By Dr Mike Morris, Plant Health Products

As forestry practices look towards safer and more environmentally friendly solutions for pest and disease management, the use of biological control provides a suitable option.

Biological control of forestry pests in South Africa has been active for more than 100 years. This has largely involved the introduction of natural enemies of forestry pests (such as parasitic wasps) from the pest’s country of origin. After its introduction, the natural enemy will usually reproduce and multiply on its own. This form of biological control is known as “Classical Biocontrol”.

Biological products based on micro-organisms, such as fungi and bacteria, provide another biocontrol option, which can be applied in much the same way as chemical pesticides and fungicides. Biological products have many advantages over their chemical counterparts:

• they are toxin-free and workers can re-enter and work in the treated areas immediately after application.
• in some cases, they may multiply in the field and infect future generations of a pest.
• and they have little effect on other natural enemies (such as parasitic wasps) of pests and beneficial insects (such as bees).

The organisms used in most biological products are already naturally occurring and active in healthy, untransformed environments.

Biological products have multiple applications within the forestry industry; they can be used in both plantations and in nurseries to control aerial fungal diseases such as Botrytis and powdery mildew, and pests such as caterpillars, mites and beetles. In addition, products are available that are applied to the soil and provide enhanced germination, seedling growth promotion and control of root disease such as Fusarium.

Biological control is a growing industry, with great potential for future product development. Future products already on the horizon include an active hyperparasite of wattle rust present in South Africa, which has the potential to be multiplied and developed into a biological control product.