Like tiny winged warriors descending from the sky to fight the dreaded navel orangeworm, the USDA’s Plant Protection and Quarantine program is developing its own army by propagating sterile moths by the millions.
“The Sterile Insect Technique is designed to release sterile insects into the wild, hoping they will find one another and mate with resultant no offspring,” says Eoin Davis, Director of Field Operations at the Phoenix (Ariz.) Rearing Facility, a site that has become central in the biological warfare against the worm that damages almonds and pistachios.
For many years, the Phoenix facility has proven pivotal in using sterile insect technology to combat serious agricultural pests. Among its targets was the pink bollworm, one of the most destructive cotton pests in the world. Instead of spraying conventional pesticides, PPQ and its partners agreed to use an integrated, non-chemical approach to eliminating the pest, the USDA’s Animal and Plant Health Inspection Service explains.
The approach included planting transgenic cotton, using insect pheromones to disrupt mating, and releasing sterile insects to prevent reproduction. At the height of the program, the facility was distributing more than 5 million moths per day in California alone, and more than 30 million across all affected states, Davis has said.
“That same facility was the arsenal that western cotton growers used to rear pink bollworm moths many years ago where larvae received non-lethal doses of irradiation that rendered them infertile before they were dropped into cotton fields and eradicated the bollworm,” said K. Cecilia Sequeira of USDA APHIS.
Lab pivots to NOW
With the bollworm eliminated, the lab pivoted about five years ago to the mass rearing and sterilizing of navel orangeworm moths, with daily production now upwards of 1 million. In late 2019, then-President Donald Trump bolstered funding for the project by approving a $6 million federal spending bill after repeated visits and conversations with tree nut industry groups leading three delegations of lobbyists, support members and members of California’s congressional delegation who emphasized the critical need to bolster NOW research.
UDSA National Policy Manager Karen Maguylo also credits funding from the pistachio industry for enabling the project.
“Those sterile moths are shipped to California where the Department of Agriculture and the pistachio industry are doing airborne releases over isolated trial almond and pistachio groves in the San Joaquin Valley,” she said.
To date, some 125 million moths have been produced, and, Davis said. “We’ll target about the same production level again … when the program resumes new sterile moth creation in March 2021.”
“In this phase of the pilot, we focused on being able to produce and reliably deliver sterile moths to fight NOW populations,” said Earl Andress, supervisory entomologist. “As far as their impact in that fight, we’ll determine that in a different phase of the program.”
Analysis suggests success
Though the COVID-19 pandemic slowed production and then caused the facility to close for three days last spring, initial analysis indicates creation of a successful mass production environment has been achieved.
“We’re happy with what we’ve been able to make work on a large scale of consistent production. We met our shipping goals and had sterile moths available continuously through the 2020 season available for shipment and release,” Davis said.
A USDA progress report noted, “daily protocols were adjusted to maximize production (including) more efficient rearing techniques involving egg density per tray to produce the maximum number of moths per unit of floor space.”
“Things got better as the season progressed and we discovered how to better control the temperature of the moths during transport and awaiting release,” Davis acknowledged. “That measurably improved the quality of the sterile moths available for the field.”
Added Andress: “We had a couple of hiccups, but we saw improvement in the moth performance and recovery of those we released. Things are looking good going forward.”
“As we close out the year,” noted Davis, “I remain optimistic that SIT will be a viable tool for California nut growers.”
“Sterile insects aren’t a silver bullet,” said Maguylo, “but they will complement other area-wide control measures like sanitation and coordinated pesticide applications to help sustain effective, long-term pest management.”
For more news on tree nuts as reported by growers and farm advisors, subscribe to the Tree Nut Farm Press e-newsletter.