Diseases of Greenhouse Cucumbers and Tomatoes

Sustainable Management ofVegetable DiseasesKLAS Winter Lecture SeriesTarry’s Hall, Castlegar, , BCMarch 20, 2010Ron Howard, Ph.D., P.Ag.Alberta Agriculture and Rural DevelopmentCrop Diversification Centre South, Brooks, AB

Outline• To Begin - Some Definitions• Factors Favoring Disease Development• Economic Importance of Vegetable Diseases• Basic Disease Scouting Techniques• Tips for Diagnosing Vegetable Diseases• Developing a Sustainable Disease ManagementProgram for Vegetable Crops• Questions• Short Break

What is a Plant Disease?• Disease is a departure from normal health in aplant that is usually recognized by the presenceof symptoms or signs• Symptoms are the internal or external reactionsor alterations of a plant that occur as the resultof a disease• Signs are the evidence of a pathogen ordisease-causing agent on or in the plant

Major Types of Plant Diseases• Non-infectious Diseases – Caused byenvironmental stresses such as extremetemperatures, excesses or deficiencies ofnutrients or water, low light, pesticidemisapplication, mechanical injury, etc.• Infectious Diseases – Caused by plant pathogenicbacteria, fungi, viruses, phytoplasmas,nematodes, etc.

Disease Development• Most of our common infectious and non-infectiouscrop diseases occur year-in and year-out and theyare often found together in the same field• Levels of infectious diseases depend upon theinteraction between the Host Plant, theEnvironment and a Pathogen(“The Disease Triangle”)• Non-infectious diseases depend upon theinteraction between the Host Plant and theEnvironment

The Disease TrianglePathogenEnvironmentDISEASEHost

Weather Effects• The weather is the single most important factoraffecting the development and spread of infectiousplant diseases• It also has a major influence on the occurrence ofnon-infectious diseases• Bacterial and fungal diseases usually have theirgreatest impact when warm/wet or cool/wetconditions prevail versus when warm/dry orcool/dry conditions exist

Clubroot Disease CycleOhio StateUniversity

Economic Importance of Plant Diseases• Annual crop disease losses in North Americaare estimated to average 11.3%• All crops are affected by diseases• Both yield and quality can be reduced• Losses can be additive when you include thecosts of management strategies, especially“rescue treatments”• Effective disease management programs candetermine whether a farm succeeds or fails

Basic Disease Scouting Techniques• Scouting allows you to identify diseases early in thegrowing season when it may still be possible toslow down or stop their spread• It helps you determine where a disease is in thefield and how fast it may be spreading• It may help you to determine the effectiveness ofcertain control practices• Scouting could help to reduce yield and qualitylosses and therefore save you time and money

Preparing for Disease Scouting• Review publications or online databases that tellyou what diseases can occur on the crops you’regrowing and especially in your area• Acquire some diagnostic aids, e.g. crop protectionguides, pictures of symptoms and signs,descriptions of disease cycles, test kits, etc.• Develop a scouting plan that matches the crop,diseases present, and production system in use• Prepare a scouting kit to take to the field

Components of a Scouting Kit• Hand lens (5X, 10X, 15X)• Flashlight and camera• Pocket knife, utility knife or pruning shears• Plastic bags, ties, vials and labels• Hand trowel or small shovel• Pens, pencils, paper and envelopes• Tweezers, needles and paper towels• Rubber boots/boot covers and disinfectant• Reference materials• Plastic tool box

The Process of Crop Scouting• Crops should be scouted at least weekly betweenemergence and maturity• Crops may have to be scouted more intensively atcertain times because of local outbreaks,vulnerability of specific growth stages, unusualweather conditions, etc.• Keep careful records (written and pictures) ateach inspection• Mark “hotspots” or questionable areas to return tolater

The Process of Crop Scouting• Walk a “W”, zigzag or row pattern through the field,stopping every 50-100 steps to closely examine theplants at that spot• Use flags to mark specific areas for regularmonitoring throughout the growing season• Be most diligent when scouting “high risk” fields orcrops• Check areas that are potential hot spots for diseasedevelopment• Carefully inspect the entire plant

Collecting Plant Samples• Choose plants showing various stages of diseasedevelopment and some healthy ones forcomparison (more is better!)• Collect the whole plant, where possible, takingcare to dig rather than pull up the roots• Note the types of symptoms present and thedistribution of affected plants within the field• Take pictures (digital format preferred)• Collect information on field conditions and thecropping history

Collecting Plant Samples• If plants are going to be submitted to a lab orstored for a few days, you should:- Dig plants, transfer them to containers andwater them occasionally- Wrap specimens in a dry or lightly moistened(not wet!) paper towel- Wrap root balls in a plastic bag and tie off at thesoil line to avoid contamination of foliage- Pack samples well in a rigid container with coldpacks if they are going to be shipped out to a labor specialist

Tips for Diagnosing Plant Diseases• Diagnosis is the process of determining thecause or causes of a disease through closeexamination and analysis• An accurate diagnosis is usually neededbefore effective control measures can betaken for the current crop and/or before apreventative program can be planned for thenext crop• Diagnostic skills improve with experience• Don’t be afraid to seek professional help, e.g.plant health labs, specialists and consultants

Characteristics of Healthy Plants• Vigorous root and stem growth• Well-developed foliage, fruit, tubers or roots• Uniform color• Presence of new growth• Abundant, evenly distributed flowers• Healthy, well-branched, evenly distributedroots• Even growth across the crop

Characteristics of Diseased Plants• Weak or uneven growth• Fewer leaves and flowers• Absence of new growth• Poor or non-uniform coloration• Reduced height, stunting or malformations• Lesions, cankers, galls, rot, etc.• Wilting or death• Signs of pathogens

Diagnostic Assistance and InformationB.C. Ministry of Agriculture and Lands:Plant Diagnostic LaboratoryAbbotsford Agriculture Centre1767 Angus Campbell RoadAbbotsford, BC V3G 2M3Tel: 604 556-3126 or 1-800-661-9903Fax: 604 556-3154Crop Consultants and Diagnosticians:‣ Elmhirst Diagnostics and ResearchAbbotsford, BC; Tel: 604-820-4075‣ CropHealth Advising & ResearchKelowna, BC; Tel: 250 - 717-1898

Diagnosing Plant Diseases• Develop a collection of resource information onthe prevalent diseases affecting the crops you’reresponsible for• Bookmark key websites for commodityorganizations, government and educationalinstitutions, and agronomy publications- www. agf.gov.bc.ca- www.al.gov.bc.ca/pesticides/- www.omafra.gov.on.ca- www.plant-disease.ippc.orst.edu/links.cfm

Canadian Phytopathological Societyhttp://www.cps-scp.ca/

American Phytopathological Societyhttp://www.apspress.com

www.gov.on.ca/omfra/www.agf.gov.bc.ca

http://www.agf.gov.bc.ca

Organic Friends' E-Zine/Cyberbulletin Les amis du bioMarch 2010 marsContact Information / Contactez-nousJoanna MacKenzie, M.Sc.Website Co-ordinator / Coordonnatrice du site Webjmackenzie@nsac.caPh: 902-896-2469

[=========================================IPMnet NEWSIssue #177 March 2010[=========================================Global Principles, Local PracticesProviding global Integrated Pest Management informationTHIS ISSUE:--------------------------------------I. News about IPM- IPM and Australian Vegetable Production- IPM Grants Emphasize Education and Extension> Global IPM Notes--------------------------------------II. IPM Information Resources> Other Recently Published Items--------------------------------------III. IPM Medley- Conjuring Up Unearthly Weeds> Equipment, Products, Processes, & Services> Professional OpportunitiesIPMnet@science.oregonstate.edu

Cornell UniversityIthaca, NYhttp://nysipm.cornell.edu/organic_guide/cole_crops.pdfProduction Guides for:• Beans• Carrots• Cole Crops• Cucurbits• Lettuce• Peas• Potatoes• Spinach

Diagnostic Test Kits• Agdia Inc. (www.agdia.com)• Neogen Ltd. (www.neogen.com)• Bioreba AG (www.bioreba.ch)• Hydros Inc. (www.hydros.cc)• Forsite Diagnostics (www.pocketdiagnostic.com)

Developing a Sustainable DiseaseManagement ProgramImportance of Disease Management• Diseases can reduce the quantity andquality of plants and their products• Plant diseases can cause direct financiallosses to producers and processors• The cost of controlling plant diseases canbe high and, in some cases, prohibitive• Disease management can mean thedifference between success and failure ina farming business

Developing a Sustainable DiseaseManagement ProgramKey Criteria• Know the optimal growing conditions for thecrops you’re producing and what a healthy cropshould look like• Learn to recognize the major infectious andnon-infectious diseases that may affect thecrops you’re growing• Develop a disease management program that iseffective, affordable, practical andenvironmentally sustainable over time• Emphasize preventative practices!

Developing a Management Programfor Non-Infectious Diseases• Preventing situations that may predisposeplants to non-infectious diseases by providingoptimal conditions for plant growth• Remedying problems that develop may requiresudden or gradual changes in growingpractices, e.g. altering fertilizer programs,irrigation schedules, seeding rates, rowspacings, tillage practices, etc.

Developing a Management Programfor Infectious DiseasesFour strategies form the basis of managementprograms for infectious plant diseases:• Eradication – Eliminating or reducing pathogeninoculum from the field• Exclusion – Keeping pathogens away fromplants to help them escape infection• Protection – Preventing or limiting infection anddisease spread within crops• Host Resistance - Planting disease-resistant ortolerant crop varieties that are less likely tosuccumb to infection

Eradicating Pathogen Inoculum• Destroying infected crop residues throughtillage and crop rotations• Sanitizing buildings and equipment• Treating water, nutrient solutions and growingmedia• Eliminating secondary hosts, e.g. weeds andvolunteer plants• Using biological and chemical pesticides - Checkpesticide registrations on the Pest ManagementRegulatory Agency website (http://pr-rp.pmraarla.gc.ca)

Excluding Pathogens from Crops• Separating or segregating new, healthy cropsfrom old, infected crops• Manipulating the environment to help preventinfection, e.g. reducing relative humidity byirrigation scheduling• Using disease-free seed• Applying protectant or eradicant fungicides tothe seed, foliage or roots

Protecting Crops from Infection• Limiting inoculum production by controllingenvironmental conditions• Limiting inoculum dispersal, e.g. by cleaningequipment between fields• Controlling pathogen vectors, e.g withpesticides, predators and physical traps• Limiting pathogen survival, e.g. by usingdisinfectants and pesticides

Planting Resistant Varieties• Genetic resistance is the first line of controlfor most plant diseases and is preferred overall other means• This strategy may be unavailable for somekinds of plant diseases• Improving growing conditions for plants mayenhance vigor and natural resistance topathogens and environmental stresses

Integrated Disease Management• Using as many disease management practicesas possible at one time, e.g.:- Providing optimal growing conditions- Eliminating pathogens- Avoiding infection- Limiting disease spread- Planting resistant varieties- Using biological and chemical controls

Characteristics of a Non-sustainableDisease Management Program• It is reactive rather than preventative• It is ineffective, e.g. fungicide sprays areapplied too late to protect plants• It is uneconomical, e.g. input costs cannot beoffset by financial returns• It is impractical, e.g. the crop is too badlyaffected and cannot be saved• It is unsustainable, e.g. it cannot becontinued over time

Contact InformationRon Howard, Ph.D., P.Ag.Plant Pathology Research ScientistAlberta Agriculture and Rural DevelopmentCrop Diversification Centre South301 Horticultural Station Road EastBrooks, Alberta T1R 1E6Email: ron.howard@gov.ab.ca