Where there is intensive farming, there is also high disease pressure from increasingly limited control options, be it chemical or biological. This includes the almond industry which is under pressure to find alternative and sustainable solutions to reduce the impacts of almond hull rot.

Primarily by the fungi Rhizopus stolonifera and Monilinia fructicola, 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.

For almond growers, almond hull rot is a major concern due to its significant impact on the future productivity of an orchard, and currently there are only limited and low efficacy control measures available.

“Almond hull rot not only effects the nut leading to downgrade of the quality, but it also causes damage which results in lead loss, die back of branches, and is estimated to cost growers approximately $3,000 per hectare in revenue and damage repair,” says Dr Uwe.

“Within our collection of microbes at Neutrog we had a number of isolates (inhibitors) which showed good inhibition and killing of these pathogens in a laboratory setting.  Therefore, a trial was undertaken by an almond grower in the Riverland using a biological control agent formulated by Neutrog, which was sprayed into the canopy of the trees.  This biological agent showed a two-to-three-fold reduction in the incidence of almond hull rot above the currently used chemical fungal control.”

This trial caught the eye of almond growers in California. who are now conducting their own trials using the biological control agent made by Neutrog.

California provides approximately 80% of the world’s almonds, generating US$19.6 billion gross revenue per annum. To achieve this, the growing area in California stood at 1,630,000 acres (660,000 hectares) in 2022.

“We have recently shipped several litres of this bio control agent to the USA and are eagerly awaiting the results from this trial.”