Winter sanitation and ground management practices for navel orangeworm (Lepidoptera: Pyralidae) control in pistachios

Authors: DAANE, KENT - University Of California Berkeley; YOKOTO, GLENN - University Of California Berkeley; Krugner, Rodrigo; Siegel, Joel; HAVILAND, DAVID - University Of California - Cooperative Extension Service; WILSON, HOUSTON - University Of California, Riverside; Burks, Charles

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/21/2026
Publication Date: 3/28/2026
Citation: Daane, K.M., Yokoto, G.Y., Krugner, R., Siegel, J.P., Haviland, D.R., Wilson, H., Burks, C.S. 2026. Winter sanitation and ground management practices for navel orangeworm (Lepidoptera: Pyralidae) control in pistachios. Journal of Economic Entomology. Available: https://doi.org/10.1093/jee/toag061.
DOI: https://doi.org/10.1093/jee/toag061

Interpretive Summary: There are 640,000+ acres of pistachio grown in California and this year’s crop is valued at over $3.5 billion dollars. The primary moth pest of pistachio and almond in California is the navel orangeworm, and control of this pest requires up to $260/acre in management costs, with losses causing up to $100M in damage per year in pistachios and $800 million in damage per year in lost sales in almonds over the past two years. Nuts are left behind after harvest and these nuts are given the colorful name “mummies” by the growers. Their destruction is essential because the nuts left in the tree and fallen on the ground provide both shelter and food during the next crop year. Sanitation serves as the foundation for managing navel orangeworm and reducing damage, but this practice is more complex in pistachio than almond. Simply put, pistachio mummies are hard to destroy because of their hard shell, and while some mummies can serve as a food source, many are empty or closed and are not a problem. Growers are divided on the amount of resources needed to both remove pistachio mummies from the tree and destroy those on the ground. This study demonstrated that navel orangeworm also develop in mummy kernels on the ground, and that females lay eggs on nuts on the ground as well as in the canopy during the spring. Their behavior reinforces the need to destroy mummies on the ground and justifies the cost of this effort. These data demonstrate that greater emphasis on estimating and destroying carryover of ground mummies is needed to improve control of this pest. This analysis will help growers and extension agents develop new strategies to improve navel orangeworm control, and that mummy destruction, which does not involve the use of insecticides, can play a key role in future area-wide integrated pest management programs for both pistachio and almond.

Technical Abstract: The navel orangeworm, Amyelois transitella (Walker) (Lepidoptera: Pyralidae), is a key pest of California tree nuts, whose control programs include the winter sanitation of unharvested nuts (mummies). A five-year survey of commercial pistachio orchards in California showed a positive association between the number of mummies per tree and the number of A. transitella eggs deposited during the first flight in 3 of 5 years and a negative association in 1 of 5 years. Factors that impacted overwintering A. transitella included the number of closed or empty nuts lacking a kernel (blanks), infestation levels (range 0.4 – 13.5%) and the number of mummies on the ground (range 11.2 – 90.6 mummies per m2). There was higher moth emergence from nuts on the berm than from the row middles. Mowing, discing, or rototilling the row middles reduced adult moth emergence, with raking nuts into the row middle being the most effective. Neonate A. transitella utilized both open pistachio mummies, and insect damaged or split mummies; closed shell mummies and new crop undamaged nuts were not used. Oviposition varied by egg trap location with the fewest eggs deposited on the ground (20.1 eggs per trap per week), and similar numbers deposited at 2.5 m (mid canopy, 33.3 eggs per trap per week) and at 4.25 m (upper canopy, 32.3 eggs per trap per week) above ground. These findings underscore the importance of winter sanitation that includes ground mummies in pistachios to reduce the standing population of A. transitella and that a complete program includes the removal or destruction of ground mummies.