was investigated in commercial apple orchards of McIntosh cv. in different regions of Poland, at Miłobądz, Sinołęka and Dąbrowice. Additionally, the development of pseudothecia and maturation of ascospores were evaluated in the spring on apple leaves of two cultivars (McIntosh and Gloster) treated with 5% solution of urea. Microscopic observations of leaves showed that urea treatment significantly reduced the number of pseudothecia (by ca. 90%) and ascospore production. Low number of ascospores after urea treatment has strongly affected primary infection of apple by the fungus in all tested orchards. Reduction of leaf infection on control trees was usually more than 30%. Also efficacy of chemical control of apple scab was significantly higher on plots treated with urea.

scholarly journals Ascospore Release and Infection of Apple Leaves by Conidia and Ascospores of Venturia inaequalis at Low Temperatures

1997 ◽  
Vol 87 (10) ◽  
pp. 1046-1053 ◽  
Author(s):  
Arne Stensvand ◽  
David M. Gadoury ◽  
Terje Amundsen ◽  
Lars Semb ◽  
Robert C. Seem
Keyword(s):  
Low Temperatures ◽  
Venturia Inaequalis ◽  
Field Studies ◽  
Leaf Wetness ◽  
Apple Trees ◽  
Infection Period ◽  
Apple Leaves ◽  
Ascospore Discharge ◽  
Ascospore Release ◽  
The Mean

Mills' infection period table describes the number of hours of continuous leaf wetness required at temperatures from 6 to 25°C for infection of apple leaves by ascospores of Venturia inaequalis and reports that conidia require approximately two-thirds the duration of leaf wetness required by ascospores at any given temperature. Mills' table also provides a general guideline that more than 2 days of wetting is required for leaf infection by ascospores below 6°C. Although the table is widely used, infection times shorter than those in the table have been reported in lab and field studies. In 1989 a published revision of the table eliminated a potential source of error, the delay of ascospore release until dawn when rain begins at night, and shortened the times reported by Mills for ascospore infection by 3 h at all temperatures. Data to support the infection times below 6°C were lacking, however. Our objective was to quantify the effects of low temperatures on ascospore discharge, ascospore infection, and infection by conidia. In two of three experiments at 1°C, the initial release of ascospores occurred after 131 and 153 min. In the third experiment at 1°C, no ascospores were detected during the first 6 h. The mean time required to exceed a cumulative catch of 1% was 143 min at 2°C, 67 min at 4°C, 56 min at 6°C, and 40 min at 8°C. At 4, 6, and 8°C, the mean times required to exceed a cumulative catch of 5% were 103, 84, and 53 min, respectively. Infection of potted apple trees by ascospores at 2, 4, 6, and 8°C required 35, 28, 18, and 13 h, respectively; substantially shorter times than previously were reported. In parallel inoculations of potted apple trees, conidia required approximately the same periods of leaf wetness as ascospores at temperatures from 2 to 8°C, rather than the shorter times reported by Mills or the longer times reported in the revision of the Mills table. We propose the following revisions to infection period tables: (i) shorter minimum infection times for ascospores and conidia at or below 8°C, and (ii) because both ascospores and conidia are often present simultaneously during the season of ascospore production and the required minimum infection times appear to be similar for both spore types, the adoption of a uniform set of criteria for ascosporic and conidial infection based on times required for infection by ascospores to be applied during the period prior to the exhaustion of the ascospore supply. Further revisions of infection times for ascospores may be warranted in view of the delay of ascospore discharge and the reduction of airborne ascospore doses at temperatures at or below 2°C.

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