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Plant Health (Horticulture III)

Course CodeBHT116
Fee CodeS2
Duration (approx)100 hours
QualificationStatement of Attainment

PLANT HEALTH: Learn to identify Plant Pest and Disease Problems and how to Manage Them

Government, nursery and private positions are more demanding then they ever were; employers are becoming increasingly selective choosing personnel with broad horticultural knowledge and less emphasis is placed on the 'learn on the job' approach of years gone by. Education is imperative if you expect to compete in this field and those that have the knowledge will also have the best chance of reaping the rewards.

  • Learn to identify plant pest and disease problems
  • Learn to evaluate a sick plant, and determine nutritional and environmental issues
  • Study pest and disease control and managing plant health
  • Expand your horticultural skills for improved career success in horticulture

A sick plant may be sick due to one cause, but often it is due to several causes at the same time. There are thousands of possible causes which can contribute to a plant's problems. Minor diseases or environmental problems may weaken the plant, making it susceptible to some more major (obvious) disorder. When you inspect a plant for problems, you should systematically consider all of the things which might possibly be going wrong. This course provides the foundation for inspecting diagnosing and treating all types of problems.

This subject develops a firm understanding of plant health, the systematic identification of health problems

Lesson Structure

There are 10 lessons in this course:

  1. Introduction
    • Pests
    • Diseases
    • Common terminology
    • Diagnosing problems systematically
    • Tell tale symptoms
    • Conducting an inspection: four steps
    • Pest or disease reviews
  2. Overview of Preventative Controls
    • Introduction
    • Methods of pest management
    • Integrated pest management
    • Cultural control
    • Using disease resistant varieties
    • Crop rotation
    • Timed planting
    • Mulching
    • Cleanliness
    • Biological control
    • Types of biological controls
    • Beneficial plants
    • Trap or decoy plants
    • Pheromone traps
    • Physical controls
    • Traps
    • REpellants
    • Mulching
    • Pruning
    • Wounds
    • Chemical controls
    • Understanding pesticides
    • Safely storing chemicals
    • Safely mixing chemicals
    • Legalities
    • Plant breeding for resistance
    • Sources and causes of resistance
    • Adaptability, resistance and pest variability
  3. Insecticides
    • Types of insecticides: systemich, stomach poisons, contact poisons, etc
    • Inorganics, botanicals, organophosphates, carbamates, synthetic pyrethroids
    • Characteristics of insecticides: toxicity, spectrum, LD50, persistence, volatility, etc.
    • Golden rules for handling pesticides
    • Terminology
  4. Other Pesticides
    • Chemical Pesticides: introduction
    • Review of common pesticides
    • Soil treatment for control of diseases
    • Soil pests
    • Types of fumigtants
    • Systemic fungicides
    • Comparative toxicities
  5. Spray Equipment
    • Types of sprayers
    • Uses of sprayers
    • Spray terminology
    • Sprayer maintenance and cleaning
    • Selecting a sprayer
    • Calibration
    • Using chemicals: agitation, clean up and disposal
    • Basic first aid with chemical pesticides
    • Response to liquid or powder spills
    • Keeping records
    • Misters, Dusters, Blowers
    • Pesticides and the environment
  6. Insect Biology
    • Insect classification: orders, sub classes
    • Insect anatomy: mouthparts, legs, etc
    • Lifecycle
    • Feeding habits
    • Practical project: Insect collecting, preserving, identifying, for an insect collection
    • Common insects that a gardener encounters
    • Ants
    • Aphis
    • Beetles
    • Borers
    • Bugs
    • Caterpillars
    • Cockroaches
    • Crickets
    • Earwigs
    • Fleas
    • Flies
    • Galls (caused by insects)
    • Grasshoppers
    • Ladybirds (good and bad)
    • Leaf hoppers
    • Leaf miners
    • Lerps
    • Mealy bug
    • Mosquitos
    • Scale insects
    • Termites
    • Thrips
    • Wasps
    • Whitefly
  7. Fungal Biology
    • What causes disease
    • Symptoms of disease
    • Lifecycle of a disease: inoculation, penetration, infection, growth and reproduction, dissemination
    • Fungi groups: obligate saprophytes, obligate parasites, facultative saprophytes, facultative parasites
    • Expanded concept of tree decay
    • Chemical pesticides in the UK and Europe
    • Common diseases
    • Anthracnose
    • Bitter pit
    • Blights
    • Botrytis
    • Canker
    • Cinnamon fungus
    • Club root
    • Damping off
    • Galls
    • Gummosis
    • Leaf curl
    • Leaf spot
    • Melanose
    • Mildews
    • Rots
    • Rust
    • Scab
    • Silver leaf
    • Spot
    • Smut
    • Sooty mould
    • Wilts
  8. Environmental Problems
    • Common environmental problems
    • Foliage burns
    • Pollution
    • Lack of water
    • Drainage problems
    • Frost
    • Hail
    • Shade
    • Temperature
    • Wind
    • Symptoms of nutritional deficiencies
    • Air pollution
    • The plant and water
    • Non parasitic problems in turf (lawns)
    • Ways to provide environmental protection to plants
  9. Viruses
    • Overview
    • Symptoms
    • Detection and diagnosis of viruses
    • Control
    • Examples of virus diseases
  10. Nematodes, Molluscs and Crustaceans
    • Overview
    • Millipedes
    • Plant nematodes
    • Nematodes in citrus
    • Red spider mites
    • Spiders
    • Slaters or wood lice
    • Snails and slugs

Each lesson culminates in an assignment which is submitted to the school, marked by the school's tutors and returned to you with any relevant suggestions, comments, and if necessary, extra reading.


  • Identify the characteristics of pests and diseases of plants.
  • Explain methods for the control of pests and diseases.
  • Describe the characteristics of a range of different pesticides, including insecticides
    • and fungicides.
  • Explain the selection and use of spray equipment appropriate for different
    • specified tasks.
  • Describe aspects of the biology of an insect which are relevant to pest control.
  • Describe aspects of the biology of an fungus which are relevant to disease control.
  • Explain how inappropriate environmental conditions can affect plant health.
  • Identify the characteristic signs of a range of non-insect pests,
    • and select apropriate control methods.

What will You Actually Do in this Course? -all of the following, and more....

Develop a checklist for determining the significance of pests and diseases, which addresses different criteria including:

  • short term impact
  • long term impact
  • economic impact
  • aesthetic impact.

Distinguish between the main types of plant diseases, including:

  • fungal
  • viral
  • bacterial.

Create a standard worksheet for reviewing pest and disease problems of plants.

Diagnose different problems (ie. pests or diseases), documenting the problem on a standard pest/disease review worksheet.

Describe different ways to control pests and diseases, including:

  • Application of chemicals
  • Plant selection
  • Companion planting
  • Cultural techniques (i.e. improving ventilation, improving drainage)
  • Physical control (i.e. pruning, hand removal, trapping, hosing off).

Explain how plant breeding has been used to improve pest/disease resistance in different plant species.

Explain three biological control methods for dealing with specific problems.

Develop an IPM strategy for a specific situation such as a crop or garden, considering:

application procedures, remedial action and monitoring.

Describe plant hygiene practices for a specific situation such as a crop, nursery or garden, in line with industry practice, enterprise guidelines and sound management practice.

Recommend control methods for different pest and/or disease problems diagnosed.

List safety procedures to follow when handling pesticides.

Distinguish between the main groups of pesticides, including:

  • organo-phosphates
  • synthetic pyrethroids
  • carbamates
  • chlorinated hydrocarbons.

Explain the difference between the action of systemic and non-systemic pesticides.

Explain maintenance practices, including cleaning, for a specified sprayer.

List different uses for several types of sprayers, including a motorised pump sprayer, a knapsack and a PTO driven tractor mounted sprayer.

Compare different sprayers, in terms of:

  • cost
  • applications
  • maintenance
  • spare parts
  • ease of use
  • safety.

Explain the application of chemicals in a given situation, including:

  • Calibration
  • Mixing chemicals
  • Equipment operation
  • Safety measures
  • Post spray procedures such as cleaning, and storage of chemicals).

Describe the minimum records which should be kept when spraying pesticides.

Prepare a labelled diagram showing the structural parts of an insect.

Prepare an insect collection of different insects of significance to agriculture or horticulture.

Identify to genus level, the insects collected.

Compare the structural differences between different types of insects.

Describe the life-cycle of an insect species.

Explain how an understanding of insect life-cycle can be applied to pest control.

Describe the life-cycle of a fungal disease species.

Explain the physiology of tree decay processes, including compartmentalisation.

Explain aspects of fungal biology, for different types of fungi, which are of horticultural significance,  including:

  • Phytophthora
  • Sclerotinia rot
  • Peach leaf curl (Taphrina deformens)
  • Powdery Mildew
  • Pythium.

List environmental problems which affect plant health and their symptoms.

Describe the affect of air pollution on different plants.

Identify nutritional deficiency symptoms in specified situations.

Develop a fertiliser program in response to a specified nutritional problem.

Distinguish between the affects of water deficiency and water excess on plant health.

Explain how to diagnose damage by various non-insect pest problems, including:

  • Nematodes
  • Slugs and snails
  • Mites
  • Millipedes
  • Larger animals such as rabbits, possums or birds.

Explain how to control different non-insect pests with both chemical and non-chemical methods.



This course builds on Horticulture I and Horticulture II but may also be taken as a stand-alone unit; It does however assume assumes some general horticulture knowledge or learning. Upon completeing this course you will be able to demonstrate a higher level of understanding of plant pest and disease problems through awareness of the biology of pest and disease cycles. Understanding thse fundamentals is imperative to setting up programs for prevention and control. The course is suited to people working in:

General horticulture
Garden maintenance
Parks & gardens
Garden conservation
Garden tourism
Nursery & propagation  


Meet some of our academics

John Mason Parks Manager, Nurseryman, Landscape Designer, Garden Writer and Consultant. Over 40 years experience; working in Victoria, Queensland and the UK. He is one of the most widely published garden writers in the world; author of more than 70 books and editor for 4 different gardening magazines. John has been recognised by his peers being made a fellow of the Institute of Horticulture in the UK, as well as by the Australian Institute of Horticulture.
Maggi BrownMaggi is regarded as an expert in organic growing throughout the UK, having worked for two decades as Education Officer at the world renowned Henry Doubleday Research Association. She has been active in education, environmental management and horticulture across the UK for more than three decades. Some of Maggi's qualifications include RHS Cert. Hort. Cert. Ed. Member RHS Life Member Garden Organic (HDRA) .
Diana Cole B.A. (Hons), Dip. Horticulture, BTEC Dip. Garden Design, Diploma Chartered Institute of Personnel & Development, PTLLS (Preparing to Teach in the Life Long Learning Sector), P.D.C. In addition to the qualifications listed above, Diana holds City & Guild construction qualifications and an NPTC pesticide spraying licence (PA1/PA6). Diana runs her own landscape gardening business (Arbella Gardens). Active in many organisations including the British Trust for Conservation Volunteers.
Yvonne SharpeRHS Cert.Hort, Dip.Hort, M.Hort, Cert.Ed., Dip.Mgt. Over 30 years experience in business, education, management and horticulture. Former department head at a UK government vocational college. Yvonne has traveled widely within and beyond Europe, and has worked in many areas of horticulture from garden centres to horticultural therapy. She has served on industry committees and been actively involved with amateur garden clubs for decades.

Check out our eBooks

Getting Work in HorticultureFind out what it is like to work in horticulture; how diverse the industry is, how to get a start, and how to build a sustainable, long term and diverse career that keeps your options broad, so you can move from sector to sector as demand and fashion changes across your working life.
WeedsA good cross section of of common weeds are illustrated and reviewed. These are plants that occur in many parts of the world, and some are not always weeds.
Plant Pests & DiseasesThis is a great guide to understanding, identifying and treating problems in your garden. Discover how to systematically examine and determine what is wrong with plants. Read about all of the main types of pests, diseases, and other problems that can occur, from frost damage to viruses. 197 pages
Landscaping & Gardening in the ShadeThe ‘Landscaping and Gardening in the Shade’ ebook explain what you need to know about designing a shaded garden. It will go through specific plants you could use, how to care for them and different plant varieties that will give you a great shaded area.