Grape Diseases Menagment in Canada

8/9/2019 Grape Diseases Menagment in Canada

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Grape disease management

in Quebec


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Grape diseasemanagement

in Quebec

Odile Carisse, Ph.D.

Agriculture and Agri-Food Canada

In collaboration with:

Rjean Bacon, M.Sc.


Jacques Lasnier

Co-Lab Recherche & Dveloppement

Annie Leebvre, Audrey Levasseur,

Daniel Rolland and Tristan Jobin


Her Majesty the Queen in Right o Canada, 2009

Aussi oert en ranais sous le titre :Gestion raisonne des principales maladies de la vigne au Qubec

AAFC Number 10372ECatalogue Number A52-146/2009E-PDFISBN 978-1-100-12957-0

SPCS (S. Hindson)


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Grape disease management in Quebec

In Quebec, grapes are aected by several diseases,

including root, wood, leaf and berry diseases.

The most prominent are downy mildew, powdery

mildew, Botrytis bunch rot, anthracnose, black rot

and crown gall.

The purpose o this guide is to acilitate the decision-

making process for growers and consultants indealing with disease management. Choosing

the appropriate control strategy must take into

account a combination o actors that will allow

the rational use of fungicides, while respecting

the environment.


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Table o contents

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

Disease management strategies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Rational grape disease management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Preventing diseases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Data collection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Fungicides: mode o action and their mobility in the plant . . . . . . . . . . . . . . . . . . . .11

How to use ungicides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

Fungicide efcacy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Practical questions related to ungicides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

Grape diseases scouting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Major grape diseases ound in Quebec . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Downy mildew Plasmopara viticola . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Downy mildew disease cycle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Downy mildew management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Downy mildew management in brie . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

MILVIT approach to downy mildew management . . . . . . . . . . . . . . . . . . . . . . . .22

Powdery mildew Erysiphe necator (Uncinula necator) . . . . . . . . . . . . . . . . . . . . . . . 23

Powdery mildew disease cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Powdery mildew management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Powdery mildew management in brie . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Powdery mildew management based on disease risk estimations. . . . . . . . . . .27


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Table o contents (contd)

Bunch rot, grey mold Botrytis cinerea . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28

Bunch rot disease cycle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Bunch rot management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30

Bunch rot management in brie . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Anthracnose Elsinoe ampelina. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32

Anthracnose disease cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Anthracnose management. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Anthracnose management in brie . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Black rot Guignardia bidwellii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

Black rot disease cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Black rot management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38

Black rot management in brie . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Crown gall Agrobacterium vitis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40

Crown gall disease cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Preventive measures or crown gall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

Crown gall management strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

Ackwledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Phenological stages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44


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Introduction

Conventional strategies or grape disease management are basedon routine applications o ungicides. These scheduled ungicidespray programs are based on grape phenological stages andthereore do not take into consideration disease pressure andweather conditions.

This approach can lead to the overuse o ungicides which canincrease arm input expenses and added environmental stress.Frequent ungicide applications may not be required everyyear, especially when disease incidence is below the economicthreshold and when taking into considerations other actors suchas cultivar susceptibility and disease presence.

Monitor elds or diseaseRegular and requent eld scouting is the oundation o inte-grated disease management. However, scouting should be doneat the right time, mostly beore the critical periods or diseasedevelopment. The inormation obtained must be recorded oruture reerence because they will be useul in planning control

strategies in subsequent years (see : http://www4.agr.gc.caAAFC-AAC/display-acher.do?id=1210281691267&lang=eng)Crop scouting allows or early disease detection, ideally, beorethe economic threshold is reached, this way, unnecessarily un-gicide applications can be avoided.

Rational disease management: step by step

Rational disease management should be gradually integratedinto the growers practices. Management tools proposed in thisguide dont have to be adopted all at once. Growers may start byimplementing sanitation practices which will help reduce diseasepressure. Later, disease monitoring may be introduced; this wilallow ungicide timing based on disease risk rather than at xed-intervals. Ultimately, ungicide applications could be based onboth scouting and disease orecasts. This guide provides the keyelements necessary to achieve a rational approach to diseasemanagement or the main diseases ound in Quebec.

Conventional pest management Rational Pest management

Easier More complex

Risk o ungicides overuse Optimal use o ungicides

Steps to integrated pest management

Fungicide

use

Fongicide

us

e

Fungicide

only Prevention

Prevention

Scouting

Prevention

Scouting

Forecasting models

6
http://www4.agr.gc.ca/AAFC-AAC/display-afficher.do?id=1210281691267&lang=enghttp://www4.agr.gc.ca/AAFC-AAC/display-afficher.do?id=1210281691267&lang=enghttp://www4.agr.gc.ca/AAFC-AAC/display-afficher.do?id=1210281691267&lang=enghttp://www4.agr.gc.ca/AAFC-AAC/display-afficher.do?id=1210281691267&lang=eng


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Disease management strategies

Calendar-based ungicide scheme

Fungicides are applied according to the vine growth stages(phenological stages). Basically, ungicides rom dierent chem-

ical amilies are alternated and applied based on manuacturers

recommendations (label). In Quebec, growers mostly use the un-

gicide spray calender provided in the Ontario Ministry of Agricul-

ture publication Fruit Production Recommendations (publication

360). This ungicide scheme is based on a complete protection o

the vines rom the beginning o fowering to veraison.

Advantages The ungicide scheme is simple, almost identicalevery year and growers know in advance how many sprays andwhen ungicides will be applied.

Disadvantages Some sprays may not be needed i the dis-ease is absent or in small amounts. Timing o ungicide spraysmay not be optimal and hence ungicides less ecient. This typeo ungicide scheme oten leads to the over use o ungicides,consequently increasing input expenses and can have a nega-tive aect on the environment. This strategy may promote thedevelopment o ungicide resistance in pathogen populations.

Rational disease management

Fungicide applications are based on disease risk estimates suchas cultivar susceptibility, current and previous disease scoutingrecords, phenological stages, weather conditions, time elapsedsince the last ungicide spray and vine growth rate.

Advantages Fungicide ecacy is optimal, number o ungi-

cide sprays may be reduced depending on year, consequentlyreducing the cost o disease management and the risks o de-veloping ungicide resistance within pathogen populations whencompared to xed-interval ungicide spray programs.

Disadvantages More complex than xed-interval spray pro-

grams. This type o management scheme requires more eorrom the grower and requires that the grower be able to toleratesome level o disease risk. Disease monitoring and weather datamust be available.

Integrated Disease Management

This program is based on the integration o dierent methodso disease control including biological, cultural, and chemicacontrol. The methods could be preventive (sanitation) or reactive(rational use o ungicides). This program requires good plan-ning, starting beore vineyard establishment. This managemen

program is largely based on prevention including the selectiono vineyard site, row orientation, choice o cultivars, plantingdensity, pruning

Advantages Fungicide ecacy is optimal, number o ungi-cide sprays may be reduced depending on year, consequentlyreducing the cost o disease management and the risks o de-veloping ungicide resistance within pathogen populations whencompared to xed-interval ungicide spray programs. Diseasecontrol is stable over years.

Disadvantages More complex than xed-interval spray pro-

grams. This type o management strategy requires substantia

amounts o knowledge in disease management practices and un-

gicides (mode o action, ecacy...). Growers must also be able to

deal with some level o disease risk. Disease monitoring, weather

data and inormation on disease management must be available.

Integrated Disease Management systems

are largely based on prevention.

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Rational grape disease management

Objectives

Spray only when needed: the disease is present, weatheri avourable and the cultivar is susceptible.

Protect the natural micro-auna present in the vineyard:do not use ungicides that aect predatious mites.

Limit ungicide residues on berries by respectingrecommended pre-harvest delay.

Avoid development o ungicide resistance in the pathogenpopulations by alternating ungicides rom dierentchemical groups and by spraying only when necessarily.

Ensure the security o the workers responsible orungicide applications and those working in the vineyard.

Reduce environmental impact by selecting ungicideswith low toxicity.

Maintain grape quality and yield over the years.

Reasoning disease management

Beore applying a ungicide, make sure that preventive measureswere implemented. Preventive measures allow a reduction indisease pressure and consequently reduce the need or ungicide

sprays and increase ungicide ecacy.

Key elements or reasoning disease management

A good knowledge o the pathogens biology. Regular and requent disease monitoring or proper timing

o ungicide sprays and selection o the right ungicide.

A good knowledge o ungicides registered or use ongrapes including mode o action, absorption by the plant,rate, ecacy, requency, persistence, pre-harvest interval,negative eects, toxicity, and tank mix compatibility withother pesticides.

Ideally, a good understanding o orecasting systems orother management tools such as spore samplers.

Denitions

Action threshold: Disease level observed in the vineyard abovewhich the cost o yield losses is expected to be greater than thecost o a ungicide spray. In other words, it is more cost-eectiveto spray than to let yield losses occur, however, i disease level isbelow the action threshold it is not cost eective to spray.

Forecasting models (decision-making tool): Forecasting mod-els are a mathematical representation o disease development

Model outputs are generally an estimate o disease risk and areused in conjunction with eld scouting observations.

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Preventing diseases

Beore planting

Site selection: Choose a site with good water drainage and goodair circulation.

Row orientation: I possible, row orientation should be south-eastor south-west to maximize air circulation and sunlight exposer.

Choice o cultivars: I possible, choose cultivars that are less sus-ceptible to diseases (see Internet guide at : http://www4.agr.gc.ca/

AAFC-AAC/display-acher.do?id=1210281691267&lang=eng ;Appendix 1).

Planting density: Choose a training system and a planting dens-

ity (plant spacing) which avour good air circulation and reducesthe occurrence o prolonged lea and berry wetness periods.

Perennial cover crops and plastic mulches: Choose slowgrowing grasses without rhizomes such as escue. Use goodquality plastic mulches.

Mature Vines

Soil: Working the soil in the spring is a orm o cultural controlDestroy and burn inected debris to reduce pathogen populationsat the start o the season, thereore reducing the risk o disease

Weed management: Maintain good weed control to avoid

excessive humidity in the lowers parts o the vines and to reducecompetition or nutrients and water.

Fertilization / irrigation: Make sure nutrient levels are adequatebut avoid the excessive use o nitrogen ertilizers which promoterapid growth and hence the production o young leaves that aremore susceptible to some diseases. It might be necessary to

irrigate young plants in vineyards planted on sandy soils.

Canopy microclimate: Manage the canopy (pruning, lea re-moval, shoot topping and positioning) so that it improves aircirculation to promote rapid drying o oliage and help shortenthe duration o wet periods. Proper management will allow orbetter ungicide penetration into the canopy.

Grape pruning: Canes letover rom pruning may act as a res-ervoir or inoculum, when possible burn them or at least removerom the vineyard.

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Data collection

Weather data

When possible, collect basic weather data such as air temper-ature, relative humidity and rainall (duration and intensity) in yourvineyard. I you dont have an on-site weather station, use theinormation provided by Environment Canadaor your region .

The main reason or collecting weather data is to estimate dis-ease risk. The inormation gathered is used as input by mostdisease orecasters to estimate disease risk. Keeping accuraterecords throughout the years will provide the grower with addi-tional inormation. For example, it is possible to calculate growingdegree days rom temperature data, which in turn can predictthe occurrence o specic phenological stages, harvest dates and

critical periods with regards to disease.

Biological data

Disease monitoring data is the key element o disease manage-ment. It is essential to keep records o scouting data.

Field scouting orms should include:

Date o observation, cultivar and vineyard section

Phenological stage

General appearance o the vines

Symptoms: description and location on the vine, theirseverity (number or proportion o vines, shoots, leaves orberries diseased) draw on outline o the eld and mapout the area where symptoms are present

Sprays: kept track o ertilizer and pesticide applicationsthroughout the season

The decision process

The decision to apply a ungicide will depend on:

Presence or severity o damages(example: 1, 5 10, 25, 50 or > 50% organs diseased)

Cultivar susceptibility (see: http://www4.agr.gc.ca/AAFC-AAC/display-acher.do?id=1210281691267&lang=eng;Appendix 1)

Disease history (try to identiy problem spots byreviewing disease history or each section o thevineyard): is the disease chronic or does it reappearone year out o every two to ve years?

Phenological stage: beore, beginning or ater fowering

Time elapsed since the last ungicide spray and ungicidepreviously used

Forecast weather data or the next ew days

Regional warnings, when available

10

It is possible to calculate growing degree

days rom temperature data, which in turn

can predict the occurrence o specifc

phenological stages, harvest dates and

critical periods with regards to disease.


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Fungicides: mode o action and their mobility in the plant

Mode o action

Fungicide modes o action can be divided in two categories:single-site and multi-site.

Single-site ungicides target a specic unction o ungal de-velopment, and this opens the door to resistance development.Just one mutation on the target site or any other means oavoiding or countering the eect o the ungicide can lead to asignicant loss o ecacy o the ungicide. Biosynthesis o com-pounds essential to the development o the ungus, respirationand cellular division are the most common targets o single-siteungicides.

Amulti-site ungicide acts on several unctions o ungus de-velopment. They are less prone to resistance development be-

cause mutations in the ungus must occur at all target sites or

resistance to develop. Most contact ungicides that are applied

pre-inection such as Mancozeb, Captan, as well as elemental

ungicides like copper and sulphur, are members o this category.

Mobility in the plant

Once applied on a plant or in the soil, ungicides either stay onlea surace or penetrate in the plant.

It is possible to distinguish between two main ungicide typesFungicides not absorbed by the plant, called contact ungi-cides or protectants, and ungicides absorbed by the plant.

There are three types o ungicides absorbed by the plant:

Local systemic or translaminar(across the lea blade)

Systemic with ascendant diusion(xylem-mobile)

Completely systemic(ascendant and descendant diusion)

Contact or surace ungicide not absorbed by the plant

11

Germination stopped

Spore

Upper surfaceFungicide

Vascularplant tissues

Underside surface

Leaf

Possible space between drops = incomplete coverage

Fungicide


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Systemic or trans-laminar ungicide

Completely systemic ungicide

12

Growth and sporulation stopped

Spore


Vascular

plant tissues

Underside surface

Leaf

Possible space between drops = incomplete coverage

Fungicide

Growth and sporulation stopped

Spore


Vascular

plant tissues

Underside surface

Leaf

Space between drops always filled up = complete coverage

Fungicide


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How to use ungicides

Better knowledge or better ecacy

When contact ungicides are applied, droplets will spread on leasurace but will not penetrate into the plant. Leaves or other plant

parts that emerge ater the ungicide application are not protected

by the ungicide. Contact ungicides are washed o by rain and

degraded by sunlight. Examples: Polyram, captan, copper.

When local systemic ungicides (translaminar) are applied,droplets spread and penetrate into the leaves under the cuticleat the point o entry. The ungicides will stay near the point oentry and do not circulate in the plant; hence leaves or otherplant parts that emerged ater the ungicide application are notprotected by the ungicide. Ater penetrating into the plant these

ungicides, are not washed o by rain or degraded by the sun.Examples: Nova, Sovran.

Completely systemic ungicides can be applied onto either theoliage or the soil. Once the ungicide is absorbed by the plant, itwill move upwards or downwards throughout the plant. Leavesor other plant parts that emerged ater the ungicide applicationare protected by the ungicide but the ungicide is diluted by theplant growth (more leaves or the same amount o ungicide).Example: Ridomil.

Preventive or reactive strategy

Preventive strategy (pre-inection): Fungicides are applied be-ore an inection period with the aim o preventing inection. The

ungal pathogen is killed beore it penetrates into the plant or dur-

ing early stages o ungal development such as spore germination

Reactive strategy (post-inection): Fungicides are appliedsoon ater an inection period with the aim o controlling an inec-tion that has already occurred. These ungicides have an eecton more advanced stages o ungal development and stop ungacolonization in the plant. This approach is eective against nonorecasted inection, severe inections and under requent rainyperiods (ungicides used in post-inection are less prone to wash

o by rain).

Fungus: Pre-inection and post-inection

13

Pre-infection

(Protectant)

Protection /

inoculum dispersion

Post-infection

(Curative)

Inoculum

dispersion

Contamination /

inoculum production


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Fungicide efcacy

Key elements or ecient chemical control:

Apply ungicide based on disease risk, time elapsedsince last spray, and weather conditions.

Choose ungicide based on disease risk, absorbtionby the plant, strategy (pre- or post-inection) andanti-resistance program (alternate ungicides romdierent chemical group).

Use the recommended rate and careully preparespray solution.

In general contact ungicide are washed o by 25 mm or more o

rain or irrigation water (see diagram below).

Several actors are responsible or reduced ungicide ecacyuse o inappropriate ungicide, miscalculation when preparingspray solution, water pH, poor sprayer calibration, bad timingand environmental conditions during treatment application andungicide resistance. In general, ungicide resistance is not themain actor or poor ungicide ecacy; however, resistance tosome ungicides has been reported in some Quebec vineyards.

Fungicide resistance is a natural phenomenon in which somemembers (spores) o the ungal population are capable o re-sisting the detrimental eect o ungicides. These individuals wiltransmit their resistance to their progeny. Ater being subjectedto several ungicides sprays, the proportion o resistant individ-

uals may reach high levels leading to disease control ailure. Thenumber o sprays necessary to achieve a shit in control ecacyvaries according to ungicide use and initial composition o thepopulation when the ungicide is rst used.

Foliage protected by the fungicide Foliage not protected by the fungicide

Efficacy

100 % -

0 % -Days after treatment

7100

100 % -

Efficacy

0 % -Days after treatment

7100

10 mm of rain

25 mm of rain 15 mm of rain


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Practical questions related to ungicides

Preventive eect: Destruction o the ungus beore its penetra-tion into the plant.

Curative eect: Destruction o the ungus ater its penetrationinto the plant (ater inection has occurred). Duration and ecacyo curative eect vary among ungicides.

Anti-sporulation eect: Destruction o ungal reproduction(sporulation) ollowing an inection.

Fungicide: Phytosanitary product developed to kill or limit ungalplant pathogen development.

Absorbed ungicides: Fungicides that are absorbed (are takenup) by the plant, they may or may not be redistributed in theplant. These ungicides are not washed o by rain or irrigationwater once they have penetrated into the plant.

Systemic ungicides: Fungicides that are absorbed by the plantand redistributed into the plant vascular system. The ungicideRidomilis absorbed by the grape leaves and redistributed to newleaves and clusters during period o rapid growth. Fungicide re-distribution to cluster is reduced ater ruit set.

Lea wetness: Presence o ree water on lea, shoot or ruitsurace. In general ungicides applied to wet oliage are dilutedmaking them less ecient.

Wetness duration: Length o time in hours during which leavesshoots or berries are wet. The duration o wetness is oten usedin orecasting systems to estimate the risk o inection andsporulation.

Primary inection: Inection caused by spores that over-wintered or that where produced in ruiting bodies that haveover-wintered. These inections are generally the rst inectionsoccurring in the spring.

Secondary inection: Inection caused by spores produced onlesions or other symptoms induced by primary inections. Theseinections are responsible or disease development during thesummer months.

Phytotoxicity: Properties o certain phytosanitary products suchas ungicides that cause injury to plants, examples are distortionstunting or burning o plant parts. These alterations can have atemporary or permanent eect on plant growth.

Phytosanitary product: Related to plant protection. They are

active substances or chemical compounds developed to contropests including disease, insects and weeds.


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Grape diseases scouting

DISEASE

START

SCOUTING SAMPLE SIZE WHAT TO LOOK FOR REMARKS

DOWNY MILDEW

Stage 7 Minimumo 25-50 vinesSusceptiblecultivars

Yellowish discolorationmore or less circular.White down mainly on thelower lea surace.

Start scouting on the mostsusceptible cultivars and areaswith poor air circulation.

Apply a ungicide immediatelyi symptoms are detected.

POWDERY MILDEW

Stage 7 Minimumo 25 vines

Susceptiblecultivars

Yellowish discolorationollowed by a thin white

powdery layer.

Pay attention to leaves inside thecanopy (in shaded areas).

BUNCH ROT

Stage 19-21

Stage 35

Minimumo 100 fowers

100 clusters

Blighted and / or witheringinforescences. Brownberries that turnedreddish. Berries coveredwith a grayish mold.

Careully write down weatherconditions during fowering eveni symptoms are absent.

ANTHRACNOSE

Stage 7 Minimum

o 20-25 vinesSusceptiblecultivars

Minute black spots

on leaves, petiolesor berries.

Start scouting as early as

possible and spray as soonas symptoms appear.Spray preventively on highlysusceptible cultivars.

BLACK ROT

Stage 7 Minimumo 25 vinesSusceptiblecultivars

Brown spots on leaves.Upper part o berries arebrown and sunken.

Start scouting as early aspossible and spray as soonas symptoms appear.

CROWN GALL

Stage 3 All vines, at leastonce per season

Galls at the baseo the vine.

Destroy inected vines.Some cultural practices suchas pruning may avour bacterialdissemination.

For more inormation on grape diseases scouting, see:

http://www4.agr.gc.ca/AAFC-AAC/display-acher.do?id=1210281691267&lang=eng
http://www4.agr.gc.ca/AAFC-AAC/display-afficher.do?id=1210281691267&lang=enghttp://www4.agr.gc.ca/AAFC-AAC/display-afficher.do?id=1210281691267&lang=eng


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Major grape diseases ound in Quebec

Grapes are highly susceptible to several diseases. In

general, i no control measures are used (biological

or chemical), yield losses are signifcant and grape

production unproftable.

Downy and powdery mildews, bunch rot, anthra-

cnose, black rot and crown gall are the most

common diseases. All these diseases are caused

by ungi with the exception o crown gall, which

is caused by a bacterium. These diseases

can decrease yields and grape quality. (http://

www4.agr.gc.ca/AAFC-AAC/display-aicher.

do?id=1210281691267&lang=eng).
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18/47

1818

Downy mildew Plasmopara viticola

Grape downy mildew is native to North America and aects

most species o the Vitisgenous but viniferacultivars are

highly susceptible. The degree o susceptibility to downy mil-

dew varies between cultivars.

Downy mildew can inect shoots, leaves as well as fower

and ruit clusters. In addition to direct damage on berries,

downy mildew can cause premature lea all which delays

ruit ripening and increases susceptibility to winter damage.

Symptoms

The pathogen can inect all green parts o the vines. First symp-toms are light green or yellow spots, commonly reerred to asoil spots because o their greasy appearance. Under warmand humid conditions, white, fuy sporulation develops on thelower surace o the lea. As lesions age, they turn brown andthe inected tissue dies, sporulation becomes greyish and leavesmay all. Inforescences are highly susceptible to downy mildew,ollowing severe inection they turn yellow, than brown and dryup. White spore masses develop on inected ruit clusters whichcauses inected berries to turn blue, than brown and wither.


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B C

A A

1919

Downy mildew disease cycle

Winter The ungus overwinters as spores (oospores) in deadleaves on the vineyard foor. These spores can survive cold tem-peratures as low as -26 C, but they are less likely to survive ithey are covered with soil (or buried). (A)

Spring Spores that survive the winter (oospores) germinate inwater when temperatures reach 11 C, and produce sporangiumwith in turn liberate a new type o spore called zoospore. Thesezoospores move in water and spread to new shoots and newleaves by wind and rain. These spores are responsible or primaryinections, they inect lea tissue by swimming to the vicinity ostomata where they germinate and enter inside the lea. Underoptimal conditions, at temperatures o 18 - 25 C, the inection

can takes place within 90 minutes. (B)

Summer Following the primary inections, the ungus growswithin the tissues and produces new spores (sporangia con-taining zoospores). Sporangia are spread by wind and rain ontoshoots, leaves, fowers and berries where they cause secondaryinections.

Optimal conditions or secondary inection are: wetness durationso at least 4 hours under darkness, 95 - 100 % relative humidityand temperatures between 18 and 22 C. New spores will beproduced on new lesions and cause new lesions and so on. Le-sions appear within 5 to 17 days ater inection and this cycle wilcontinue as long as the conditions are avourable. (C)

Fall The ungus produces survival spores (oospores) in deadgrape leaves. (A)


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2020

Downy mildew management

Susceptibility Vines are susceptible rom the appearance othe rst lea (growth stage 7) up until approximately 3 weeksater fowering, when young grapes loose their susceptibility.However, rachises remain susceptible.

Critical period From the rst unolded lea (stage 7) to verai-son (stage 35). In general mildew appears in early summer andreappears near harvest on regrowth.

Primary inections They occur in the spring while rainfall

is more than 2 mm on humid sol at temperatures of 11 C or

higher.

I these conditions occur, start scouting in the vineyard and applya ungicide i symptoms are present.

Secondary inections They are avoured by rainy weatheconditions, thereore i the requency o rainall increases so doesthe risk o inection. So the decision to treat with a ungicideshould be based on scouting results (presence or absence olesions) and rainall requency. Lesions appear 1-2 weeks aterrain; making it possible to adequately time ungicide sprays andto evaluate the ecacy o the treatment. For highly susceptiblecultivars, ungicides maybe applied preventively.

Management strategy The strategy or downy mildew man-agement is based on a good control o lea inections beore thecritical period in order to avoid berry inections as much as pos-sible. Under severe epidemics, spray treatments targeting berry

protection may be needed.

Tip The 10 - 10 -10 rule to decide when to start scouting ordowny mildew: the shoot growth exceeds 10 cm, there has been10 mm o rainall and temperatures have been at least 10 Cduring a 24-hour period.

Start scouting or downy mildew when the shoot growth exceeds10 cm, there has been 10 mm o rainall and temperatures

have been at least 10 C during a 24-hour period.


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2222

MILVIT approach to downy mildew management

MILVIT or Mildew and Viticulture was developed in Europe. Ituses disease risk indicators to predict inections o downy mil-dew and generates warnings to assist growers in taking day today decisions to manage downy mildew. Disease monitoring isthe key element o MILVIT. Scouting is initiated as soon as therst leaves emerge in the spring (stage 7). Daily monitoring oweather conditions is initiated when the rst lesion is detectedin the vineyard.

I 5 - 10 mm o rain are expected and temperatures are above12 C, a ungicide application is required to protect new growth.

Ater the rst application, keep monitoring the vineyard or symp-toms. As soon as new lesions are detected, an another ungicide

application is needed i 5 - 10 mm o rain are expected and temperatures are above 12 C.I rain events are requent, making it dicult or ungicide ap-plications, a systemic ungicide may be used. The only systemicungicide registered or use on grape is Ridomil. I this occurs aterfowering (post- bloom) a protective ungicide may be applied.

Frequency o applications thereater depends on the same cri-teria (symptoms and 5-10 mm o rain when temperatures areabove 12 C). From ruit set to harvest, the berries are less sus-ceptible to downy mildew, hence i berries are not diseased, it is

acceptable to tolerate some downy mildew on leaves.

It is important to scout until harvest because the amount o in-oculum present on the leaves at lea all will be responsible ornext years primary inection. This will allow a better preparationo next years control strategy.

It is important to scout until harvest

because the amount o inoculum present

on the leaves at lea all will be responsible

or next years primary inection.


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2323

Powdery mildew Erysiphe necator (Uncinula necator)

Grape powdery mildew, caused by the ungal pathogen

Erysiphe (Uncinula) necator is native to North America.

Powdery mildew is present in almost all vineyards and may

signicantly reduce yields and grape quality. Susceptibility to

powdery mildew varies between cultivars, however most cul-

tivars grown in Quebec are susceptible. All aerial plant parts

could be inected and yield losses vary rom year to year.

Symptoms

The powdery mildew ungus can inect all green tissues. Onleaves, rst symptoms are whitish gray, dusty or powdery le-sions. Severely inected leaves may wither or curl then all onthe ground.

On shoots, inections may cause star shape lesions which turndark brown with age. Inected berries are grayish and dusty, maycrack, dry o and all on the ground.

Inected berries become whitish gray with a dusty or powdery ap-pearance. Severe berry inections can result in splitting o berries.

At the end o the season, the ungus produces small golden-brown to black ruiting bodies (cleistothecia) on inected plantparts. The cleistothecia overwinter in bark crevices o the vine.


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C

B

AA

BC

2424

Powdery mildew disease cycle

Winter The ungus overwinters in bark crevices o the vine inthe orm o a ruiting body (cleistothecia).(A)

Spring As temperature increases cleistothecia mature and re-lease ascospores that are disseminated by wind and rain. Oncethese spores are deposited onto the leaves or other green tissues,they germinate and cause the primary inections. Leaves locatednear the bark tend to get inected rst. Optimal conditions orprimary inections are the presence o rain and temperatures o20 C or higher. (B)

Summer New spores (conidia) are produced on inected organsThese spores are wind-disseminated and cause the secondaryinections. From new lesions, new spores are produced, thesespores will then produce new lesions rom which will appear newspores so on and so orth. Under optimal conditions this cycletakes approximately 5 - 6 days. (C)

Fall Cleistothecia are produce in late summer during themonths o August and September. Once they have matured cleis-tothecia detache rom leaves, shoots and berries and only theones that all into bark crevices can survive over the winter. (A)


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2525

Powdery mildew management

Susceptibility Leaves are susceptible to powdery mildew assoon as they emerged (stage 7). Berries are susceptible rominitiation to veraison.

Critical period From 4-6 unolded leaves (stage 12) to verai-son (stage 35). In general, powdery mildew appear beore thebeginning o fowering and progress until late all.

Primary inections They occur in the spring i rainall exceeds2.5 mm or at least 4 hours, when temperatures are between6 and 24 C. When these weather conditions arise survey thevineyard or symptoms o powdery mildew and initiate ungicidesprays i lesions are detected.

Secondary inections Optimal temperature or inection is23 C (20-27 C). Inection can occur when relative humidity o40 % or higher; however spore (conidia) germination is inhibitedby the presence o water. Light may also inhibit spore germina-tion; hence, powdery mildew generally develops inside the can-opy (IMPORTANT FOR SCOUTING).

Management strategy The strategy or powdery mildew man-agement is based on a good control o lea inections beore thecritical period in order to avoid berry inections as much as pos-sible. Under severe epidemics, sprays that target berry protection

may be needed.

MEAN AIR

TEMPERATURE

(C)

TIME REQUIRED TO COMPLETEAN INFECTION CYCLE, FROM

INFECTION TO SPORULATION

(DAYS)

6 32

9 25

12 18

15 11

17 7

23 6

26 5

30 6


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2626

Powdery mildew management in brie

SPRAY TIMING REMARKS CRITERIA FOR DECISION

BEGINNING OF TREATMENT

Start scouting:First unolded lea (Stage 7).

Favourable conditions:Warm temperature (20 - 27 C)and relative humidity isat 60 % or above.

Critical period:

From 4 - 6 unorded leaves (stage

12) to veraison (stage 35).

Susceptible cultivars:Ater the rst primary inection (symptoms havebeen detected) or beginning o fowering.

Moderately susceptible cultivar:Ater the rst primary inection (symptoms havebeen detected) or 50 % fowering.

OTHER SPRAYS

Frequent scouting is required.

Susceptibility is highest romfowering to veraison.

Risk o powdery mildew increases

with increasing temperature(20 - 27 C) and humidity

Powdery mildew lesions are presentin the vineyard.

Consider vine growth rate, mode o actionand persistence o ungicide, and conditionswhile spraying.

END OF SPRAYS

Monitor the presence andincidence o sporulating lesionsin the vineyard.

Older leaves are less susceptible;The risk o inection endsat veraison.

Avoid high levels o lea (or berry)inection at the end o the seasonin order to minimize primaryinoculum the next season.

Beginning o veraison in healthy vineyard(absence o symptoms).

Mid-veraison i the disease is present.


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2727

Powdery mildew management based on disease risk estimations

Grape powdery mildew is awind-disseminated disease. Inother words, spores producedon lesions are dispersed bywind. Airborne spores all onleaves and cause new le-sions which in turn producenew spores that are wind-disseminased and so on.

Studies, conducted in Quebec, showed that the amount o sporesin the air, hence increasing the risk o powdery mildew inectionis infuenced by the accumulation o heat units. A degree-day

model was been developed to determine the best time to initiatea spray program. By using this model, it is possible to eliminateearly ungicide sprays when the risk o inection is low and tospray when the risk is high. Degree day values are calculateddaily rom hourly temperatures using 6 C as the base temper-ature but excluding hours with temperature above 30 C. Degreedays are accumulated rom the green tip growth stage.

When heat units are at less than there is a low risk oinection: it is advised to scout or the presence o powderymildew symptoms. I lesions are detected then startungicide sprays.

When heat units are between 500 and 600 there is anincrease risk o inection; it is advised to scout more otenand to initiate the spray program on susceptible cultivars.

When the risk o inection reaches the action thresholdi.e heat units are anywhere between 600 and 700, itis advised to scout more oten and to initiate the sprayprogram or cultivars that are moderately susceptible.

0 200 400 600 800 1000 1200 1400 1600 1800

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Risk is moderate

If the disease is present,

initiate the fungicide

spray program.

Degree-days accumulated since growth stage 5

Pro

portionofseasonnalinoculum

Predicted

Lower limit

Upper limit

Risk is low Risk is high

Initiate the fungicide

spray program.


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2828

Bunch rot, grey mold Botrytis cinerea

Gray mold or Botrytis bunch rot sporadically causes sub-

stantial yield reductions in Quebec vineyards. The causal

agent Botrytis cinerea, can cause ruit rot in several plants,

among which strawberries and raspberries. The disease

can progress rapidly during berry ripening and cause sig-

nifcant yield losses. The disease can be difcult to control

because o the development o resistance to some ungi-

cides in B. cinereapopulations.

Symptoms

B. cinereais present in all ruit producing areas, including mostvineyards. Symptoms are generally more obvious on berries,however buds and young shoots can also show signs o inec-tion and turn brown. In late spring, V-shaped or irregular brownpatches may appear on leaves. Inected inforescences may beblighted and dry up.

Some fower inections can remain latent (invisible) until veraison.Fruits become more susceptible as they begin to ripen (veraison);B. cinereainect berries by penetrating directly through the sur-ace o the skin or through wounds, and may continue to invadeuntil the entire cluster is covered with gray spores.


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B

CA

C

2929

Bunch rot disease cycle

Winter Botrytis cinerea overwinters as sclerotia (masses ocompact mycelium) in crop debris. Sclerotia are oten ound inmummied berries on the ground at the end o the season. (A)

Spring Sclerotia produce spores (conidia) that are spreadthroughout the vineyard by wind and rain. Spores that are de-posited onto leaves and fowers are responsible or causingprimary inections. (B)

Summer On fowers, conidia cause latent inections that are

visible only later in the season ater veraison. These conidia

germinate when relative humidity is high (> 90 %) or under wet

suraces, provided that the temperature is between 1 and 30 C

(optimum at 18 C) . Inected berries turn brown and purple

During dry weather conditions, inected berries dry out; in wet

weather, they tend to burst and become covered with a grayish

mold. (C)

Inection is more severe on tight clustered varieties or clustersaected either by powdery mildew, hail or insect damage (ex-ample: grape berry moth).

Fall Sclerotia are mainly ormed in mummied berries thathave allen on the ground.


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3030

Bunch rot management

Susceptibility Leaves are more susceptible when they are

senescent or damaged. Inforescences are susceptible during

the entire fowering period. Berry susceptibility increases as their

sugar content increases.

Critical period From the beginning o fowering (stage 19 - 21) to

berry touch (stage 33) and throughout berry ripening until harvest.

Inections Inection severity depends on actors such as tem-

perature, duration o lea or berry wetness or high relative humidity

(> 90 %) (see table below) and cultivar cluster type. Closely monitor

cultivars that are tight clustered (Vidaland Seyval).

MEAN AIR

TEMPERATURE

(C)

WET PERIOD DURATION

REQUIRED FOR INFECTION

(HOURS)

10 30

15.5 18

22.5 15

26.5 22

39 35

Preventive measures Avoid excessive growth by ertilizingappropriately. Use pruning and canopy management practicesthat avour air circulation and rapid drying o leaves and berriesI there is history o disease, remove leaves around the clustersor susceptible cultivars to promote air circulation. Control weedsto reduce humidity in the lower portion o the canopy. Try asmuch as possible to minimize berry damage caused by birdsmachinery or insects and destroy pruning debris.

Management strategy For elds that have a history o bunchrot or i highly avourable weather conditions are present thenapply ungicide during these our growth stages: bloom, berrytouch, veraison and beore harvest.

Note: Some adjuvants added to ungicide mixes may damage thewax on berries which serve as a natural barrier to inections byB. cinerea.


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3131

Bunch rot management in brie



Start scouting:Stage 19-21 and 35 to harvest.

Favourable conditions:Warm temperature and highrelative humidity.

Critical period:

Beginning o fowering

(stage 19-21) to berry touch

(stage 33) and during berry

ripening until harvest.

Susceptible cultivars (tight cluster):Protect fowers against latent inection at 80 %fowering (Stage 25) and at berry touch.

OTHER SPRAYS

Pay attention to weather conditionsduring fowering. Risk o inectionincreases with rainall requency,warm temperatures and duringperiods o high relative humidity.

Scout or inected inforescences.

Beore berry touch on very susceptible cultivars.

END OF SPRAYS

While scouting takes down the% o inected clusters.

As sugar levels increase during

berry ripening, so does theirsusceptibility to bunch rot.

At the end o the season, avoidlarge amount o mummied berriesto reduce primary inoculum thenext season.

Beore harvest i symptoms are present.

Check with an nologist or the eect o lateungicide applications on wine quality.

Respect pre-harvest delay recommended by themanuacturers (see labels).


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3232

Anthracnose Elsinoe ampelina

Anthracnose is a ungal disease that originated rom Europe.

Vitis viniera species are generally susceptible to the dis-ease whereas wild species are generally less susceptible.

Mild inections by E. ampelinaare enough to reduce vigour

and yield when compared to healthy vines. Severe inec-

tions reduce shoot growth, quality and quantity o ruits, and

winter-hardiness.

Symptoms

E. ampelinaattacks all above-ground parts o the vine. Lea symp-

toms appear as small circular black or brown spots. As the lesions

mature, the center drops out, creating a shot-hole appearance.

On the petioles and shoots, E. ampelinacauses deep, elongatedcankers, with a grayish centre and black edges. In some cases,

the lesions will be so deep that the shoot breaks, causing total

loss o production on that shoot. During severe inections, the

leaves shrivel up and all. Inected berries also develop sunken

spots with a grayish centre and black edges. Severely inected

berries dry up and drop prematurely.


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B

AA

C

3333

Anthracnose disease cycle

Winter The complete lie cycle o E. ampelina is not known.However, the ungus likely overwinters as sclerotia (compactmass o mycelium) produced in mummied berries and in can-kers o young canes in late summer or all, when the host tissuelignies. (A)

Spring Sclerotia produce spores that are released when tem-peratures are above 2 C and ater a rainall o at least 2 mm.These spores will inect opening buds, leaves, wood and ruit,causing primary inections. (B)

Summer Secondary inections are caused by spores producedon inected tissues early in the season (young shoots, tendrilspetioles, leaves and inforescences), these spores spread bysplashing rain. Symptoms appear 3 to 7 days ater inection hasoccurred. (C)

Fall Sclerotia are produced in mummied berries and in canecankers. The sclerotia can remain viable or 3 to 5 years. (A)


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3434

Anthracnose management

Susceptibility Young developing leaves and shoots along withInforescences are highly susceptible to anthracnose. Berries aresusceptible to inection rom initiation to veraison.

Critical period From the rst unolded lea (stage 7) to verai-son (stade 35).

Inections Temperature does not appear to be a limiting actorbecause inection can take place at temperatures ranging rom 2to 40 C. However, the duration o wetness may limit inections.The minimum duration o wetness needed to cause an inectionwill vary with temperature.

MEAN AIR

TEMPERATURE

(C)

WET PERIOD DURATION

REQUIRED FOR INFECTION

(HOURS)

12 7 - 10

16.5 4 - 7

21 3 - 4

30 1.5

Preventive measures Anthracnose management is requiredonly on susceptible cultivars such as Vandal-Cliche and duringrainy seasons on moderately susceptible cultivars such as Prai-rie Star. Anthracnose must be managed i it was present duringthe last 2-3 seasons.

Sclerotia responsible or primary inections in the spring over-winter in inected pruning debris; thereore it is important toremove them rom the vineyard ater pruning to reduce inoculumor next year. Avoid excessive growth by proper ertilization andkeep weed populations under control.

Management strategy I anthracnose was present the previ-

ous season, primary inections could be limited by an applica-tion o Lime-sulphur at budbreak. The strategy or anthracnosemanagement is based on a good control o lea inections early inthe season to avoid berry inections and cane cankers ormationas much as possible. Stem cankers reduce vine vigor and theyare sources o inoculum or subsequent inections throughoutthe season.


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3535

Anthracnose management in brie



Start scouting:Stage 7.

Favourable conditions:Frequent rainall.

Critical period:

Stage (7) rst unolded lea

to veraison.

Anthracnose was present last season:

Apply a lime-sulphur based productat budbreak.

Susceptible cultivars: preventive ungicidesprays starting with new growth

Moderately susceptible cultivars:When lesions are detected in the vineyard

I rain is orecasted, spray beore.

OTHER SPRAYS

Susceptibility remains throughoutthe season.

The more requent the rainall,the greater the risk o inection.

Symptoms are present.

Consider vine growth rate, mode o actionand persistence o ungicide, and conditionsduring spraying.

END OF SPRAYS

Scout or the presence o symptoms(mummied ruits and cane cankers).

Older leaves are less susceptible but

berries are at risk until harvest

At the end o the season, remove canecankers to reduce inoculum or thenext season.

Susceptible cultivars:At harvest.

Check with an nologist or the eect o

late ungicide applications on wine quality.

Respect the pre-harvest intervalrecommended by the manuacturers(see labels).

Moderately susceptible cultivars:Veraison i disease was not detected.


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3636

Black rot Guignardia bidwellii

Black rot is a ungal disease native to North America caused

by a pathogen called Guignardia bidwellii. The disease is

generally more severe during wet spring weather conditions

and periods o rapid vine growth. Black rot can inect ber-

ries and all new green tissues o the vine (leaves, petioles,

shoots, and tendrils).

Symptoms

On the leaves, G. bidwelliiinduce more or less circular spots o2 to 10 mm in diameter, these lesions start appearing one to twoweeks ater inection has occurred. Lesions are light brown atrst, than turn reddish with a ring o small black ruiting bodies(ungal sporulation), visible to the naked eye. Lesions are sur-rounded by a dark brown coloration. Cluster stem and pedicel,lesions are small and sunken. Black cankers may develop onstems.

The rst symptoms on berries are small whitish dots surroundedby a reddish-brown halo, later inected berries become milkyand within a ew days, the berries start to shrivel and turn intohard, blue-black commonly called mummies. Berries become re-sistant to inection about 3 to 5 weeks ater bloom. I berries areinected when resistance is established, lesions remain localized.


37/47

B

CA

C

3737

Black rot disease cycle

Winter The ungus overwinters as perithecia (ruiting bodycontaining spores) on ruit mummies that remain inside the can-opy or on the ground. (A)

Spring Spores (ascospores) are produced within peritheciaand are dispersed by wind and rain. Perithecia start releasingspores shortly ater bud break until about 2 weeks ater bloom.These spores cause the primary inections. (B)

Summer About 2 to 3 weeks ater primary inections have oc-cured, brown lesions with small ungal ruiting bodies (pycnidia)will appear. New spores (conidia) will be produced in these ruitingbodies and splashing rain will spread conidia onto leaves, stem,

tendrils, inforescences and berries causing secondary inections.

Under avourable conditions, it is possible that primary (causedby ascospores) and secondary inections (caused by conidia)overlap.

New spores will be produced ollowing secondary inections andcause new inections. Under optimal temperatures o 20-25 Cnew lesions will appear in 5 to 7 days. (C)

Fall At the end o the season, ruit mummies all on the groundPerithecia are produced in ruit mummies. (C)


38/47


39/47

3939

Black rot management in brie



Start o scouting: Stage 5.

Favourable conditions:Temperature o 9 C or above with wetperiods lasting or at least 6 hours.

Critical period: budbreak (stage 5)

to veraison (stage 35).

Susceptible cultivars:Initiate the spray program i black rotwas present last season and rainsare orecasted.

Moderately susceptible cultivars:Ater the rst primary inections(symptoms are detected).

Spray beore major rain.

OTHER SPRAYS

Berries are susceptible until about3 - 5 weeks ater bloom (berry touch).

Risks increase with increasingtemperatures rom 9 to 32 C and withduration o wet periods.

Symptoms are present in the vineyard.

Consider vine growth rate, mode o actionand persistence o ungicide, and conditionsduring spraying.

END OF SPRAYS

Scout or the presence o inoculum (brownlesions with black spots).

Berries are resistant ater berry touch

(stage 33).

At the end o the season, avoid largeamount o ruit mummies to reduceprimary inoculum the next season.

Beginning o veraison in healthy vineyard(no new symptoms o black rot).

Mid-veraison i symptoms were present

but disease under control.


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4040

Crown gall Agrobacterium vitis

Crown gall is caused by the bacterium Agrobacterium vitis,

the pathogen is present in several vineyards and can be

a serious problem because it is dicult to control. The

bacterium is most probably disseminated in grapevine

propagative material, and unortunately there is no

certication program to ensure that nursery stock has been

tested and is ree o bacteria.

Symptoms

In general, crown gall is most severe in areas where winterinjuries are common. Vitis labruscacultivars are less susceptiblethan hybrids or V. vinifera.

Crown gall reduces vine growth, longevity, and yield o inected

plants will depend on the severity o galling. Galls may girdle the

trunk preventing the fow o nutrients to the vine. Inected vines are

stressed and are more prone to winter damage.

In some cases, galls may aect only a portion o the trunk (cambium)

and the vine will continue to produce berries. However, once a vine

is inected, production o new galls will continue during subsequent

years which will reduce vine growth. The bacterium responsible

or crown gall survives in the soil and hence disseminated by

machinery. In general, crown gall is most severe in

areas where winter injuries are common.


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4141

Crown gall disease cycle

The causal agent,Agrobacterium vitis, is an opportunistic patho-gen that attacks damaged cells. The bacteria can survive in thevascular system o the vine or many years without showing anysymptoms until some cell damage occurs. The bacterium theninvades plant cells associated with the plants natural wound-healing process.

In early summer new galls are smooth and light brown, with agethey hardened, turn dark brown, brittle and corky. In general,galls are seen on the lower parts o the vines near the ground.

The bacteria can survive in the vascular system

o the vine or many years without showing anysymptoms until some cell damage occurs.


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4242

Preventive measures or crown gall

Development o crown gall is associated with winter injury and

damage caused by machinery; hence, any cultural practice aimingat reducing winter injury will help manage the disease. Heavilydiseased plants must be removed and replace with plants reeo bacteria. Covering the lower part o the vine with soil will helpprotect new shoots rom winter damage and help with trunkrenewal. Begin monitoring or crown gall in lowers parts o thevineyard and in areas with poor drainage.

It is important to removed diseased plants because the bacteriumcan remain in decaying root pieces in the soil or several yearsand serve as a source o inoculum or new inections. When avine is removed, make sure that all roots have been removed as

well to avoid contamination o new vines.

Crown gall management strategy

Since the bacteria survive in the vascular system o the inectedvines, hot water treatment o vines beore planting is an eect-ive control measure. Since hot water treatments kill most butprobably not all o the bacteria, it is not guaranteed that planting

stock will be completely disease-ree. Sensitivity to hot watertreatment varies with cultivar. Sensitivity o cuttings to hot watertreatments depend on when cuttings were treated during thedormant season.

Covering the lower part o the vine with

soil will help protect new shoots rom winterdamage and help with trunk renewal.

Hot water treatment o vines beore

planting is an eective control measure.


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4343

Acknowledgements

Reviewers

Martine Cot, Agronomist, Direction rgionale de la Capitale Nationale, Quebec Ministry of Agriculture, Fisheries and Food Richard Lauzier, Agronomist, Quebec Ministry of Agriculture, Fisheries and Food

Ginette Laplante, Technologist, Quebec Ministry of Agriculture, Fisheries and Food

velyne Bariault, Agronomist, wine concellor, Duraclub inc.

Dominique Choquette,Agronomist, Club agroenvironnemental de lEstrie

Danya Brisson, Agronomist, Quebec Ministry of Agriculture, Fisheries and Food

Isabelle Turcotte, Agronomist, wine concellor

Collaborators

Socit de Dveloppement conomique des Rgions (SDER)

Vignoble de lOrpailleur

Vignoble La Bauge

Vignoble Dietrich-Jooss

Funding

Agriculture and Agri-Food Canada(AAFC):Pest Management Centreand Horticulture Research and Development Centre


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Phenological stages

1. Winter dormancy

2. Bud swelling

3. Wool (doeskin stage)

5. Bud burst

6. Green shoot

7. First lea unolded

9. 2 to 3 leaves unolded

12. 4 to 6 leaves unolded,inforescence clearly visible

15. Inforescence elongating;fowers closely pressed together

17. Inforescence ully developed;fowers separating

19. Beginning o fowering;rst caps alling

21. Early fowering;25 % o caps allen

22. Full fowering;50 % o caps allen

25. Late fowering;80 % o caps allen

27.Young ruits beginning to swell

29. Berries small; bunches beginto hang (4 - 6 mm)

31. Berries pea-sized;bunches hang (7 - 10 mm)

33. Beginning o berry touch

35. Beginning o berry ripening

(veraison)38. Berries ripe or harvest

Illustration adapted rom Eichhorn and Lorenz (1977) and Lorenz (1994).Please see photos on next pages.


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Stage 3 Wool (doeskin stage)Stage 1 Winter dormancy Stage 5 Bud burst

Phenological stages: photos

Stage 15 Inforescence elongating; fowersclosely pressed together

Stage 17 Inforescence ully developed;fowers separating

Stage 12 4 to 6 leaves unolded, inforescenceclearly visible

Stage 23 Full fowering; 50% o caps allen Stage 25 Late fowering; 80% o caps allenStage 19-21 Beginning o fowering; rst capsalling - Early fowering; 25% o caps allen

Stage 7 First lea unoldedStage 6 Green shoot Stage 9 2 to 3 leaves unolded


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Stage 29 Berries small; bunches beginto hang (4 - 6 mm)

Stage 31 Berries pea-sized;bunches hang (7 - 10 mm)

Stage 38 Berries ripe or harvest

Stage 33 Beginning o berry touch

Stage 27 Fruit set; young ruitsbeginning to swell

Stage 35 Beginning o berry ripening; i it applies, beginning o loss o green color (veraison)

Phenological stages : photos (contd)


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Documents

Grape Diseases Menagment in Canada