In the world of mango cultivation, optimising flower development and retention is crucial for ensuring successful fruit production and maximising yields, Zenon Kynigos* writes.

When a season’s outcome depends on abundant flowering and high fruit-set, several key factors come into play, including the role of calcium, cytokinins, and antioxidants.

These elements have a profound impact on the growth, quality, and longevity of mango flowers. By understanding and harnessing the effects of calcium, cytokinins, and antioxidants, Australian growers can unlock the full potential of their mango orchards and achieve optimal results.

Mango growers using a multi-pronged approach targeting these elements in South Africa, Zambia and Zimbabwe during the past five years have consistently reported amazing results with a significant reduction in flower drop and an abundance of flowers followed by good harvests.

The significance of calcium

Calcium, an essential nutrient, holds immense significance in mango orchards. It plays a pivotal role in flower development, pollination, flower retention, and fruit quality. Adequate calcium levels support the growth and proper formation of floral organs.

Importantly, calcium reduces premature flower drop, thereby enhancing flower retention and increasing the chances of successful fruit set. By maintaining optimal calcium levels, growers can produce high-quality mangoes that meet market standards.

Harnessing the power of cytokinins

Cytokinins, a class of plant hormones, exert a significant influence on flower development and retention in mango trees. These hormones promote cell division, expansion, and differentiation during flower development, ensuring the proper formation of petals, sepals, stamens, and pistils.

By stimulating cell division, cytokinins contribute to the overall size and structure of mango flowers.

Cytokinins also regulate the balance between growth and senescence signals within the flowers, extending their lifespan and maximising pollination opportunities. The development of healthy and functional ovules, essential for successful fertilisation and fruit development, is also facilitated by cytokinins.

So, by managing cytokinin levels, growers can optimise flower development, increase flower retention, and ultimately achieve higher fruit yields.

The role of antioxidants

Mango trees often face environmental stressors such as high temperatures and drought, which can adversely affect flower development and retention. Extreme weather such as the droughts, floods, heatwaves, and cyclones experienced in Australia’s mango-growing regions in recent years, contributed to plant stress and impacted flower development and retention in some areas.

Flowers are particularly susceptible to oxidative stress when plants are exposed to stressors such as heat, cold, salinity, drought, or high UV light. When plants experience stress, they produce reactive oxygen species (ROS) that can damage cells and reduce flower quality.

The build-up of toxins in the plant’s cells causes flowers to drop off. Here is where antioxidants come to the rescue. These powerful compounds neutralise harmful reactive oxygen species (ROS) and protect flowers from oxidative damage.

Excessive oxidative stress can lead to tissue degradation and poor flower quality. By reducing oxidative stress, antioxidants safeguard flower cells, ensuring healthier development and improved flower retention.

Additionally, antioxidants help maintain hormonal equilibrium, counteracting the negative effects of oxidative stress. By preserving cellular health and supporting efficient photosynthesis, antioxidants contribute to optimal flower development and increased energy allocation to the flowers.

Abiotic stress can reduce yields by more than 60 per cent on average and it’s believed 80 per cent of global orchard yield loss is due to abiotic plant stress. While growers cannot predict or control the weather, practices which replicate, and boost plants’ natural defence mechanisms will mitigate these effects and give growers some peace of mind during the critical flowering period.

Practical applications in orchard management

Growers can incorporate various practices and products into their orchard management strategies to optimise flower development and retention in mango trees. Calcium-rich fertilisers or soil amendments can be applied during establishment and maintenance stages to maintain adequate calcium levels.

Foliar sprays of high-efficiency calcium absorption products can be used during critical growth stages, particularly before and during flowering, to enhance calcium uptake.

Additionally, the application of cytokinin-promoting products can optimise cytokinin levels, resulting in more flowers, improved flower development and retention. Incorporating antioxidant-boosting products into orchard management practices can mitigate the impact of environmental stressors and enhance flower quality and longevity.

ProdOz, an Australian supply company, has partnered with Levity Crop Science, a UK-based company, to offer Australian mango and other orchard growers access to Levity's patented product line-up.

Developed with cutting-edge technologies, the products address common plant physiological issues for targeted results. The products include Albina for calcium absorption, Lono for promoting cytokinin production, and Indra for boosting antioxidant production. Used together, they target crop quality, maximum yields and are universally effective in all orchard crops.

Insights from Southern Africa

In Southern Africa, mango flowering occurs during the transition from cold to warm weather in July and August. However, as the temperature rises in October, mango growers face a challenge known as November fruit drop, which is caused by high heat build-up.

To address this issue, the use of Indra has proven to be effective in minimising fruit drop during this period. The application of Indra involves three treatments, with 1.5L per ha applied in mid-October, mid-November, and mid-December. This practice has been shown to significantly reduce November drop.

Additionally, a foliar application of Lono (5L per ha) mixed with Albina (1L per ha) can help improve flower quality and reduce fruit abortion after setting. In South Africa, a fruit enhancement program has been implemented for mangoes, avocados, macadamia, citrus, and lychee.

This program involves applying the mixture mentioned above three times at specific intervals depending on the crop. For mangoes, avocados, lychee, and citrus, the applications are done 90 days before flowering, 60 days before flowering, and at 15 per cent flowering.

For macadamia, the applications are done 120 days before flowering, 90 days before flowering, and at 15 per cent flowering. This program not only increases flower numbers but also affects bud differentiation, promoting the transition from vegetative or dormant buds to reproductive ones.

*Zenon Kynigos is a crop science technologist with ProdOz International, based in Melbourne. For more information contact him on 04676 28493 or visit the Levity Crop Science website at levitycropscience.com.au