The Australian macadamia industry is currently navigating a challenging chapter. While growers have rebounded from multiple natural disasters in recent years to deliver an abundant, quality crop, this is being accompanied by rising costs and the softest farm gate prices in more than a decade.

Most macadamia growers are now faced with the challenge of rationalising all costs of production including in the key areas of nutrition, canopy management, harvest and post-harvest and pest and disease management.

The AMS spoke with consultant Jarrah Coates from Coates Horticulture about how growers might manage their pest and disease programs this season.

With the challenging season that growers face, what are some short-term reactions to pest and disease cost savings which can result in long-term, multi-season impacts?

With nut prices falling to below costs of production, growers may look to cut corners to reduce costs where possible. One option growers might look to is to buy the cheapest chemical controls available. If you are considering this, remember that chemicals are registered differently depending on state regulations (either specifically for the target pest or the crop). Off-label use is illegal.

Another option some growers might consider is to abandon the crop entirely. Apart from potential crop failure for the immediate season, more long-term pest management issues may arise. Pest populations are more likely to build up and carry over to future growing seasons.

While newer, selective chemistry can be more expensive on face value, what are the hidden costs in reverting back to only using broad spectrum synthetic pyrethroids and organophosphates?

Cheaper chemistries include some of the products in the synthetic pyrethroid and organophosphate chemical groups. Chemicals in these groups are generally broad-spectrum controls, i.e. they have an effect on a wider range of insects. Repeated use of such products can result in a number of problems. Before deciding on chemistry to use, note the following:

- Efficacy of treatment. While some more targeted chemicals might be more expensive for a single application, only a single treatment might be needed for effective control, thus are likely to be economical options when compared to broad-spectrum chemicals that might need to be applied more than once. Good examples are well-timed treatment of macadamia seed weevil and macadamia lace bug.

- Significant impact on or decline of non-target insect populations. Non-target populations include neutrals, pollinators, parasitoids and predators, all of which can perform important roles in your orchard, for free. Management and crop protection should focus on encouraging these insect populations.

- The occurrence of pest flare. Removing parasitoids and predators (natural enemies) of specific pests can result in pest flare, where minor pests become major pests as a result of unnecessary or poorly timed chemical treatment. The most common examples in macadamia orchards are flared populations of thrips, mites, feltid coccid (and other scales), and to a lesser degree, aphids and mealy bugs.

- Pest resistance. Repeated use of any chemical product or grouping can result in pest resistance. Many cropping industries have experienced resistance problems, which have had serious ramifications for effective pest and disease control. It is important to reduce and rotate applications from different chemical groups to help avoid resistance.

In your experience are there inefficiencies in pest and disease management which growers can address to get better bang for buck this season?

Aim to build beneficial and natural enemy populations in your orchard to buffer against pest incursions and potentially reduce the need for pest control. Consider planting an inter-row insectary where rows have been removed or in other suitable areas in the orchard.

Make sure your spray unit is functioning to the optimum with both calibration and spray coverage. Have an up-to-date inventory of the chemical shed.

It is important to avoid calendar spraying. Spray decisions that are not made based on monitoring data can result in spray applications that are not necessary as well as unnecessary use of resources, damage and increased input costs. Remember, just because the neighbour is spraying does not necessarily mean you also need to.

Some growers might try to save costs by monitoring less. How can monitoring more can save money and orchard resources?

Crop monitoring makes up a relatively small cost in the crop production big picture, something that has been demonstrated in recent industry benchmarking.

Regular crop monitoring is also an important investment as it provides data for informed decision making. This can help with precision timing for application of controls and measured implementation of appropriate resources, resulting in optimum pest and disease management, reducing environmental damage while maximising crop productivity.

This article was first published in the Australian Macadamia Society News Bulletin Winter 2023 edition.