Dormant Trees, Busy Farmers

Posted January 17th, 2018

It’s winter time and harvest is over, but the work for California Almond farmers isn’t done. Like many other types of trees, almond orchards lose their leaves during winter and rest, a time known as dormancy. Once the leaves have fallen from the branches, some farmers find that not all of the nuts were removed at harvest. After gauging the number of nuts remaining, many farmers undertake an important task – removing mummy nuts.

Not to be confused with an out-of-the-box Halloween costume, mummy nuts are what almond farmers call the crop that remain in the trees after harvest. The normally fuzzy, green outer hull darkens and the nut remaining inside becomes a desirable food source for worms and moths known as navel orangeworm. These bugs then spend the winter inside the almond’s shell, feeding on the almond inside and emerge in the spring of the following year to find additional food in the form of the next year’s almond crop.


By removing these mummy nuts, farmers outsmart the bugs, eliminating their comfortable winter homes and decreasing the number of navel orangeworm that will be in the orchard the following year.

So how do they do it? One way to remove mummy nuts is by bringing back into the orchard some of the equipment used to harvest the crop. A mechanical shaker grabs the trees’ trunks, shakes the tree for a few seconds, and the remaining nuts fall off. The other approach, called poling, relies on people walking through the orchard and manually knocking mummy nuts off branches with long bamboo poles.


After both mummy removal methods, farmers run large mowers through the orchard to chop up the nuts that have fallen to the ground, eliminating the bugs’ winter habitat.

This form of natural pest control puts farmers ahead of the pest pressure, an important consideration given that navel orangeworm is the single most impactful pest that targets almonds.

The California Almond community has been funding research into pest and disease management for more than 40 years. From this we know when and where harmful insects hibernate, how disease can spread from tree to tree and what conditions make orchards appealing to invading pests. This allows almond farmers to use a balanced, integrated approach to pest management, utilizing nonchemical practices like mummy nut removal along with chemical practices, when needed, to protect the trees, the almonds, neighbors and the environment.

To learn more about this time in the orchard, as well as other parts of almonds’ annual growing cycle, click here and explore the almond lifecycle.


In the Orchard