Hull rot

Description

The withering of leaves a few weeks before harvest may be the first indication of hull rot. Examination of the fruit on that shoot will reveal grey to black sporulation inside the hull and around the shell. Rhizopus can produce a toxin that kills the leaves and spurs, and can also cause excessive gumming where the nut joins the spur. Affected nuts will become stuck in place and not be shaken off the tree at harvest. That leaves black, mummified nuts and leaves stuck to the tree to overwinter and affect the next season’s fruit.

Control

Until 2015, there was no fungicide registered for the management of hull rot in almonds available in Australia. Now Luna® Sensation is registered for suppression of the disease. Applied to the point of run-off at early hull-split and again at the first sign of infection, Luna Sensation can be expected to reduce the percentage of nuts infected and retained on the tree after harvest.

Other suggested protective practices include removing the blackened mummies, picking up windfall nuts early, reducing irrigation for a two-week period at the onset of hull-split, thinning the canopy to improve airflow, and avoiding nitrogen applications after kernel development.