The Neutrog R&D team has been working in South Australia’s Century Orchards for a number of seasons to explore how biologicals can be used to improve production with a specific trial relating to the impact of Hull Rot.

Hull rot is a major disease in the almond industry which significantly effects the future productivity of an orchard.

Primarily by the fungi Rhizopus stolonifera, almonds are susceptible to infection from the early stages of hull split through to harvest where the fungal spores access the inner surface of the hull. 

This allows the spores to survive and reproduce by accessing the moisture and nutrients present in the hull.

From here the spores can spread and quickly infect other areas of the orchard.

Hull rot strikes are the first initial sign of hull rot infection and are caused by the acid by-products produced by the fungus, which are then spread through the vascular system of the tree.

This causes spur death and twig dieback referred to as ‘hull rot strikes’, reducing fruiting wood for the following seasons which ultimately reduces the future productivity of the orchard.

Hull rot is generally most prevalent in orchards with high fertiliser and water input which allows the fungi to thrive.

Therefore, at hull split, growers may implement management controls, such as reducing water, to apply a moderate amount of stress to the orchard.

This reduces the moisture in the hull available to the fungi and therefore can assist in lowering the prevalence of hull rot.

Alternatively, or in conjunction with these management controls, growers may apply a fungicide (such as Merivon) at the beginning of hull split in an effort to protect the tree and crop.

Another option is the use of potassium silicate (which has many uses in agriculture) but can also be used is also a natural, non-synthetic fungicide.

When applied as a foliar spray, the potassium silicate, enters the plant between the epidermal cell layer, creating a silicon matrix and forming a physical protective barrier. This barrier protects the tree from fungal infection by numerous pathogens.

Century Almonds ran a trial in 2021-2022 testing the efficacy of potassium silicate for hull rot suppression.

In the 2022-2023 season, a more extensive trial was undertaken to assess a range of different products including potassium silicate and Neutrog’s biological inhibitor, POPUL8.

The trial consisted of five blocks: 

• control sprayed with Merivon to follow the orchard standard for the season
• potassium silicate only
• combination of Merivon and potassium silicate
• potassium silicate and Neutrog’s biological hull rot inhibitor
• singular application of Neutrog’s biological hull rot inhibitor

Results indicated potassium silicate, when applied in conjunction with Merivon, is the most effective in significantly reducing the number of hull rot strikes per tree, when compared to applying only Merivon which is standard practice in the orchard.

However, the trial also showed that Neutrog’s biological inhibitor POPUL8 was the second most effective.

The Neutrog R&D team is looking forward to continuing to work with the Century Orchard team.