Adding fuel to a state agricultural department plan already under fire, spraying seven heavily populated northern California counties to eradicate the light brown apple moth (LBAM), a just-released report says the pest, present in New Zealand for 100 years, is controlled there by natural predators and that California should follow suit.
“LBAM is considered a minor pest that does not cause economically significant crop damage or have detrimental effect on native flora,” says the study, “Integrated Pest Management Practices for the Light Brown Apple Moth in New Zealand: Implications for California,” authored by Daniel Harder, executive director of the Arboretum at UC Santa Cruz, where he is adjunct professor in the Department of Ecology and Evolutionary Biology, and Jeff Rosendale, horticultural consultant in Watsonville.
“Natural predators keep LBAM in check, and it is so rare in the wild that it requires a true expert and meticulous searching to even find any sign of it,” says the report.
Harder and Rosendale spent three weeks in New Zealand in January carrying out the study, funded in part by the Arboretum and in part by Harder himself, Harder told the Daily Planet in an interview Friday.
The study recommends that the California Department of Food and Agriculture suspend plans for aerial spraying—slated to resume in June in the Santa Cruz and Monterey areas and to begin in August in Bay Area counties—and adopt Integrated Pest Management practices that begin with “monitoring to determine the extent to which LBAM populations are being parasitized or destroyed by predators.”
The CDFA says it can eradicate the LBAM in Northern California by using a pheromone–based spray called CheckMate, manufactured by Suterra in Bend, Ore. In nature, the pheromone is a scent released by female moths that attracts male moths. CheckMate uses a synthetic pheromone intended to confuse the male moths and disrupt reproduction.
In CheckMate, a synthetic pheromone and other ingredients are enclosed in microcapsules. After Checkmate was sprayed by air in Santa Cruz and Monterey counties in September—the first time the product has been sprayed over an urban population—more than 600 people reported adverse health impacts, leading to the growing condemnation among citizens and legislators of aggressive efforts to eradicate the LBAM.
Harder and Rosendale found in New Zealand the LBAMs are controlled in large part by natural predators and parasites, including birds, spiders, wasps, beetles, lacewings and earwigs. “Eighty to 90 percent of LBAM larvae are parasitized by natural predators before maturation,” the report says.
CDFA spokesperson Steve Lyle disputes the findings and conclusions in the report. Among them is the notion that California could depend on natural predators to control the moth.
“There are no natural predators in California,” Lyle said in a phone interview with the Planet on Friday. Because the moth is so recently arrived, predators have not developed, he said.
A key issue that impacts eradication plans is the question of how long the LBAM has been in California.
Lyle describes the arrival and spread of the LBAM in this way: In 2005 the CDFA set traps because they thought the moth might exist in California, but found none.
Then, in 2007, a single moth was found in a Berkeley backyard by a retired entomologist. After that, the CDFA once again set out traps and, this time, found an “infestation.”
“We didn’t detect the moth [earlier] because they weren’t there,” Lyle told the Planet.
Then, comparing 2005 to the time there were no moths, to the present number estimated as a function of those trapped, the CDFA concludes there is an infestation and that the moth is reproducing so quickly, emergency measures must be taken to stop it. When an emergency is declared the state is permitted to intervene before completing a report on the environmental impacts.
In an interview with the Planet, Harder referred to studies of James Carey, professor of entomology at UC Davis. Carey says the moth has likely been in California for decades.
Bio controls in New Zealand include native and introduced wasps and native tachinid flies. “The key to effective control with predators and parasites is to encourage a range of insects attacking all life stages,” the report says.
The “near-complete LBAM population suppression” by natural predators is encouraged by agricultural practices in New Zealand that include intercropping—cultivating two or more crops in the same space at the same time, the report says.
New Zealand officials set traps and monitor the number of moths they find. When the numbers grow beyond a certain threshold, they use insect growth regulators (IGR), insecticides derived from natural sources. (This is done in large part because the U.S has imposed the more aggressive treatment of the LBAM on exports destined to the U.S.)
The Harder report further says broadcasting pheromones by aerial spray will not eradicate the moth because males continue to find the females due to the wide dispersion of the synthetic pheromone.
Lyle responded: “Our TWG [Technical Working Group on the LBAM] thinks it is possible” to eradicate the moth using aerial spray.
“I’d be interested in seeing any hard data on it,” he added of the Harder report.
Further responding to the report, Lyle noted that the authors spoke to scientists at HortResearch, the New Zealand government agency that researches agricultural techniques, but failed to speak to Max Suckling, who works at HortResearch and is a New Zealand member of the Technical Working Group, which advises the U.S. and California agriculture departments on the LBAM.
In a further written response e-mailed to the Planet, Lyle quoted the TWG’s rationale for the spraying: The “pest threatens more than 2,000 different plants and, according to the USDA, has the potential to infest up to 80 percent of the continental U.S.”
Lyle further writes that comparing impacts on the environments of New Zealand and California “is like comparing apples and oranges.”
Lyle concludes: “CDFA’s mission and legislative mandate is to protect California from invasive species. The LBAM threatens the environment and our food supply. We developed our eradication program to respond to that threat and stand behind the sound science that is the foundation of the program.”
More information on the Internet:
Harder report and other anti-spray documents at www.stopthespray.org.
CDFA documents at www.cdfa.ca.gov/phpps/PDEP/lbam.
March 12, 1:30 p.m., state Capitol, room 4202 Sacramento, Assembly Agriculture Committee Hearing on LBAM
March 13, 1-3 p.m., Marin County Civic Center, 3501 Civic Center Dr., San Rafael, supervisors chambers
State Senate Committee on Environmental Safety oversight hearing: “The LBAM: Planned actions, alternatives and public concerns.”
April 7, 7 p.m., community meeting in El Sobrante: East Bay Waldorf School, 3800 Clark St.