Many growers ask the question: What is the cost per hectare for treatment for a pest such as mites? Are chemicals or biological control agents more expensive?

To answer that question we need to explore what is meant by “expensive”. The initial purchase price for biocontrol agents may be more than for chemicals but the benefits of using biocontrol agents that establish, breed up and disperse through the orchard often provide greater economic returns than a pesticide application. There are many costs to factor in that are difficult to quantify such as:

• when you put on a pesticide and then you get a pest resurgence, or development of a secondary pest outbreak, then that’s a cost associated with putting on the initial pesticide application.
• Some biocontrol agents will persist for a long time in the orchard after being released (often depending on what chemical are subsequently used) and so may provide benefits throughout the season and in years to come, resulting in the cost being spread across seasons
• When you look at the total cost of producing fruit, the cost of releasing biocontrol agents is a very small component. Access to markets and gaining a higher price for fruit produced under a system that doesn’t use hard chemicals can outweigh the costs.

A very rough, approximate cost of releasing biocontrol agents is somewhere between $300 to $900 / ha. Species such as Trichogramma cost less at approximately $60/ ha to release. There are however also many other biocontrol agents already working in orchards without having been released. These are naturally occurring and include mite-eating ladybirds, aphid eating hover flies, carabid beetles, parasitoid wasps, and spiders. Poor choice of pesticides can decimate these beneficial species and lead to pest outbreaks that require more sprays to control the pests.

If you establish the population early on before the pest is a major problem then you don’t need to release as many and hence the cost/ ha is less.

So, a simple cost / ha answer is not the whole answer.

Generally using biocontrol agents is not done based on a question of saving money, but rather implementing sustainable pest management.

Article reviewed by Paul James (Lenswood Co-Operative)