Plant Protection

Study pest and disease control - Horticultural Correspondence College

Course CodeBHT207
Fee CodeS3
Duration (approx)100 hours
QualificationStatement of Attainment

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A course for technicians, gardeners and horticulturalists that need to know in detail horticultural pest and disease identification and control, with chemical and biological solutions and safety procedures and practices.


  • Sanitation - maintaining good hygiene
  • Physical control methods e.g. mowing, slashing, burning, flooding, hand removal, physical barriers (ie. netting, fences), etc.
  • Using plant varieties that are resistant to pests and diseases
  • Biological controls
  • Chemical controls (artificial and naturally derived).
  • Soil drenches/dips

This course takes a "holistic approach, giving appropriate consideration to all of these "methods", without bias toward any particular method

Lesson Structure

There are 10 lessons in this course:

  1. Introduction: scientific names, terms, diagnosing problems
  2. Control Techniques: biological and chemical techniques, alternative methods
  3. Chemicals: characteristics of chemicals
  4. Identifying Diseases: symptoms, fungi and viruses and other pathogens
  5. Disease Control: life cycle of fungi
  6. Insect Classification: biology and insect classification
  7. Insect Control: how to control pests
  8. Non Insect Pests: nematodes, snails, centipedes, etc.
  9. Chemical Weed Control: weed identification
  10. Non‑chemical Weed Control: natural control methods

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 broad category which a plant health problem belongs to.
  • Explain a range of methods for controlling plant problems.
  • Select appropriate chemical pesticides for different problems.
  • Identify the symptoms of different plant diseases, including most common and some uncommon problems, in your locality.
  • Develop procedures to control specific plant diseases.
  • Identify different insects, including significant taxonomic orders, common pest species, and some less common pest species
  • Determine appropriate methods to control different types of insects.
  • Identify different non-insect pests found in the learner's locality.
  • Determine appropriate control methods for different non-insect pests.
  • Identify different non-insect pests found in the learner's locality.
  • Determine appropriate control methods for different non-insect pests.
  • Manage the control of different types of weed problems.


Problems can be looked at as being in one of three possible categories:

1. NUTRITIONAL ‑The plant has either too little or too much of one or several particular nutrients available to it.

2. ENVIRONMENTAL ‑The environmental conditions are not suitable e.g. heavy rain, flooding, frost, snow, hail, sunlight, etc.

3. PATHOLOGICAL ‑One or several organisms are interfering with the health of the plant (such organisms are called "pathogens").

It requires a great deal of knowledge and expertise to be able to diagnose plant troubles. Do not expect to develop such ability quickly.

The first and perhaps most important skill to develop is an ability to inspect a plant and look for the tell tale symptoms which can provide an indication of what might be wrong.

The table below provides a systematic approach to inspecting plants which you suspect, (or know) might be unhealthy. You should look at each of the "items" one at a time, following the guide given by the "method of inspection" column.






View old and young leaves

‑both and underneath above




Leaf drop

Insects ‑live or dead


View top to bottom, push foliage out of the way. Binoculars for tall plants.

Stem rot

Spots or other markings.


Side shoots

Thin or thick stems.


Stand back and view, look at where strong growth is and direction of buds

Is it balanced

Appropriate or type of

plant (bushy for shrub...strong

terminal growth for tree..etc)

Growth rate


Feel surface of soil, push finger 2‑4cm below surface

Remove plant from pot


Hardness, root



Wet/dry spots


View holes at bottom of pot, Remove plant from container,

View surface of soil.

Root tip burn, Rotting,

Distribution of roots ‑even?

Discolouration of Growing tips




1. Wilting

a/ Insufficient water in the soil

b/ Leaves drying out faster than the water can be taken up (too hot)

c/ Something stopping water going up the stem (eg: borer, disease, etc. in lower part of plant). TAKE


2. Yellow Leaves


a/ Lack of Nitrogen (feed with a nitrogen fertilizer)

b/ Lack of Nitrogen caused by wet soil ‑ wet soil stops nitrogen being taken into the plant (improve drainage or cut watering).

c/ Chemical damage

d/ Soil very dry


a/ Iron deficiency

b/ Other nutrient deficiency

c/ Chemical damage


3. Look to see if damage is distributed evenly over plant.

  • On one side only
  • On the top only
  • On the most exposed parts


4. Look to see if damage has only just happened....or is past?

  • The appearance of the growing tips tells you the current condition.
  • Young shoots indicate a healthy plant overcoming past problems.
  • Excessive side shoots lower down indicates disruption of hormone flow in the plant, or some other problem in the upper parts of the plant.


Plants are prone to a range of pests and diseases whether they are grown as crops or ornamental plants. Not only do they have to fend off these invaders but they also have to compete with other plants for air, nutrients and water. Whichever environment plants are grown in, they can be helped to overcome these problems through good techniques and strategies of management. In this course students learn about a range of different pests, diseases and disorders of plants, and how to tackle them. They also learn about weeds and how to identify and remove them. This is an ideal introductory course which covers a range of problems.
This course is suited to people working in:

  • Garden maintenance
  • Parks & gardens
  • Landscaping
  • Garden restoration

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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
Rosemary Davies

Leading horticultural expert in Australia. Rosemary trained in Horticultural Applied Science at Melbourne University. Initially she worked with Agriculture Victoria as an extension officer, taught horticulture students, worked on radio with ABC radio (c
Adriana Fraser

Over 30 years working in horticulture, as a gardener, propagator, landscape designer , teacher and consultant. Adriana has spent much of her life living on large properties, developing and maintaining her own gardens, and living a semi self sufficient li
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