scholarly journals Effect of Fall Application of Fungal Antagonists on Spring Ascospore Production of the Apple Scab Pathogen, Venturia inaequalis

2000 ◽  
Vol 90 (1) ◽  
pp. 31-37 ◽  
Author(s):  
Odile Carisse ◽  
Vincent Philion ◽  
Daniel Rolland ◽  
Julie Bernier
Keyword(s):  
Large Scale ◽  
Venturia Inaequalis ◽  
Apple Scab ◽  
Leaf Fall ◽  
Natural Conditions ◽  
Fungal Isolates ◽  
Trichoderma Sp ◽  
Ascospore Production ◽  
Fall Application ◽  
Leaf Disks

The influences of Microsphaeropsis sp., M. arundinis, Ophiostoma sp., Diplodia sp., and Trichoderma sp., all antagonists of Venturia inaequalis, on ascospore production were evaluated under natural conditions and compared with urea and Athelia bombacina, a known antagonist. In the autumn, the fungi were applied to leaf disks artificially inoculated with V. inaequalis and to scabbed apple (Malus domestica) leaves incubated under controlled and natural conditions. In addition, large-scale trials were conducted with Microsphaeropsis sp. applied either as a foliar postharvest spray or as a ground application at 90% leaf fall. All fungal isolates, except Ophiostoma sp., were recovered from the leaf material that overwintered in the orchard. All treatments, except those with Ophiostoma sp., resulted in a significant reduction in V. inaequalis ascospore production on the leaf disks incubated under controlled conditions or in the orchard. In 1997, leaves with apple scab lesions treated with urea or Microsphaeropsis sp. produced significantly fewer ascospores of V. inaequalis than did nontreated leaves, with a reduction of 73.0 and 76.3%, respectively. In 1998, leaves treated with Microsphaeropsis sp., urea, Trichoderma sp., A. bombacina, and M. arundinis reduced ascospore production by 84.3, 96.6, 75.2, 96.6, and 52.2%, respectively. Based on all tests combined, the most efficient isolate was Microsphaeropsis sp. Postharvest applications of Microsphaeropsis sp. reduced the total amount of airborne ascospores trapped by 70.7 and 79.8% as compared with the nontreated plots in 1997 and 1998, respectively. Microsphaeropsis sp. provided a significant and consistent reduction in ascospore production in all tests.

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 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 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 Treatment of overwintering apple leaves to reduce primary inoculum of apple black spot

2003 ◽  
Vol 56 ◽  
pp. 95-99
Author(s):  
K. Tshomo ◽  
I.J. Horner ◽  
M. Walter ◽  
A. Stewart ◽  
M.V. Jaspers
Keyword(s):  
Venturia Inaequalis ◽  
Black Spot ◽  
Field Trials ◽  
Water Control ◽  
Primary Inoculum ◽  
Apple Leaves ◽  
Fungal Isolates ◽  
Glass Slides ◽  
Ascospore Production ◽  
Nutrient Amendments

Field trials were conducted in Hawkes Bay and Lincoln into methods of treating overwintering apple leaves to reduce ascospore production by the apple black spot pathogen Venturia inaequalis The leaf treatments comprised three levels of nutrient amendments (including a water control) and five levels of saprophytic fungal isolates (including a nofungus control) in a factorial design Leaves were left to overwinter on the orchard floor and in spring the V inaequalis ascospores released were trapped on glass slides and counted Ascospore numbers were reduced (Plt;005) by the leaf amendment urea which alone caused 73 reduction but not by the BioStarttrade; product The effect of fungal isolates was not significant (P012) although when combined with the water treatment the isolates Chaetomium Phoma and Epicoccum spp and Trametes versicolor reduced numbers of ascospores by 33 27 15 and 28 respectively compared to the nofungus control When combined with urea the Chaetomium isolate reduced ascospore numbers by 92 and 82 compared to the nil fungus/water control treatments in Hawkes Bay and Lincoln respectively indicating that this treatment has potential for reducing primary inoculum of apple black spot

scholarly journals Autumnapplied urea and other compounds to suppress Venturia inaequalis ascospore production

2000 ◽  
Vol 53 ◽  
pp. 387-392
Author(s):  
R.M Beresford ◽  
I.J. Horner ◽  
P.N. Wood
Keyword(s):  
Venturia Inaequalis ◽  
Black Spot ◽  
Leaf Fall ◽  
Single Application ◽  
Apple Trees ◽  
Spot Disease ◽  
Apple Leaves ◽  
Cupric Hydroxide ◽  
Fallen Leaves ◽  
Ascospore Production

The effect of urea applied to apple leaves in autumn on production of ascospores of Venturia inaequalis (black spot) was quantified in four studies Autumn urea at concentrations from 020 reduced ascospore production in spring in proportion to the log of the urea concentration A single application of 5 urea sprayed onto fallen leaves gave an 88 decrease in ascospore production Urea applied to apple trees before leaf fall significantly reduced black spot disease on leaves the following spring in cv Fuji but not in cv Royal Gala Ascospore production was reduced by the fungicide cupric hydroxide but was not affected by a low concentration of fish fertilizer Three methods of ascospore assessment were used to detect differences in ascospore production

scholarly journals Managing Resistance of Venturia inaequalis to the Strobilurin Fungicides

2004 ◽  
Vol 5 (1) ◽  
pp. 3 ◽  
Author(s):  
William W. Turechek ◽  
Wolfram Köller
Keyword(s):  
Fungicide Resistance ◽  
Large Scale ◽  
Venturia Inaequalis ◽  
Apple Scab ◽  
Resistance Management ◽  
Management Program ◽  
Crop Losses ◽  
The Past ◽  
Strobilurin Fungicides ◽  
Low Rate

Over the past thirty years, fungicide resistance has been cited as the cause of large-scale crop losses due to apple scab in a number of commercial orchards in the Northeast. The strobilurins represent the most recent class of fungicides for which the threat of resistance exists. In this article we examine the use of strobilurin fungicides at their highest and lowest labeled rates and as a mixture of the lowest labeled rate with a protectant fungicide in commercial spray programs for efficacy against apple scab as well as their utility in a resistance management program. Our results suggest that anti-resistance properties of high strobilurin rates are superior to low rates and low rate mixtures with a protectant fungicide. Accepted for publication 26 August 2004. Published 8 September 2004.

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 Application of fungicides during leaf fall to control apple scab (Venturia inaequalis) in the following season

2008 ◽  
Vol 61 ◽  
pp. 59-64 ◽  
Author(s):  
R.M. Beresford ◽  
P.N. Wood ◽  
P.W. Shaw ◽  
T.J. Taylor
Keyword(s):  
Fungicide Resistance ◽  
Venturia Inaequalis ◽  
Apple Scab ◽  
Fruit Production ◽  
Leaf Fall ◽  
Apple Orchards ◽  
Resistance Risk ◽  
Chemical Residues ◽  
Integrated Fruit Production

Leaf fall applications of fungicides to reduce scab in apple orchards were investigated to reduce reliance on summer fungicides that can cause trace chemical residues on harvested fruit Two applications of fungicides including captan tolyfluanid myclobutanil and urea were made at 1020 and 5060 leaf fall in four orchard trials in Nelson and Hawkes Bay using the cultivars Royal Gala Braeburn Fuji and Sciros/Pacific Rosetrade; Trial orchards received standard spring and summer fungicide programmes that complied with Integrated Fruit Production and were monitored for leaf and fruit scab in December and at harvest Significant reductions in leaf or fruit scab occurred in three out of five comparisons involving different sites years and cultivars suggesting that autumn applications can reduce scab in the following season Captan and tolyfluanid appeared most useful for autumn application Myclobutanil should not be used because of the fungicide resistance risk Results with urea were variable

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