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IOBC-WPRS Bulletin Vol. 84, 2012

 

IOBC-WPRS Bulletin Vol. 84, 2012

Working Group "Integrated Plant Protection in Fruit Crops", Subgroup "Pome Fruit Diseases".
Proceedings of the 9th International IOBC-WPRS Workshop on Pome Fruit Diseases at Hasselt, Belgium, 29 August - 2 September 2011.
Edited by P. Creemers.
ISBN 978-92-9067-262-3 [XIII + 336 pp.]

 

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DNA arrays for multiplex detection of plant pathogens
B. Lievens

Abstract only

3

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Towards the development of a rapid detection method for bull’s eye rot in apples
A. den Breeyen & C. Lennox

Abstract: Neofabraea alba, one of four Neofabraea species causing bull’s eye rot (BER), occurs
sporadically in South Africa on late maturing apple varieties. Infection in the orchard can occur at
any time during the growing season and incipient infections remain latent until symptom
development after three to five months in storage. Developing a rapid detection method for bull’s
eye rot would allow for early marketing of grower-lots with high disease incidence (DI). The
study assessed both a conventional detection method and the use of paraquat to detect latency.
For the conventional method, fruit was stored at 21°C under high relative humidity for 30 days
and evaluated for DI. For the paraquat method, asymptomatic fruit were surface sterilised and
immersed in a 1% paraquat solution. Fruit were incubated at 21°C in dew chambers and
monitored for symptoms at 7 and 14 days post treatment (dpt). Control fruit were stored for 4
months at -0.5°C. Disease incidence was recorded at 67% for the control treatment, 63% for the
paraquat treatment (14 dpt), 42% for the conventional treatment and 20% for the paraquat
treatment (7 dpt). Only the paraquat treatment (14 dpt) was comparable to the control treatment.
Asymptomatic ‘Cripps Pink’ fruit were harvested monthly from November 2010 to April 2011
and using genus-specific primers, we determined whether N. alba could be detected on orchard
fruit throughout the growing season. Inoculum was detected on orchard fruit as early as four
months before harvest. Rapid detection techniques, including molecular technologies for BER,
will allow for timely and effective disease management strategies.

5-8

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Monilinia fructicola in Switzerland
M. Hilber-Bodmer, M. Jänsch, G. A. L. Broggini, J. Weger, J. E. Frey & A. Patocchi

Abstract only

9

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Characterization of Stemphylium vesicarium populations from Spanish pear orchards
L. Ruz, C. Moragrega, M. Puig, E. Montesinos & I. Llorente

Abstract: Stemphylium vesicarium, is the causal agent of brown spot of pear, a fungal disease
that produces important economical losses in pear growing areas of European countries. Besides
the pathogenicity on pear the fungus is able to grow saprophytically on dead plant material in the
orchard. The quantification of inoculum in the orchard is required for the application of
integrated disease control measures. The assessment of the inoculum is performed through aerial
spore traps. However, not all the spores trapped are pathogenic. Therefore, the characterization of
the populations of the fungus on the basis of their saprophytic-pathogenic profile is required to
define more efficient disease management strategies. Accordingly, the pathogenicity on pear of
125 isolates of S. vesicarium obtained from different sources (air, lesions, leaf plant debris, and
non host plants) in Northeastern Spanish pear orchards was determined. Representative isolates
were characterized at molecular level with RAPD and AFLPs techniques. Several RAPD and
AFLPs fragments were selected to design a duplex PCR specific for S. vesicarium and for pear
pathogenic isolates.

11-15

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Genetic analysis of Stemphylium isolates associated with Brown spot on pear in Belgium
S. van Laer, J. Pannecoucque, W. Van Hemelrijck, P. Creemers & M. Höfte

Abstract only

16

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Epidemiology and control of pear diseases of economic importance
E. Montesinos, P. Vilardell & I. Llorente

Abstract only

19

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Control of inoculum sources of brown spot on pear
P. F. de Jong & J. Köhl

Abstract only

20

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Epidemiological research on the etiology of twig scab as basis for a rational
and ecological disease management

W. van Hemelrijck, E. Croes, J. Keulemans & P. Creemers

Abstract: Scab is one of the key parasites in pome fruit. In favourable weather conditions, a
complete harvest can be destroyed if no control measurements are undertaken. The disease is
caused by the ascomycete Venturia inaequalis and V. pirina on apple and pear, respectively.
Although they are two distinct species, their biological cycle is mainly the same. Two distinctions
can be made, i.e. the appearance of twig scab and the more important contribution of secondary
scab infections on pears. Especially in organic fruit growing, twig scab is a big problem. Until
now, most research concerning scab disease is performed on apples and as such, the disease
management of pear scab is based on that of apple. Based on the two discrepancies in their
biological cycle, we believe that the timing of the fungicides to control pear scab can be better
positioned and that less fungicide sprayings may be needed to control pear scab. For that reason
an IWT (Agency for Innovation by Science and Technology)-funded research project was started
to study pear scab in more detail. In this project the etiology and the importance of twig scab in
the epidemiological cycle of pear scab and its contribution to scab infections is investigated.
Furthermore, the diversity of V. pirina biotypes and their pathogenicity on different plant parts or
cultivars will be determined. The first results indicate that twig scab may be an important factor
in the biological cycle of pear scab and that plant part or type of cultivar do not set up a barrier
for cross infections with scab conidia.

21-27

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Susceptibility of pear (Pyrus communis) cultivars for different strains of Venturia pirina
J. Keulemans, E. Buyse, D. Martens, A. de Landtsheer, B. Daniëls, W. van Hemelrijck & P. Creemers

Abstract: Pear scab, caused by the fungus Venturia pirina, is one of the most important diseases
in European pear, especially in organic culture systems. In order to develop adapted control
strategies there is a need for a better knowledge of pear susceptibility/resistance to scab and the
plant pathogen interaction. Therefore, we performed inoculations of pear cultivars with different
V. pirina strains. Germination of conidia and appressorium formation in a compatible
combination were observed on in vitro plants 8 and 12 hours after inoculation, respectively. The
growth of the fungus on the leaf continued even until 14 days after inoculation with ramifications
of the germination tube and several appressoria from one spore. The same observations were
made after inoculation of pear leaves with Venturia inaequalis. For the cultivars Conference,
Doyenné du Comice and Durondeau clear differences in susceptibility were found after
inoculation of grafted plants in the greenhouse according to the origin of the scab strain. Only
strains isolated from the cultivar itself could give sporulation on leaves. Strain specificity among
cultivars was less pronounced for chlorosis than for sporulation. Specific symptoms were found
on Durondeau (sporulation on twigs) and on Doyenné (pin points after inoculation with
Conference isolates).

29-37

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Distribution and development of European pear rust in Latvia and relationship
between severity and yield

R. Rancane, B. Lace & G. Lacis

Abstract: Pear (Pyrus communis L.) is the second most common pome fruit crop in Latvia. A
critical situation with the severity of disease – European pear rust (caused by Gymnosporangium
sabinae) – has been observed in gardens of Latvia, where plant protection products are not used
at all or in very limited amounts. Therefore the disease becomes more and more common. The
agent of pear rust is an obligatory parasite with incomplete development cycle, which requires
both pear and juniper. In case of strong infection disease features could be found not only on pear
leaves, but also on branches and fruits. The disease can cause significant crop losses, as well as
gradual destruction of trees. Therefore the aim of study was to determine the incidence level of
European pear rust infection in Latvia and to analyze peculiarities of disease development. For
the detection of European pear rust incidence 33 pear orchards in different regions of Latvia were
evaluated, whereas disease development was investigated for three years at the pear collection of
the Latvia State Institute of Fruit-Growing. Severity of pear rust was scored using scale of points
(0-5) indicating average number of infected leaves per tree. European pear rust severity results
showed significant difference over the years of evaluation. The incidence and spread of the
disease was increasing during more humid growth periods. There were no resistant cultivars
among the tested ones, only variability of susceptibility. Results showed that high severity of pear
rust infection has significant influence on pear yield.

39-45

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Host-plant resistance and biodiversity
C. Gessler & G. A. L. Broggini

Extended abstract

49-50

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CG-Gala: a Gala ameliorated by adding scab resistance gene HcrVf2
from Malus floribunda 821 and the candidate fire blight resistance genes
from Malus cv Evereste

C. Gessler & G. A. L. Broggini

Abstract only

51

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Practical observations on the presence of AP disease (‘Candidatus Phytoplasma mali’) in Trentino (Italy)
L. Mattedi, A. M. Ciccotti, F. Forno, F. Pedrazzoli, P. Bragagna, M. Filippi, M. Deromedi, P. L. Bianchedi

Abstract: An epidemic spread of apple proliferation, a disease caused by ‘Candidatus
Phytoplasma mali’, started in Trentino (north-eastern Italy) in 1998. This disease was already
known in this region, as its first report dates back to 1951, but this was the first time that it
showed an epidemic behaviour, spreading over both mountain and bottom-valley environments.
Since 2008 the distribution of this disease appears to be locally, again due to a typical “recovery”
phenomenon. In this note some field observations carried out in two research projects, funded by
Provincia di Trento (SMAP1 and SMAP2), are reported. Symptoms, transmission trials by insect
vectors and root bridges, monitoring surveys, practical control experiences and examples for
“recovery” are presented.

55-60

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Presence of Candidatus Phytoplasma mali in apple trees and apple suckers
G. Peusens, C. Duchêne, P. Lepoivre & T. Beliën

Abstract: In top fruit production an infection with Candidatus Phytoplasma mali can cause
severe damage and economic losses to the crop. Occurrence of both diseases, apple proliferation
in apple and pear decline in pear, has been reported in several European countries. In Belgium
only symptomatic trees of apple proliferation (AP) were observed sporadically and eradicated in
the past. In a recent research project a survey was carried out to obtain information on the
presence of AP in asymptomatic apple trees. Root samples of apparently healthy trees were
collected in different apple orchards (production and private) and analysed by real-time PCR.
Results confirmed the presence of the pathogen in both symptomatic and asymptomatic trees. As
some Cacopsylla spp. are able to transmit Ca. P. mali from infected trees to healthy trees within
and between orchards, the dynamic of the psyllid population was studied in 4 apple orchards and
in 5 hawthorn hedges from March till August. Several species were indentified: C. mali,
C. melanoneura and C. picta in apple, C. melanoneura, C. peregrina, C. affinis and C. crataegi
in hawthorn. PCR- analysis of individuals of C. mali and C. peregrina revealed their infectivity
but in transmission trials performed with C. mali under lab conditions no transfer of AP to an
artificial feeding source could be obtained.

61-69

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Development of strategies for fire blight control in organic fruit growing
S. Kunz, A. Schmitt & P. Haug

Abstract: Fire blight (Erwinia amylovora) is the most serious bacterial disease in pome fruit.
Effective control strategies are needed to prevent blossom infections by E. amylovora. In
Germany, many potential control agents have been considered and 64 different preparations were
tested in laboratory trials to select the products with highest efficacy. In thirteen field trials
conducted since 2004 Blossom ProtectTM and Myco-Sin® had the highest efficiencies.
Blossom Protect contains blastospores of the yeast Aureobasidium pullulans. The
blastospores are sensitive to fungicides that are used for apple scab control and, in some cases A.
pullulans enhanced fruit russet when applied during bloom. The increase in fruit russetting
depends on the number of applications and on the variety treated. Therefore spray strategies are
needed controlling both, fire blight and apple scab, without increasing fruit russetting. Fire blight
and apple scab control could be achieved using tank mixtures of Blossom Protect + wettable
sulphur. With a strategy to alternate Blossom Protect applications with sprays of a mixture of
wettable sulphur + Myco-Sin fire blight and apple scab was controlled significantly. In addition,
this strategy reduced the number of Blossom Protect applications to two, and by this, reduced the
risk for fruit russetting.

71-78

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Reduction in ooze formation on fruit trees after repeated fosetyl-Al treatments
in the control of fire blight

T. Deckers, H. Schoofs, W. Verjans, R. Valcke & K. Vrancken

Abstract: Recently, different molecules have been developed for fire blight control with the aim
to induce plant defense reactions on the fruit trees before a fire blight infection occurs. In
Belgium Vacciplant, a compound on the base of laminarin has been registered for this purpose
while in other European countries fosetyl-Al has been registered since many years. These
molecules have no bactericide properties as such, but can change the host susceptibility for fire
blight infections. These plant defense enhancing (PDE) molecules should be applied preventively
before fire blight infections occur: for blossom protection this means that the treatments should
be placed between the green bud and begin bloom stages. In an earlier publication it was shown
that the susceptibility of immature fruits to fire blight infections can be influenced by repeated
treatments of fosetyl-Al applied on the trees as a plant defense inducing molecule. In recent trials
on apple and pear, we have seen a substantial reduction in infected area and in bacterial ooze
formation on the immature fruits when the trees were preventively treated with fosetyl-Al
(Deckers et al., 2011). This reduction in ooze production of the fruits is considered to be a very
interesting factor in the fire blight epidemiology, because it can help to reduce the increase in
bacterial inoculum in the orchard like it usually occurs after trauma blight under natural infection
condition. Recent trials have been done on apple and pear to see if this reduction in ooze
formation after repeated plant defense inducing treatments was also possible on other organs, like
shoots and blossoms. The results of these trials will be discussed in this paper. Finally, the
induction of an abiotic stress in fruit trees by repeated treatments of heavy metals like Cu and Mn
can result in an induction of a plant defense reaction and could be helpful in a fire blight control
strategy under orchard conditions.

79-86

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Present understanding of the epidemiology of the sooty blotch/ flyspeck disease complex
D. R. Cooley

Abstract only

89

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The effect of post-harvest foliar urea applications on tree health
and ascospore production of Venturia inaequalis

R. Norton, C. A. Smith, W. MacHardy & W. Lord

Abstract: Apple scab, caused by Venturia inaequalis, is typically managed by applying frequent
applications of fungicides to prevent infection by ascospores, the only significant source of
primary inoculum. This study investigated the use of single and split post-harvest applications of
5% urea on ascospore production and the effects on tree health. In 2007, 2008, and 2009,
naturally infected ‘Cortland’ leaves were sprayed by hand with urea to (1) determine the most
effective time of application to reduce the production of ascospores and (2) determine if two
2.5% and three 1.6% split applications of urea were more effective than a single 5% urea
application. Treated and untreated leaves were overwintered on the orchard floor and in the
spring ascospores were collected onto slides using a volumetric spore trap in order to calculate
ascospore production. All urea treatments significantly reduced ascospore production compared
to an untreated control. Split applications of two 2.5% urea were more effective at reducing
ascospore production than a single 5% application made immediately post-harvest. The same
urea treatments were applied with an air blast sprayer to ‘Marshal Mac’ trees in 2007, 2008, and
2009 to determine their effects on winter injury, fruit set, foliar nitrogen content, and extension
shoot length. The urea treatments had no adverse effects on winter injury, fruit set, and foliar
nitrogen content.

91-97

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Relationships between Venturia inaequalis potential ascospore dose, aerial ascospore concentration,
climatic risks and scab development; effects on experimental designs

L. Brun, C. Gros, F. Combe & L. Parisi

Abstract: During 2008-2009, in an experimental apple orchard located at Gotheron (Drôme,
France), Venturia inaequalis potential ascospore doses, aerial ascospore concentrations and total
ascospores trapped were compared in different plots of a pure stand and a cultivar mixture with
or without sanitation practices. The climatic risks were evaluated and scab development was
observed on leaves and fruits. A very weak correlation between potential ascospore dose, aerial
ascospore concentration and total ascospore trapped was observed in 2008 in spite of the
experimental design with an edge and a distance of 15 meters separating the plots. In 2009 this
correlation was significantly increased, after putting up a net between the plots. Methodological
effects for the experimental assessment of efficacy of the sanitation practices are discussed.
Moreover, our study permitted in 2009 a field validation of one of the conditions defined by
Stensvand et al. (1997) for infection by ascospores at low temperatures.

99-104

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Dieback of apple trees: a complex syndrome and an increasing problem in Northern Italy (Trentino region)
D. Prodorutti, C. Cainelli, V. Gualandri, D. Profaizer, G. Dallago, A. Branz, L. Delaiti, I. Pertot & G. Angeli

Abstract: Dieback and blight symptoms on apple trees have been increasingly observed in
Trentino (Northern Italy). Stunted growth, chlorotic leaves, cracking, necrosis of the bark and
cankers appear mainly at the base of the trunk and on the graft union. Affected plants commonly
die during the growing season. To identify agronomic and weather conditions promoting the
syndrome, an extensive monitoring was carried out in the main fruit-growing areas of Trentino.
Symptomatic apple trees were sampled and microorganisms colonising the affected tissues were
isolated in order to identify potential causal agents. The highest incidence of the syndrome has
been observed on young stressed plants grown in low fertile soils and cold areas with southsoutheast
exposure. Bacteria (Pseudomonas syringae) and fungi (Phomopsis spp., Nectria spp.,
Botryosphaeriaceae) were isolated from necrosis and cankers. Pathogenicity tests were conducted
to confirm their role in the syndrome.

105-106

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Control of replant disease in apple orchards on sandy soils in the Netherlands
M. Wenneker, P. van der Steeg, G. Korthals & J. Visser

Abstract only

107

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Grain crops and white mustard cultivation or PGPR inoculation alleviate effect of apple replant disease
P. Sobiczewski

Abstract only

108

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Problematic root, stem and shoot diseases on apple in Norway
A. Stensvand, V. Talgø, D.-R. Blystad & A. Sletten

Abstract: The following diseases of roots, stem or shoots of apple are more or less troublesome,
but they all seem to be easily spread by planting material. Twig blight and canker caused by
Diplodia sp. and Phomopsis sp. are new to Norway, but are thus far not widely distributed. Apple
proliferation is widely distributed in the fruit growing areas, while fire blight has not been
observed in the fruit areas, although it is widely spread along the western coast of the country.
European canker, silver leaf and crown- and collar rot are endemic in the country.

109-111

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Emergence of new diseases in pip fruit in Belgium
T. Smets, W. van Hemelrijck, T. Vanwalleghem and P. Creemers

Abstract: The past decades global warming and climate changes resulted in higher temperatures
in spring and summer, more extreme weather conditions and rise in carbon dioxide and ozone
levels. The temperature rise in the central and northern part of Europe has brought about a shift of
some diseases from the southern part of Europe upwards to the more northern regions. Moreover,
these climate changes can bring about changes in plants that will affect their interactions with
pathogens. Changes in plant architecture, for example, may influence the microclimate and as
such the risk of infection. Furthermore, abiotic stress such as heat or drought may also contribute
to plant susceptibility. The past years some upcoming diseases, which may be linked to global
warming or climate changes are noticed in Belgium. For pear, some emerging diseases in
Belgium are Stemphylium vesicarium in the orchard and Phacidiopycnis (stem end rot),
Neofabraea or bull’s eye rot, Phialophora side rot and Coprinus snow mold during storage.
Symptoms of these last three decay fungi are quite similar in an early stage and needs further
detection methods for exact determination. During spring 2011, powdery mildew was for the first
time observed on Conference and Durondeau pears in Belgium, which resulted in strong
russeting symptoms. On apple, black rot (Sphaeropsis malorum) is an upcoming problem which
started in organic Elstar orchards. Besides that secondary diseases can become more dominant as
a consequence of the changed availability in fungicides.

113-122

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Biocontrol and other alternative control methods against pre- and post-harvest pome fruit diseases
M. H. Jijakli

Abstract opnly

125

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Strategies for using plant protection products against apple scab
(Venturia inaequalis) to avoid resistance development

M. de Vlas, P. F. de Jong & B. Heijne

Abstract: Using plant protection products (PPPs) with curative action to control apple scab can
lead to resistance development. We therefore tested strategies for effective scab control that
avoided the use of curative PPPs. In 2010 and 2011, the efficacy of dithianon (Delan), sulphur
(Thiovit) and potassium bicarbonate (Armicarb) on leaves and fruits using different strategies
was tested on the apple cultivar Jonagold at the Randwijk research station. In 2011, the curative
action of difenoconazol (Score) was also tested. In the untreated controls, 52.5% (2010) and
56.7% (2011) of the leaves were infected, and 52.5% (2010) and 90.9% (2011) of the fruits. In
both years, stop-spray treatments (application of treatments immediately at the start of an
infection) with sulphur and dithianon resulted in equal infection incidence and severity on leaves
and fruits compared to the preventive application of dithianon. The effect of the curative
application of potassium bicarbonate was comparable to the other treatments in 2010, but the
number of lesions per leaf was higher than with the preventive treatment using dithianon in that
year. The number of applications was lower with the stop-spray strategy than with the preventive
strategy. However, the stop-spray treatments sometimes took place outside normal working
hours, even at night. We concluded from the trials that effective protection against apple scab is
possible without using curative PPPs, which carry a risk of resistance development. Dithianon
and sulphur can be used effectively as part of a stop-spray strategy.

127-131

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Efficacy of potassium bicarbonate towards scab on pome fruits
W. van Hemelrijck, E. Croes & P. Creemers

Abstract: Scab (Venturia inaequalis on apple and V. pirina on pear) is the key parasite on pip
fruits. Seventy five % of the pesticide use in apple production is related with control of fungal
diseases, in which apple scab has a share of 70%. This high pesticide use is subjected to a great
pressure due to the competition between retailers and supermarkets to reduce the maximum
residue level on the fruits. Furthermore, consumers are more sceptical about the presence of
pesticide residues on fruits. Reduction in pesticide use is possible, for example, by taking
alternative control measures against scab. Pear scab, and to a lesser extent apple scab, does not
only infect fruits and leaves, but gives rise to twig lesions as well. The presence of twig scab
represents a major problem, especially in organic pear growing, as fruit growers lack satisfying
measurements to put an end to the disease. Furthermore, as the use of copper is under discussion,
new alternative control strategies are a must in the organic farming. To this end, the efficacy of
potassium bicarbonate (pbc) to control apple scab was investigated. The mode of action of pbc on
conidial infection and the timing of applications in function of the infection period was
determined. Out of the first trials it was concluded that pbc has a fungistatic activity and has the
best activity towards apple scab when it is applied curatively.

133-138

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Effect of potassium bicarbonate against Venturia inaequalis ascospores in vitro
V. Philion & G. Sambiase

Abstract only

139

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Venturia ascospore reduction by Vinasse not yet a practical solution
B. Heijne, P. F. de Jong & J. Köhl

Abstract only

140

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Biocontrol proteomics: Implication of the pentoses phosphates pathway
in the antagonist effect of Pichia anomala against Botrytis cinerea on apple

A. Kwasiborski, J. Renaut, P. Delaplace, P. Lepoivre & M. H. Jijakli

Abstract only

141

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Application of Boni Protect® against postharvest diseases in integrated apple production
S. Weißhaupt, M. Hinze, A. Weiß, C. Ertl & S. Kunz

Abstract: Postharvest diseases caused by fungi provoke major losses in pome fruit production
every year. To replace (partly or completely) the chemical treatments that are used to fight
postharvest diseases or to support their effect by an additional application the efficiency of Boni
Protect was tested in field trials since 2002. Replacing fungicide treatments before harvest in
trials from 2002 to 2010, Boni Protect showed comparable efficiencies of maximum 89%.
Adding up to two Boni Protect applications to standard fungicide treatments an additional
reduction of infected fruits of maximum 4% could be obtained.

143-149

5.00 €

 

Control of brown spot of pear (Stemphylium vesicarium)
with synthetic antimicrobial peptides and selected Bacillus strains

M. Puig, L. Ruz, C. Moragrega, E. Montesinos & I. Llorente

Abstract: Brown spot of pear is a fungal disease caused by Stemphylium vesicarium that
produces important economical losses in several European pear growing areas. The management
of the disease is based on protective fungicide applications, but the efficacy of disease control is
limited, especially when the disease pressure is high. In order to decrease the disease pressure
new strategies and methods have been introduced. These strategies consist of control of the
inoculum production using sanitation methods, which are based on combinations of leaf litter
removal in winter and biological control agents (Trichoderma spp.) applied during late winter,
spring and summer. In the present work, new methods aimed to optimize the disease control are
evaluated, including the use of new biological control agents to decrease the soil inoculum, and
synthetic antifungal peptides to control infections. Three Bacillus subtilis strains were effective in
inoculum reduction and two synthetic peptides showed a high efficacy in pathogen inhibition and
infection control. These biocontrol strains and synthetic peptides will be further investigated for
their use in integrated management of brown spot of pear.

151-156

5.00 €

 

Carbonates for apple scab control
M. Hinze & S. Kunz

Abstract: Apple scab is caused by Venturia inaequalis. As the fungus developed resistance
against demethylation inhibitors and anilinopyrimidines, these curative fungicides cannot be used
anymore in pome fruit production in many regions. As a result, fruit growers can only use
protective agents for apple scab control. We tested different substances in the greenhouse for
their curative efficacy and some promising substances could be identified. Carbonates in different
formulations reduced the apple scab incidence after curative application clearly, but had no
protective effects. Mixtures of protective fungicides with Omni Protect (a.i. potassium carbonate)
sprayed protectively or curatively could achieve a symptom reduction up to 97%. Omni Protect
controlled apple scab populations resistant to demethylation inhibitors and anilinopyrimidines.

157-161

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Evolution of chemical control on fungal diseases in pome fruits
P. Creemers, W. van Hemelrijck & K. Hauke

Abstract: Economical and pomological factors have increased the sensitivity of modern orchards
for fungal diseases. Different strategies must be integrated in the control measures to achieve a
sustainable production system. The disposal of modern fungicides with a high performance is
only one pillar in disease management. 75% of the pesticide use in apple production is related
with the control of fungal diseases, in which apple scab has a share of 70%. The available
fungicide families (classical protectants, demethylation inhibitors, anilino-pyrimidines,
strobilurins) and the recent developed succinate dehydrogenase inhibitors must be positioned
during the growing season in relation with optimal biological and climatological circumstances.
The combined use of fungicide families with complementary effects on different fungal
developing stages together with a limited number of treatments with one family per season must
prolong the lifetime of modern fungicide families. The flexibility in product choice, doses and
quality care of the application over the different treatments must lead to a durable management of
apple diseases in the orchard. However, with the new regulation replacing Directive 91/414 and
the Framework Directive on the sustainable use of pesticides, products will disappear from the
European market which will give a new challenge in IPM strategies to control pest and diseases.
Besides this agricultural approach, there is the pressure of environmental and consumer groups
on supermarkets to reduce residues on fruits. The competition between retailers is an issue based
on residue levels which are much stronger then the legally MRL (Maximum Residue Limit)
eventually combined with a maximum of active ingredients present on the fruit. The challenge
will be how to manage pest and diseases in the post blossom period until harvest. Sanitation,
optimal timing of spray treatments, adequate application techniques and resistance risk modifiers
will under these prescriptions be the main tools to reach an integrated durable fruit production
structure.

165-176

5.00 €

 

Effects of spray application on the control of fungal diseases in top fruit
P. Triloff, G. Bäcker & S. Kleisinger

Abstract: The progress that has been made in the past two decades has significantly improved
apple scab control, especially during the primary season. This may easily be observed on organic
fruit farms which today reach a level of control at least as good as IP-farms do. Despite this
progress at the end of the growing season at least in more humid climates (e.g. Lake Constance
area) in both growing systems the percentage of highly infected orchards of susceptible varieties
like “Jonagold” statistically is increasing since many years. Since this increase is occurring
despite intensive spray programmes with classical protectant fungicides it may be interesting to
assess for a possible effect of spray application which besides secondary inoculum, shoot growth
and physical infection conditions is a key parameter influencing the epidemics of apple scab in
the secondary season. Based on a canopy related dosing model, the effects of canopy adapted
water volume, forward speed and fan power on spray deposits have been compared with common
dosing and application rules using fixed water volume, preset forward speeds and nominal fan
power. Spray cover from three canopy systems has been analysed on deposits, coverage and
droplet deposit density. The canopy related application could almost compensate a reduction of
water volume per ha as canopy width decreased, leading to very similar coverage and droplet
deposit density on the upper leaf surface and improved spray cover in the centre of broad
canopies. On the lower leaf surface both methods resulted in a strong oversupply increasing as
canopy width increased. Despite improved application efficiency also a canopy related spray
application could not reduce the number of leaves with average deposit densities below
approximately 16cm-2 supposed to be the minimum droplet deposit density for captan. The UVphotographs
also disclosed a small part of the leaves with irregular spots that were not or just
poorly covered because leaves or parts of them where shielded by other leaves, shoots and fruit,
but apparently also have been improperly exposed to the spray mist. If this is assumed to be the
same on young and susceptible leaves, a percentage of the leaf area remains insufficiently
protected, allowing a small fraction of the landed spores to germinate and infect. The risk that
one or more spores land in such a gap and infect, is increasing as the number of spores available
per unit area is increasing. This effect is supposed not to be a question of dosing and water
volume rate but is more related to the random orientation of the individual leaf and its
neighbouring tree structures. Therefore the most effective solution is an early termination of
shoot growth to prevent the development of susceptible tissue as early as possible.

177-190

5.00 €

 

Prospects of the EU project PURE on innovative IPM in pome fruit
B. Heijne

Abstract only

191

0.00 €

 

Fungicide sensitivity of South African apple scab populations
J. C. Meitz, S. G. von Diest, T. Koopman, M. Kidd, J. Roquefort, W. Schwabe & C. L. Lennox

Abstract: The most effective control of apple scab (Venturia inaequalis) is still achieved through
the use of fungicides. However, monitoring of efficacy of active ingredients is required to avoid
unnecessary cost, environmental pollution and health exposure. In this study, the current status of
efficacy of two commonly used classes of fungicides, namely one anilinopyrimidine and an
ergosterol biosynthesis inhibitor, were evaluated. Sampling was conducted in two orchards in the
Western Cape Province of South Africa. In planta fungicide sensitivity was similar for both
populations, with a shift towards loss of fungicide sensitivity with rare practical cyprodinil
resistance occurring. The average ED50 of one population (sampled year 2006) was estimated to
be at 23μg/ml for cyprodinil and 14.5μg/ml for flusilazole, whereas for the second population
(2010), the ED50 was 24μg/ml for cyprodinil and 19μg/ml for flusilazole. Single-spored isolates
were pre-screened in vitro using a discriminatory value of 0.1μg/ml or 1μg/ml of flusilazole and
0.1μg/ml or 3μg/ml of cyprodinil to compare the relative growth of sensitive vs. resistant isolates.
On average, isolates with shifted flusilazole sensitivity showed an ED50 of 0.036μg/ml. Only 23%
of isolates with a shift in anilinopyrimidine sensitivity were also found to have reduced EBI
sensitivity in vitro. In addition, 20 isolates per orchard were single-spored and tested for mutation
in the ABC transporter gene through PCR-RFLP and sequencing. Polymorphisms potentially
affecting the function of the encoded protein were found in the nuclear binding region of the
ABC 2 transporter.

193-199

5.00 €

 

Organic pome fruit production in Europe and the difficulties in control of fungal diseases
M. Kelderer & D. Gramm

Abstract: Apple and pear production is localized in specific regions within Europe. As different
as their climatic conditions, as special are their production requirements. The severe restrictions
on the use of plant protection products in organic farming imply that not every fruit growing area
is suitable for organic pome fruit production. Considering the susceptibility of different crops and
varieties to fungal diseases is therefore a basic principle for effective organic production systems
in most growing areas. European regulation constitutes the legal framework for the registration of
active substances of plant protection products within the EU, but each substance and commercial
product must then be authorized on a national level. Copper- and sulphur-based products as well
as lime sulphur, used in targeted spray programs, are most commonly applied for the control of
fungal diseases such as apple scab and powdery mildew. In some countries, mainly in the
northern part of Europe, copper and lime sulfur are not registered. In other countries lists of socalled
plant strengtheners, not regulated by the EU and containing active substances with
fungicidal (side) action (for example acid clays, carbonates and phosphonates), exist. At the
moment the continuity of these lists is uncertain. The main fungal diseases, scab (Venturia
inaequalis) and powdery mildew (Podosphaera leucotricha), certainly are a real challenge for
organic pome fruit production, and their biology and control strategies have been studied
extensively and almost exclusively over the last 15 years (MacHardy, 1996; Holb, 2007;
Chapman et al., 2011). However, also the so-called secondary fungal diseases such as alternaria
blotch (Alternaria mali), sprinkler rot (Phytophtora spp.), bull’s eye rot (Pezicula malicorticus),
sooty blotch (complex of different fungi), white haze (Tilletiopsis spp.), etc. (Weber, 2009; Baric
et al., 2010; Mayer et al., 2010), are increasingly becoming of concern. These diseases, with their
origin and development mostly unexplored, used to occur occasionally, but are now appearing
with increasing frequency and intensity. Therefore, an urgent need for the development of new
control strategies against these “new” fungi, compatible with organic farming, exists.

203-211

5.00 €

 

Scab control in organic apple production: conclusions of an eight-year study
in temperate weather conditions

L. Jamar, S. Oste & M. Lateur

Abstract: The objective of this study, conducted over eight growing seasons (2002−2009), is to
identify an innovative way for reducing the use of fungicides and in particular, copper fungicides,
for the control of apple scab (V. inaequalis) in organic apple production. Special emphasis is put
on cultivar traits, sanitation practices and primary scab infection control during spring season. An
original approach is proposed for defining a specific spray timing involving spraying during the
infection processes, especially before fungal penetration, determined by the RIMpro software
warning system. This ‘during-infection’ spray strategy allows reducing from 30 to 50% the
amount of fungicide usually used for effective apple scab control, on high scab-susceptible
cultivars. Potassium bicarbonate, lime sulphur, and three plant extracts such as peel orange
extract, among 60 alternative products tested, have the potential to reduce copper use. However,
copper use, even with low doses, seems to be still necessary in presence of scab-susceptible
cultivars. The results obtained in these experiments could not be attributed to the specific
technical performances of the tunnel sprayer used, which however, offer valuable environmental
benefits. This work shows that (i) planting cultivars with polygenic scab-resistance traits, (ii)
increasing accent on sanitation practices aimed at reducing initial inoculum in autumn, and (iii)
applying an accurate “during-infection” spray strategy in spring, are the three most promising
approaches for substantial further reductions in protection products fully compliant with
international organic crop production standards.

213-221

5.00 €

 

Impact of a cultivar mixture on scab, powdery mildew and rosy aphid in an organic apple orchard
L. Parisi, C. Gros, F. Combe, C.-E. Parveaud, C. Gomez, A. Margueritte & L. Brun

Abstract: The impact of a cultivar mixture within the rows including the cvs Melrouge (low
susceptibility to scab) and Pitchounette (Rvi6 resistant) was assessed during 2008-2009 in an
organic apple orchard located in Rhône Valley (Drôme, France), on three important pests and
diseases: scab, powdery mildew and rosy aphid. In this region, the resistance of Rvi6 gene was
effective since the orchard plantation in 2004. The impact of the cultivar mixture was evaluated
per se, but also associated with sanitation practices to decrease the primary inoculum of scab and
mildew, and compared to disease development on pure stands of Melrouge. The cultivar mixture
showed a good efficiency to decrease the development of scab on leaves and fruits. An important
effect on the number of scab lesions per shoot was observed in 2009 for the cultivar mixture plus
sanitation practices. Our data confirmed the different susceptibility of the 2 cultivars for powdery
mildew. A mixture effect of cultivars was observed in 2008 against powdery mildew. No effect
of sanitation practices was observed. For rosy aphid, a favourable effect of cultivar mixture was
observed in 2008.

223-231

5.00 €

 

Monitoring and prediction models for decision making in plant disease control
V. Rossi

Abstract only

235

0.00 €

 

RIMpro as a practical apple scab management tool
M. Trapman

Abstract only

236

0.00 €

 

Warning system for Nectria galligena during leaf fall
P. F. de Jong & A. Boshuizen

Abstract only

237

0.00 €

 

Development of a pre budbreak climate model to forecast the onset
of Venturia inaequalis ascospore ejection

V. Philion, A. Stensvand, H. Eikemo & D. M. Gadoury

Abstract: Most apple scab fungicides target primary infections caused by ascospores ejected
during rain events. Because ascospore maturation is not always synchronous with host
phenology, ascospore release models may require adjustment at bud break when ascospores
mature early, or when maturation is delayed. In seasons with early ejection patterns, the scab risk
of early infections can be underestimated. Conversely, sprays applied too early during seasons of
late ejection patterns are not useful. Weather conditions during late winter are known to impact
both ascospore maturation and spore production (Philion et al., 2008, 2009). The purpose of our
project was to model shifts in the distribution of ascospore release based on weather, and propose
a method to adjust the biofix for the onset of ejection.

239-246

5.00 €

 

Dynamic release of ascospores of Venturia inaequalis and apple scab disease
control strategy based on the Mills and RIMpro models in Girona (Catalonia-Spain)

P. Vilardell, M. Vilajeliu, L. Batllori & I. Llorente

Abstract: Apple scab is the most important disease on apple production in the North-East of
Catalonia, Spain. In the last 25 years the disease control has been based on fungicide sprays
applied according to the Mills model. From 2004 to present days some trials have been carried
out to validate the RIMpro model in the natural conditions of this geographic area. This paper
show results from trials performed during two years comparing the number of ascospores
discharged predicted by RIMpro forecast system and the ascospores trapped by Burkard sampler.
Results obtained from field trials focused on the control of apple scab by using RIMpro and Mills
predictive models for the primary infections control are also presented. High coincidence
between real ascospores release periods and RIMpro predictions was observed, but in some
periods intensity level differed. The disease control was effective in both predictive models
though less infection warnings and less fungicide sprayings were needed in the RIMpro model
plots.

247-253

5.00 €

 

Postharvest diseases of pome fruits in Europe: perspectives for integrated control
M. Giraud & G. Bompeix

Abstract: In Western Europe, except for some Mediterranean countries, most economic losses
during storage of apples are due to Lenticel spot disease (commonly known as “Gloeosporium
rot”) caused by Neofabraea spp., and superficial scald. With a better knowledge of
epidemiological data of Neofabraea alba, it is possible to reinforce the efficacy of the treatments.
Nowadays, pre-harvest effective chemicals could be fludioxonil, pyrimethanil, boscalid +
pyraclostrobin. Non chemical control is based on hot water postharvest treatment: it has been
shown as very effective not only against both Neofabraea spp. and superficial scald, but also
against Monilia fructigena and Phytophthora spp. Adjunction of formulated clove oil enhances
the efficacy. Hot water treatment now represents a good alternative to chemical postharvest
control and some European companies are selling commercially suitable dipping or drenching
systems. Penicillium expansum is responsible for decays in storage, mainly from airborne
inoculum in cold stores. Sanitation is recommended to avoid infection by Penicillium during
storage; furthermore, certain antagonistic microorganisms (such as Candida spp.) are effective
against P. expansum, Botrytis cinerea and M. fructigena, and are now allowed in some European
countries. With the withdrawal of antioxidants, 1-MCP remains the only available chemical for
postharvest treatment. Its efficacy has been shown against scald, and in addition this product
reduces the incidence of several rots. Among the different modified atmospheres, the most
effective are DCA, ILOS, ULO and extreme ULO. CA with ethylene control could be also
useful. All the above methods of control are discussed in order to combine limited pre-harvest
chemical treatments with alternative methods (integrated control).

257-263

5.00 €

 

Incidence and losses due to fungal rots in cold-stored apples in the UK
A. M. Berrie & K. Lower

Abstract: Fungal rots can result in significant losses in stored apples, particularly in fruit stored
beyond January. Successful control of storage rots depends on a clear understanding of the rots to
be controlled. The objective of this work was to evaluate rot incidence and to assess the success
of the current rot control strategy on commercial farms. Seven pack houses, located in Kent, were
visited weekly from January-March in 2009, 2010 and 2011. Visits were also made to a
packhouse in Hereford. At each visit at least 100 rotted fruit were removed from the rot bin or
collected from the grader of fruit that was being graded at the time of the visit. Rots were
identified visually and numbers recorded. In the survey actual losses due to rots were relatively
low (less than 2% losses overall, range < 0.5-5) in Cox compared to the previous survey in 1995-
2000. Losses in the newer dessert apple cultivars Gala, Jazz and Braeburn were exceptionally
low. Highest losses were recorded in Bramley (on average 1.8%, range < 1-4%), particularly in
the later stored sample assessed in August. Brown rot (Monilinia fructigena) was still one of the
most important rots present. Nectria rot was also causing significant losses. Other rots such as
Colletotrichum sp., Fusarium sp., Botryosphaeria and Phomopsis, present at trace incidence in
1995-2000 survey, have increased in incidence especially on Bramley. Much of the Fusarium rot
on Bramley was associated with core rot. The incidence of Phytophthora rot was higher in 2011,
particularly in the later picked cultivars Jazz and Braeburn, due to above average rainfall from
August – October 2010. The incidence of Gloeosporium in apple samples appears to be
increasing, particularly in the newer dessert cultivars, although actual losses remain low.

265-271

5.00 €

 

Evaluation of treatments to control mouldy core in apples
A. M. Berrie, K. Lower & T. Passey

Abstract: Mouldy core is an internal rot of certain apple cultivars that have an open calyx which
allows saprophytic fungi colonising senescing flower parts to be washed into the core. Fungal
growth then develops within the apple core and eventually rots the apple flesh. Core rots may
also continue to develop in store and may then appear at the cheek, calyx or stalk end of the fruit.
The main problem with mouldy core is that it can remain undetected until the fruit is eaten or
processed. External symptoms in the orchard are rare but fruit may colour and fall prematurely.
In the UK the problem is mainly associated with the cultivars Cameo and Bramley’s Seedling.
The objective of the work described was to identify core rot incidence and the main fungi
responsible for the problem in Cameo and Bramley in the UK and to identify effective fungicide
programmes to control them. The incidence of core rots was greater in 2009 than 2008 or 2010 in
both Cameo and Bramley and in general more core rots were found in fruit that had dropped from
the tree than in fruit sampled from the tree. The main fungi identified included Fusarium spp,
Alternaria spp. and Penicillium spp. Colletotrichum was also important on Bramley but not
Cameo. In 2009 and 2010 trials were established in Cameo and Bramley orchards located in Kent
to evaluate the efficacy of fungicide products against mouldy core. The results indicated that both
Bellis (pyraclostrobin + boscalid) and Switch (cyprodonil + fludioxonil) have some effect on
reducing mouldy core when applied during blossom and petal fall but Systhane (myclobutanil)
mixed with Scala (pyrimethanil) was ineffective.

273-281

5.00 €

 

Influence of stress treatments on the infection risk for Botrytis cinerea on apple
T. Vanwalleghem, W. van Hemelrijck, T. T. A. Bui, M. Hertog, B. Nicolai, M. Davey, W. Keulemans & P. Creemers

Abstract: In Europe the pome fruit growing industry is currently confronted with residue
restrictions imposed by marketing chains as retail companies and import countries. Next to a high
quality product also a limited residue loading on the fruit surface is requested. Mostly the
chemical fungicides applied shortly before harvest towards fruit rot decay during storage are
focused as they are frequently detected after analytical analysis. The past years research
concerning alternative approaches has exploded. In line of this topic, an IWT-project
(IWT070573): “Engineering of the antioxidant metabolism in apple fruits for a less sensibility of
storage diseases and a higher nutritional value” has started. During this project the relationship
between different cultivars, pre- and post-harvest stress treatments, harvest time, antioxidant
metabolism and the resistance against pathogen infections in function of the storage time will be
investigated. Until now the effect of some cultural and physical measurements on the
susceptibility of different cultivars for Botrytis cinerea was evaluated. The results show that there
is a clear difference in susceptibility to B. cinerea between different cultivars: Braeburn and Fuji
are the most susceptible. The effects of the different pre-harvest stress treatments differ between
the cultivars. Furthermore the B. cinerea infection progressed more rapidly on the shadow-side of
the fruits compared to the sun-side. The results from this project can lead to an alternative
approach for the chemical disease management of Botrytis cinerea in the field.

283-293

5.00 €

 

The response of antioxidant metabolism in apple fruit to post-harvest storage disease Botrytis cinerea
B. T. A. Tuyet, T. Vanwalleghem, B. Vorstermans, P. Creemers, M. Hertog, B. Nicolai, J. Keulemans & M. Davey

Abstract only

294

0.00 €

 

Management of postharvest decay in South African Forelle pears
P. J. van Rensburg & C. L. Lennox

Abstract: Postharvest losses due to decay can be significant in South African Forelle pears
destined for export markets. In order to develop a decay management strategy, bloom and
postharvest fungicide applications were evaluated for their efficacy in reducing decay in fruit
from three commercial Forelle orchards. Iprodione and benomyl were applied at full bloom and
75% petal drop, and procymidone at full bloom. Iprodione, pyrimethanil + imazalil, pyrimethanil
and the biological control agent Cryptococcus albidus were applied as postharvest dip treatments.
Control fruit were treated with water. Fruit were stored at -0.5°C regular atmosphere for 14
weeks, ripened at 21°C for 7 days and then evaluated for decay. In the control treatment, calyx
end decay (CED) incidence was significantly higher in orchard three only. Iprodione, benomyl
and procymidone, applied at bloom significantly reduced CED in this orchard, while benomyl
significantly reduced CED in orchard one. None of the postharvest treatments significantly
reduced CED caused by Botrytis cinerea. Iprodione significantly reduced decay caused by
Alternaria in orchard one when compared to the control. The postharvest treatments reduced
decay caused by other minor pathogens when compared to the control fruit in this orchard. Decay
from orchards two and three was not significantly reduced by any of the postharvest treatments.
Cryptococcus albidus did not significantly reduce decay in Forelle pears for all orchards.

295-300

5.00 €

 

EUFRIN Working Group: Sustainable fruit production to minimize residues
F. Zavagli

Abstract only

303

0.00 €

 

Five years experience in the residue free production of Conference
M. Polfliet, H. Balkhoven & E. Elias

Abstract only

304

0.00 €

 

Hot water treatment – a physical method to reduce post-harvest diseases of fruit
B. Trierweiler, H. Schirmer & S. Kulling

Abstract only

317

0.00 €

 

Current status of sanitation and new roles in apple scab management
W. MacHardy

Abstract: Sanitation is recommended in all apple scab IPM programs, but growers consider
sanitation optional rather than indispensable. A review of studies that investigated the
effectiveness of urea and shredding the leaf litter to reduce ascospores, the major source of
primary inoculum causing apple scab, has led to a prediction that, in routine practice, applying
5% urea to trees after harvest and shredding the leaf litter in spring will reduce the ascospore
dose approximately 70%. These combined practices are required in a New Hampshire (NH)
Sanitation Program that significantly reduces fungicide in a low-scab-risk orchard by leaving
early-season infection periods unprotected. Sanitation has two clearly-defined roles that make it
indispensible to the program’s success: sanitation (1) compensates for errors in an autumn foliar
scab assessment that identifies an orchard’s level of scab-risk next season and (2) reduces the
potential for an unacceptable buildup of scabbed fruit in a low scab-risk orchard that leaves earlyseason
infection periods unprotected. For decades, chemicals, machinery, and biological agents
have been screened to determine their effectiveness in reducing the ascospore dose. Screening to
identify sanitation practices that will reduce the ascospore dose > 90%, in routine practice, should
continue because this will optimize the roles of sanitation in scab management, but the NH
sanitation program demonstrates that the goal of sanitation, i.e. integrating sanitation into a scab
management program to reduce the fungicide dose, can be achieved with the efficiency of
sanitation practices available now.

319-330

5.00 €

 

Orchard sanitation as a management approach to control apple scab in South African apple orchards
S. G. von Diest, J. C. Meitz & C. L. Lennox

Abstract: South African apple producers use 6-15 fungicide sprays per season to control apple
scab, caused by Venturia inaequalis (Cke.) Wint. However, despite the availability and use of
effective fungicides, severe losses to scab are regularly sustained in South African apple
orchards. The global trend towards integrated management of scab and reducing reliance on
agricultural chemicals, as well as the urgent need for expertise on scab in South Africa, prompted
the initiation of this project. The aim of this project is to compare the efficacy of sanitation
strategies with conventional chemical strategies in reducing scab incidence and severity in South
African apple orchards. This is the first commercial-scale study on the use of orchard sanitation
to control scab in South Africa. Using a randomized block design, six treatments were replicated
three times, with three orchards each acting as a block. The treatments were: leaf removal; leaf
shredding; postharvest urea sprays at 70% and 100% leaf drop, an integrated treatment that
combined leaf-shredding and urea; a non-sanitized/non-sprayed negative control, and a nonsanitized
positive control sprayed according to guidelines in a standard scab fungicide
programme. Treatment effect on fruit and leaf incidence and severity were not statistically
different from controls, with the exception of leaf shredding, which was 15% lower than in the
negative control in November 2010. Why treatments were not more effective in reducing scab
incidence and severity is discussed.

331-336

5.00 €

 
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