Macadamia trees are, in fact, native to Australia and can be found mainly in the sub-tropical states of New South Wales and Queensland along the Eastern seaboard of the continent.

It goes without saying then that the trees grown in South Africa thrive mainly along the KwaZulu-Natal coastline.

However, most of the orchard plantings in this country fall outside the preferred climatic environments, which puts the trees – especially those that have been newly planted – at risk. They are particularly susceptible to stress factors such as phytophthora, temperature, frost, wind, drought, altitude, pests, diseases and the health of the soil.

Young trees are particularly susceptible to frost damage. This tree is planted outside Cedara in the KwaZulu-Natal Midlands, where frost is common and frequent

Help your tree to help itself

Growers who have planted their trees in high altitude regions, and where low temperatures are frequent, should focus on boosting the overall health of the plant as its capacity to remain resilient and resist the effects of biotic and abiotic stress depends heavily on underlying root and soil health.

Plants have a built-in immune system and a natural ability to defend themselves. Healthy plant environments, particularly those with a proliferation of beneficial microbes, have been scientifically proven to activate and enhance this system, which is referred to as Induced Systemic Resistance (ISR).

This resistance is commonly included as a ‘mode-of-action’ in biological pest control solutions, for example, Bacillus amyloliquefaciens – a beneficial bacteria, which is used in bio-fungicides and works by activating a signalling pathway inside the plant which then heightens the plant’s immune response, making it better able to fight disease.

A macadamia tree with a Phytophthora infestation, for example, stands little chance against frost because the plant is already compromised and under stress.

Using beneficial fungi (Trichoderma asperellum) and bacteria (Bacillus amyloliquefaciens) helps to build resilience which in turn supports tree growth and guarantees the up-take of water and nutrients at the correct time and in the correct form through the development of a strong root system.

Mechanical strengthening

Science has proven that silica builds resilience and resistance into plants by hardening the outer cell walls of the plant from the roots through to the very top of the tree.

In South Africa, at least 70% of soils are silica (Si) deficient, and in particular those in former sugarcane fields where up to 300kg Si-a-hectare-year would have been drained from the soil by the crop.

Silica has a direct impact on cell strength.

The compound deposits on to plant cell cuticles, forming a mechanical barrier between the plant and the environment. It also reinforces the vascular bundles, keeping them open and leading to a more efficient transport of water and nutrients. Typically, once a tree is frosted it is the breakdown of these vascular pathways that causes irreparable damage. Silica is recommended where any stress event is the primary concern, for example cold tolerance.

The compound should be applied at 5l-a-hectare monthly or at least two to three months prior to any anticipated frost events.

AgriSil K50 is an extremely soluble liquid plant-available form of silica and is efficiently available at comparatively low application rates

Silica also acts as a ‘catalyst’ of natural plant resistance mechanisms in that it triggers ISR. This means where there is sufficient silica available to the plant, resistance responses are more complex and occur more quickly.

Madumbi’s Root Health Programme

The key to developing resilient trees is to provide a healthy soil and soil structure able to facilitate new root development. Organic matter and beneficial microbes have a significant role to play and are critical for promoting root health and plant resilience.

The Madumbi Root Health programme. A combination of four different biological solutions.

Healthy root systems provide a strong foundation for future tree health and production, ultimately leading to increased income.

The Madumbi Root Health programme combines increased growth-promoting microbes with nutritional support to optimise root health and development, nutrient update and disease suppression. This holistic, integrated approach induces the plants’ inherent resistance mechanism or Induced Systemic Resistance (ISR).

In summary, Madumbi’s Root Health programme is designed to build resilience in the trees.


Mark Hutton is the Business Development – Bio Specialist at MadumbiSA

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