The discovery of two citrus pests captured on sticky paper has prompted the state to call for mandated insecticide spraying of citrus trees near the Santa Maria Public Library. The insecticide treatment being used, however, has local beekeepers worried.
The pest—the Asian citrus psyllid—could carry a disease known as citrus greening, which is deadly to citrus trees, has no cure, and has the potential to knock California citrus production down by at least 20 percent. Psyllids were detected at two different residential sites near the Santa Maria Public Library in January, and the California Department of Food and Agriculture (CDFA) started preventative measures on Feb. 28.
Two insecticides are being applied to every citrus tree within an 800-meter radius of the residences where the pest was initially found. One of the pesticides is applied to the leaves, and the other is applied to the soil for the roots to soak up.
Santa Barbara County Assistant Agricultural Commissioner Guy Tingos said there have been many studies on the best way to control the pest and prevent spread of the disease. Many of those studies took place in Florida, where the disease has contributed to cutting commercial citrus production by 40 percent since 2001.
“A lot of information seems to say that this [dual insecticide treatment] is the most effective way to treat the insect,” Tingos said.
The CDFA has treated for the pest in residential areas using the two-pronged treatment since the first California sighting in San Diego in 2008. Since then, sticky paper has hung near residential and commercial citrus trees in most California counties as a way of spotting the pest. Residents are given a 48-hour notice before spraying begins.
The insecticide being applied to the roots of the trees is what has Santa Maria beekeepers concerned about the future health of their hives.
It’s called Merit, and what has beekeepers worried is the pesticide’s active ingredient, imidacloprid.
The insecticide combats a wide variety of pests and is used worldwide to treat lawns, roses, genetically modified seeds, and crops. It’s a neonicotinoid—a synthetic insecticide chemically related to nicotine—and attacks pests by causing nervous system problems that eventually lead to their deaths.
Merit’s label warns applicators not to apply the insecticide while the affected plant is in bloom because it’s “highly toxic to bees exposed to direct treatment or residues on blooming crops or weeds.”
While Merit isn’t the insecticide being applied directly to citrus tree leaves, and the trees aren’t in bloom yet, Santa Maria Valley Beekeepers Association President Ronald Gromak said beekeepers are concerned about the residual effects.
“Because of the long-term effects of this ground spray, our bees will be affected by this forever,” Gromak said. “It comes out in everything … it comes out in the pollen, it comes out in the fruit.”
An insecticide applied to the roots or soil at the base of a citrus tree is absorbed into the plant over time. The insecticide works from the inside out and eventually becomes part of the tree’s leaves, branches, and fruit. As Asian citrus psyllids eat the leaves, they also absorb the pesticide and eventually die off.
According to the CDFA, imidacloprid isn’t toxic to humans and was introduced to the United States in 1994. The insecticide became widely used in commercial agriculture starting in the early 2000s.
CDFA Director of Public Affairs Steve Lyle said that if the Asian citrus psyllid makes its way into commercial orchards, imidacloprid will be the insecticide most growers would use to combat the pest.
“If the psyllid infestation gets worse, the use of imidacloprid could increase,” Lyle said. “We have an invasive species that we’re dealing with that is threatening the citrus industry in California.”
Lyle added that the state’s two-insecticide approach has so far been successful in preventing the pests and citrus greening disease from reaching commercial citrus orchards. Lyle also said they were aware of the concerns of Santa Maria beekeepers and were interested in learning more.
Santa Maria-area beekeeper Mike Pender said he’s had up-close-and-personal experiences with imidacloprid. Pender, a beekeeper with 15 to 20 years of experience, said he lost his whole population of bees four years in a row—and he attributed their deaths to exposure to the insecticide.
“I had all my wax and stuff tested through a private company and they said I had imidacloprid,” he said. “Never in my life had I lost all my bees like that … every last bee I had.”
His problem matches a phenomenon that scientists dubbed colony collapse disorder (CCD). Symptoms of the disorder are the loss of a hive’s bees; the insects leave home and don’t make it back.
Since the early 2000s, beekeepers worldwide have been affected by the disorder. It’s estimated that the problem has caused a loss of 50 percent of the world’s honeybee population. Colony collapse is blamed for the struggle Central California’s almond growers are having this year; there aren’t enough bees to pollinate more than 200,000 acres of waiting trees.
Many scientists say the disorder is caused by a number of things, such as funguses, insecticides, environmental changes, cell phone usage, disease, and parasites. Some scientists in Europe have linked the disorder to neonicotinoids like imidacloprid and, for that reason, the insecticide has been banned in many European countries.
The Harvard School of Public Health released the results of a study in March 2012 that pointed to imidacloprid as a culprit behind colony collapse. The study used 16 hives, dosing them with varying levels of the insecticide for 13 weeks.
None of the hives exhibited any symptoms after 12 weeks, but 15 of the 16 hives were dead 23 weeks after the imidacloprid dosing.
“Dead hives were remarkably empty except for stores of food and some pollen left, a resemblance of CCD,” the study said. “Data from this in situ study provide convincing evidence that exposure to sub-lethal levels of imidacloprid cause honeybees to exhibit symptoms consistent to CCD months after imidacloprid exposure.”
Sub-lethal doses are below 20 parts per billion of the insecticide. The Sun contacted the maker of Merit, Bayer, for a response to the study, but the company hadn’t replied to the Sun as of press time.
The findings of the study are consistent with how Pender describes the loss of his bees. He said the symptoms aren’t noticeable until sometime in November, months after the bees have used their buzzing ways to pollinate agricultural fields and make their honey.
Although Pender keeps bees to make honey, he no longer has bees for commercial use in agricultural fields because he’s lost them too many times.
“People think it’s alright, but it’s not, this is our environment,” Pender said. “It’s all interconnected, and these people don’t get it.”
Contact Staff Writer Camillia Lanham at clanham@santamariasun.com.
This article appears in Mar 7-14, 2013.
