scholarly journals Full-season and post-harvest applications of sterol-inhibiting fungicides to reduce ascospore formation in Venturia inaequalis

2005 ◽  
Vol 71 (1) ◽  
pp. 9-15 ◽  
Author(s):  
A.R. Biggs ◽  
J. Warner
Keyword(s):  
Venturia Inaequalis ◽  
Apple Scab ◽  
Post Harvest ◽  
Highly Effective ◽  
Causal Fungus ◽  
Ascospore Production ◽  
Ascospore Formation ◽  
Better Than

Several sterol-inhibiting (SI) fungicides were tested in post-harvest and full-season spray programs for the inhibition of ascospore formation by Venturia inaequalis, the causal fungus of apple scab. Post-harvest treatments with flusilazole and diniconazole were comparable to or better than those with benomyl and suppressed ascospore production by 55 to 90 %, although bitertanol stimulated ascospore production by up to 52 %. When applied nine times in full-season programs, bitertanol, flusilazole, and triflumizole reduced ascospore formation to a degree similar to or greater than that achieved with dodine. Full-season programs with SI fungicides in combination with mancozeb were highly effective for reducing ascospore production.

scholarly journals Effect of Timing of Application of the Biological Control Agent Microsphaeropsis ochracea on the Production and Ejection Pattern of Ascospores by Venturia inaequalis

2004 ◽  
Vol 94 (12) ◽  
pp. 1305-1314 ◽  
Author(s):  
O. Carisse ◽  
D. Rolland
Keyword(s):  
Biological Control ◽  
Biological Control Agent ◽  
Venturia Inaequalis ◽  
Apple Scab ◽  
Control Agent ◽  
Sterile Leaf ◽  
Ascospore Production ◽  
Fall Application ◽  
Leaf Disks

Field and in vitro trials were conducted to establish the influence of the biological control agent Microsphaeropsis ochracea on the ejection pattern of ascospores by Venturia inaequalis and on apple scab development, and to establish the best timing of application. The ejection pattern of ascospores was similar on leaves sprayed with M. ochracea and on untreated leaves. Fall application of M. ochracea combined with a delayed-fungicide program was evaluated in orchards with intermediate and high scab risk. For both orchards, it was possible to delay the first three and two infection periods in 1998 and 1999, respectively, without causing significant increase or unacceptable leaf and fruit scab incidence. To evaluate the best timing of application, sterile leaf disks were inoculated with V. inaequalis and then with M. ochracea 0, 2, 4, 6, 8, 10, 12, 14, and 16 weeks later. After incubation under optimal conditions for pseudothecia development, the number of ascospores was counted. Similarly, M. ochracea was sprayed on scabbed leaves on seven occasions from August to November 1999 and 2000. Leaves were overwintered on the orchard floor and ascospore production was evaluated the following spring. Ascospore production was reduced by 97 to 100% on leaf disks inoculated with M. ochracea less than 6 weeks after inoculation with V. inaequalis, but ascospore production increased with increasing period of time when M. ochracea was applied 8 to 16 weeks after the inoculation with V. inaequalis. In the orchard, the greatest reduction in production of ascospores (94 to 96% in 2000 and 99% in 2001) occurred on leaves sprayed with M. ochracea in August. The production of ascospores was reduced by 61 to 84% in 2000 and 93% in 2001 on leaves sprayed with M. ochracea in September, reduced by 64 to 86% in 2000 and 74 to 89% in 2001 on leaves sprayed in October, and reduced by 54 and 67% in 2000 and 2001, respectively, on leaves sprayed in November. It was concluded that M. ochracea should be applied in August or September and that ascospore maturation models and delayed-fungicide program could be used in orchards treated with this biological control agent.

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.

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 `QAS-13': A New Promising Cold-hardy Scab-resistant Apple Selection

HortScience ◽  
1995 ◽  
Vol 30 (4) ◽  
pp. 762E-762
Author(s):  
Raymond L. Granger ◽  
Y. Groleau ◽  
C. Fortin ◽  
Gilles L. Rousselle ◽  
L.P.S. Spangelo
Keyword(s):  
Venturia Inaequalis ◽  
Apple Scab ◽  
Average Diameter ◽  
Soil Conditions ◽  
Greenish Yellow ◽  
Red Color ◽  
Botryosphaeria Obtusa ◽  
Cold Hardy ◽  
Better Than ◽  
Made In

`QAS-13' is an advanced apple selection that has a proven performance and is in the process of becoming a new cultivar that carries the Vf gene for resistance to apple scab (Venturia inaequalis Cke. Wint.) derived from `Malus floribunda 821'. It combines field immunity to scab and cold tolerance under Quebec climate and soil conditions. The Ott.521 (Melba x 11-51) x `Spartan' cross was made in Ottawa in 1968. The fruits are very attractive and exhibit a smooth and shiny finish somewhat similar to that of `Spartan'. Their glossy, medium- to dark-red color is slightly striped over a greenish-yellow background and covers up to 85% of the fruit surface. Their picking season coincides with that of `Spartan', which is ≈1 week before that of `Red Delicious'. They are round-oblate to oblate in shape with an average diameter of 70 to 75 mm and weigh ≈140 g/fruit. The skin is smooth, thin, and moderately tough, with widely spaced conspicuous beige lenticels. Both the stem and calyx cavities are fairly deep. The stem resembles that of `McIntosh'. the `QAS-13' apples keep better than `McIntosh' apples both in CA and air storages. Taste panelists have consistently ranked the `QAS-13' apples above `McIntosh' apples both at harvest and after storage. The `QAS-13' trees are less vigorous than those of `McIntosh', but more productive. However, they have exhibited a slight susceptibility to frog eye leaf spot (Botryosphaeria obtusa) similar to that of `McIntosh'.

scholarly journals Seasonal and Cross-Seasonal Timing of Fungicide Trunk Injections in Apple Trees to Optimize Management of Apple Scab

Plant Disease ◽  
2016 ◽  
Vol 100 (8) ◽  
pp. 1606-1616 ◽  
Author(s):  
Srđan G. Aćimović ◽  
Anthony H. VanWoerkom ◽  
Thomas Garavaglia ◽  
Christine Vandervoort ◽  
George W. Sundin ◽  
...  
Keyword(s):  
United States ◽  
Venturia Inaequalis ◽  
Apple Scab ◽  
The United States ◽  
Apple Trees ◽  
Seasonal Timing ◽  
Scab Control ◽  
Better Than ◽  
Spray Applications

To optimize the number and timing of trunk injections for season-long control of apple scab (Venturia inaequalis), we evaluated 1 to 2 and 4 seasonal and cross-seasonal injections of potassium phosphites and synthetic fungicides and quantified residues in leaves and fruit. Phosphites accumulated in the canopy at the highest concentrations, aligned well in time with scab suppression, and gave better leaf scab control of 41.8 to 73.5% than propiconazole (16.9 to 51.5%) or cyprodinil + difenoconazole (5.4 to 17.4%). More injections of phosphites controlled leaf scab better than fewer (23.7% versus 48.2%), and more fungicide injections resulted in 21.9 to 51.1% better leaf scab control than fewer. Leaf scab control with phosphites was only 3.2 to 13.9% better with 4 cross-seasonal compared with 4 seasonal injections, while 1 to 2 seasonal compared with 1 to 2 cross-seasonal injections improved scab control only for 4.2 to 22.1%. On shoots, injected phosphites provided comparable or for 4.4 to 10.5% and 22.3 to 41.4% better scab control than spray standards. On fruit, injected phosphites slightly improved control compared with sprayed phosphites or the sprayed fungicide standard (33.4 to 40.8%). Two seasonal injections of phosphites controlled shoot scab 5.7% better than 9 spray applications. Five sprays of cyprodinil + difenoconazole controlled scab better than their injections. Fruit residues of phosphites reached 2.8 ppm and declined in all treatments except in 2 seasonal injections and phosphite sprays. Cyprodinil and difenoconazole fruit residues reached 0.02 and 0.07 ppm and declined sharply toward the end of the season. These were far below the United States, Codex, and EU MRL-s of 1, 0.8, and 0.5 ppm for difenoconazole, and 1.7, 2, and 1 ppm for cyprodinil, respectively.

scholarly journals Suppression of Venturia inaequalis (apple scab) ascospore production using autumnapplied fungicides

2008 ◽  
Vol 61 ◽  
pp. 54-58
Author(s):  
P.N. Wood ◽  
R.M. Beresford ◽  
T.J. Taylor
Keyword(s):  
Fungicide Resistance ◽  
Venturia Inaequalis ◽  
Apple Scab ◽  
Black Spot ◽  
Field Application ◽  
Copper Hydroxide ◽  
Apple Leaves ◽  
Application Rates ◽  
Resistant Strains ◽  
Ascospore Production

In autumn 2006 apple leaves with visible scab (black spot) symptoms were collected at the time of leaf fall and dipped in fungicides at concentrations equivalent to field application rates The leaves were overwintered on gravel and ascospore production measured on three dates during the following spring using suction spore traps Of ten fungicides tested myclobutanil trifloxystrobin captan dodine tolyfluanid and cyprodinil either reduced or delayed ascospore production by Venturia inaequalis during the following spring compared with a waterdipped control Metiram dithianon urea and copper hydroxide had a minimal effect on ascospore production Leaves from a separate orchard trial produced significantly fewer ascospores after myclobutanil treatment than after captan treatment Captan and tolyfluanid are recommended for autumn application to control scab because they significantly reduced or delayed ascospore production and have a low risk of selecting resistant strains of V inaequalis Although also effective myclobutanil trifloxystrobin dodine and cyprodinil should not be used for autumn application because of the risk of fungicide resistance

Sign in / Sign up

Export Citation Format

Share Document