Overview: Pests, diseases and disorders

This page provides a diagnostic guide and key reference for pests, diseases, and disorders affecting vegetable crops in Australia. The hyperlinked topics provide further detailed information about the pests, diseases, disorders – their identification, types, management, and source of information and related tools.

Vertebrate pests:

Vertebrate pests include birds, mammals, or reptiles that cause damage to agricultural crops. A number of introduced animals – including rabbits, feral cats, foxes, house mice, wild dogs, Indian Myna, and pigs – have established large and widespread populations in Australia and are pests to crops and livestock.

Sucking pests

Sucking pests include aphids, leafhoppers, thrips, whitefly, flies, bugs, and mites.

Chewing and biting pests

Chewing and biting pests include Helicoverpa and diamondback moth (DBM), caterpillars, beetles, slugs, and snails.

Slugs and Snails:

Slugs and snails are major pests in most horticultural crops. They are invertebrate pests. Both of them are similar in structure and biology, except that snails have an external, spiral shell which is absent in slugs. Once established, the pest can survive in the soil between crops unless the lifecycle is broken.


Nematodes, or ‘eelworms’, are small, non-segmented worms that live in soil, which cannot be seen with the naked eye. They are only 50 microns in diameter and about 1 mm long or less. They feed on fungi, bacteria, and other soil organisms, together with plant cells. In some cases, they also allow fungal rots to enter that destroy the roots. While most nematode species have a beneficial role in the soil, some species are pests and impact agricultural production.


Weeds are invasive plants with the potential to reduce agricultural productivity, displace native species and contribute to land and water degradation. They have significant economic, environmental, and social impacts. Weeds compete with agricultural crops for plant nutrients and water and are one of the most significant sources of pests and disease

Plant diseases and disorders

Different types of plant diseases and disorders include:

Fungal diseases

Fungi constitute the largest number of plant pathogens and are responsible for a range of serious plant diseases. Most vegetable diseases are caused by fungi. They damage plants by killing cells and/or causing plant stress. Sources of fungal infections are infected seed, soil, crop debris, nearby crops and weeds. Fungi are spread by wind and water splash, and through the movement of contaminated soil, animals, workers, machinery, tools, seedlings and other plant material. They enter plants through natural openings such as stomata and through wounds caused by pruning, harvesting, hail, insects, other diseases, and mechanical damage.

Bacterial diseases

Pathogenic bacteria cause many serious diseases of vegetables. They do not penetrate directly into plant tissue but need to enter through wounds or natural plant openings. Wounds can result from damage by insects, other pathogens, and tools during operations such as pruning and picking. Bacteria only become active and cause problems when factors are conducive for them to multiply. They are able to multiply quickly. Some factors conducive to infection include: high humidity; crowding; poor air circulation; plant stress caused by over-watering, under-watering, or irregular watering; poor soil health; and deficient or excess nutrients.

Viral diseases

Viruses cause major damage to many Australian vegetable crops. They are immobile and are usually transmitted from one plant to another by a living organism called a vector or carrier. The most significant vectors of plant viruses include aphids, whiteflies, thrips, and leafhoppers, which have piercing sucking mouthparts that allow the insects to access and feed on the contents of the plant cells. Viruses can also be transmitted by other insects, mites, nematodes, fungi, infected pollen or vegetative propagating material, contact between plants, and infected or contaminated seeds.

Nutrient and physiological disorders

Nutrient disorders are caused by a lack of plant nutrients, or the presence of nutrients at levels toxic to the plant. They affect the functioning of the plant system. When suffering from nutrient or physiological disorders, the plant exhibits disease-like symptoms; therefore nutrient disorders are sometimes mistaken for a disease. Nutrient disorders may result in a reduction in yield.