Hull rot isn’t a warning to sailors, but your almond tree may be at risk.
If you grow almonds, your tree goes through several stages before producing a crop. As deciduous trees, winters are spent bare and quiet. In late winter or early spring, a riot of colorful blossoms unfolds, followed by leafing out.
Those flowers will fall, and fuzzy green almonds will start to grow. As they ripen, they get fat. Ultimately, the hulls dry and split open. When that occurs, hull rot may invade the nuts, threatening the life of your tree.
Hull rot is a fungal disease initiated by Monilinia, Rhizopus, and Aspergillus niger. Aspergillus niger also causes sooty mold. If you notice leaves on shoots withering and dying, look more closely.
Hull rot symptoms
You may see brown areas on or in the hull (Monilinia). You may see black fungal growth inside the hull, between the hull and the shell, or on either side of the edge that opens (Rhizopus stolonifer). Or, you may see black spores between the hull and shell (Aspergillus niger). Each of these is a type of hull rot.
These fungi produce toxins that kill fruiting spurs and the twigs to which they are attached. Almonds on infected branches are more difficult to remove than healthy nuts. Ultimately, shoots, strikes (fruiting wood), and lower limbs die back.
Hull rot prevention and management
Healthy trees are less likely to become infected in the first place, so care for almond trees properly with these tips:
Trees infected with hull rot need help from a professional arborist. The fungicides effective against hull rot are generally unavailable to the public.
Hopefully, your almond tree will never become infected with hull rot.
You can grow a surprising amount of food in your own yard. Ask me how!
To help The Daily Garden grow, you may see affiliate ads sprouting up in various places.
You can also get my book, Stop Wasting Your Yard!