Insects and Mites

Insects and mites can cause significant damage to horticulture crops by direct damage to the plant and/or by creating a lesion on the plant, allowing secondary invasion of diseases and other pests. Insects and mites are classified as either above ground (e.g. fruit flies, moths, mites, aphids, thrips, scale, weevils etc.) or below ground (e.g. wireworm, cutworm, earwigs, armyworm etc.) pests.

While all of these pests can cause significant crop damage, some of these pests are also considered to be a risk to the biosecurity of other countries, and therefore can affect market access for Australian produce. These biosecurity / market access pests include fruit fly (e.g. Queensland fruit fly and Mediterranean fruit fly), Fullers rose weevil and Light brown apple moth. Whenever R&D is required to develop market access protocols, it is essential that industry, regulators and researchers coordinate the R&D to provide scientifically valid data packages to minimise any market access restrictions and duplication of investment.

Plant Pathogens

Plant pathogens are fungi, bacteria, viruses and nematodes (see nematology section) that cause disease in plants. These pathogens are either soil-borne, air-borne, seed-borne, or in the case of viruses, transferred to plants via an insect vector (e.g. aphids or thrips).

Since the source of the pathogen varies, the management strategies tend to vary significantly. For example, the control of viruses not only involves the control of the disease on the plant, but also the management of the relevant insect vector/s. It is important to understand that management strategies used for insects and other pests can negatively affect the management of pathogens and vice versa either by impacting on beneficial organisms or by improving conditions conducive to the pest.

Weeds

Weeds are classified as feral plants which are growing ‘out of place’ and therefore are often considered undesirable. In horticulture, weeds can be considered hosts for pest insects and vectors, alternative hosts for pathogens, and plants competing with the crop for resources (e.g. nutrients, sunlight and moisture). Weeds can also interfere with pest management practices, including the obstruction in the movement of biocontrols and shielding the pesticide treatment (e.g. sprays, granules) from reaching the targeted areas of the crop. Weeds can also create difficulties with the harvesting process, either mechanically (e.g. wireweed) or by hand (e.g. thistles, nettles). However, weeds can also be managed in ways that benefit the crop, such as using weeds as habitat for beneficial and predatory insects.

Nematodes

Nematodes are microscopic, unsegmented roundworms that live in the soil. There are many types of nematodes, but it is the plant parasitic nematodes, such as root-knot, cyst and lesion nematodes, that can cause severe crop losses. In horticulture, nematodes are particularly a problem in crops such as carrots and potatoes, whose main production is below ground. Nematodes can cause damage to the crop by either transmitting plant viruses through their feeding activity on the roots or by damaging the roots causing it to deform and stressing the plant, causing secondary infections by soil-borne pathogens. Nematology is a very complex area and has often been ignored by industry funding over recent years.

Vertebrate Pests

Vertebrate pests in horticulture include birds, bats, mice, pigs, possums, rabbits, rats etc. Depending on the population and availability of alternate food supplies, these pests can cause negligible damage to total crop destruction. Damage can either be identified as a direct yield reduction or a reduction in quality or increase in contamination. In some cases, e.g., rats in bananas, it can lead to human health issues. Management of many of these pests need to take into consideration the Federal and State Government protection legislation including the ethical treatment of animals.