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Horticulture 1000
HT1103 - Plant Management 3 - Pests
Healthy plants Diseases


Pests can kill plants, slow their growth and damage stems, leaves, flowers and fruit. A host is the plant on which the pest feeds.

Some pests can also introduce diseases into plants.

There are two main types of plant pests: chewing and sucking.

Chewing pests

Caterpillars are common chewing pestsCaterpillars are common chewing pests. This apple shows possum damageThis apple shows possum damage.

Chewing pests tear, bite or chew parts of the plants: leaves, stems or roots.

Pests such as borer and leaf miners tunnel into stems or leaves by chewing.

Rabbits and possums are large chewing pests.


Here are some chewing pests.

Earwig Cricket Grass-grub larva Earwig. Cricket. Grass-grub larva. This feeds on the roots of crops, particularly grass.
Slug Snail Slug. Snail.

Here is the damage caused by some chewing pests.

White tunnels made by leaf miner A chewing pest has made holes in this leaf White tunnels made by leaf miner. A chewing pest has made holes in this leaf.

Sucking pests

These pests have special piercing mouthparts for feeding. The mouthpart sticks into the plant, sucks sap out and pumps saliva into the leaf and stem. Plant tissue is digested and leaves become deformed, stunted or discoloured.


In the photo you can see some aphids. When the mouthparts of these pests penetrate plants they suck out the sap. They can spread viruses as they move the sap from plant to plant.

Aphids also produce honeydew on which sooty mould grows.


Some other examples of sucking pests:

Whitefly Green vegetable bug Whitefly. Green vegetable bug.
Thrips Cricket Thrips. Scale insects.

To control plant pests you must first identify them and then use an appropriate control method. Questions to think about include:

Activity 2A Select whether the damage symptoms are caused by either a chewing or sucking pest.

Activity 2B Test your understanding of pests so far.


Activity 2C Answer the following questions about pests and the damage they cause to plants. Read the information on the insert HT1103A for further information. You might also need to do some extra research of your own to answer the questions correctly. Look on the Internet or use reference books such as Yates Garden Guide from the library.


Activity 2D In each of the photos below, drag the name of the sucking pest that causes the damage described in the table.


Complete Activity 2E in your workbook

Key points   Key points

  • Chewing pests eat parts of plants such as roots or leaves. They include caterpillars, grubs, slugs, snails, and slaters.
  • Sucking pests suck sap and can also transmit viral diseases. They include aphids, thrips, whitefly and mites.

What's next?

Go to: 3 Diseases.

Healthy plants Diseases