California Deploys Wasps, Scientists Highlight More Green Alternatives To Pesticides
The 15 million wasp eggs scattered across neighborhoods in Sacramento and San Luis Obispo counties represent a rare return to historical methods of pest control.
Deployed last week, the eggs will soon give rise to tiny wasps (Trichogramma platneri), each no larger than a grain of rice. The stingerless species is naturally inclined to lay its eggs inside light brown apple moths' own eggs. Scientists hope the natural weaponry -- also soon to be deployed in San Mateo and San Joaquin counties -- will purge the pest's progeny and help stave off the need to launch a chemical attack to protect California's crops.
Despite the implementation of this alternative strategy for fighting agricultural pests, and a new broad pest management plan in the works for California, the aerial spraying of pesticides continues to dominate the field. An estimated one billion pounds of pesticides are applied to U.S. farms, forests, lawns and golf courses each year, despite the promise of alternative strategies, such as introducing predatory species or enhancing biodiversity in and around crops. The trend also continues in the face of mounting concerns over the potential risks posed by these chemicals -- with diabetes and poor prenatal brain development recently added to the list.
Monsanto, a U.S.-based agricultural organization, remains under the gun after a report suggested that industry regulators had known for decades that its Roundup weedkiller could cause birth defects.
"If we were to show that we could cut pesticide use to zero, there are a lot of [big business] people that would not be happy," said Miguel Altieri, an expert in agriculture and ecology at the University of California, Berkeley.
A quick Google Earth flyover of California's Central Valley -- around Lodi, Modesto and south to Fresno -- provides a good view of what high input of pesticides can look like. The major agricultural hub typically bears a low diversity of crops, large fields and few natural areas, said Claudio Gratton, an entomologist at the University of Wisconsin, Madison.
But it hasn't always been that way.
In the late 1800s, the cottony cushion scale decimated the state's citrus industry after the pest's unintentional importation with citrus trees from Australia. There were no natural predators nearby. So, entomologists returned to Australia in search of an insect that would prey on the scale. Intentional introductions can be disastrous -- often wrecking havoc on an ecosystem -- but a shipment of Vedalia beetles proved successful, and they remain a mainstay in citrus farm management.
In more recent decades, California farmers and vintners have added strips of alfalfa to cotton fields and blackberries around plots of grapes in an effort to provide a habitat for beneficial insects.
But the widespread introduction of "magic bullets," such as genetically modified crops and pesticides, slowly eroded interest, suggested Altieri. It became a lot easier to simply spray chemicals. And the subsequent growth of large monocultures, pesticide resistance, secondary pest outbreaks and pressure from big corporations and pest control advisers, he added, has further hooked farmers on the chemicals.
Meanwhile, new research continues to validate the wisdom of pre-chemical farmers, who generally tended to smaller plots and preserved more natural lands.
A study by Gratton and his Wisconsin colleagues across a seven-state region of the Midwest, published online Monday in the Proceedings of the National Academy of Sciences, found that landscape simplification -- the introduction and enlargement of monocultures or the shrinking of edges between farmland and natural habitat, for example -- was associated with insecticide application over an additional 5,400 square miles of land, an area the size of Connecticut.
In effect, larger crop fields and smaller natural lands makes "it easier for pests to make a living, and makes living harder for their natural predators," Gratton said. "Farmers respond by spraying increased amounts of pesticides."
The researchers also concluded that farmers still derive substantially more income from the additional cropland than they pay out for the pesticides: an estimated total of $26 billion versus $69 million across the Midwest in 2007.
Of course, that comparison only accounts for direct costs of the pesticides. A study in 2009 suggested that dependence on pesticides in the U.S. results in about $12 billion in environmental and societal damages, due to indirect costs such as crop losses and ground water contamination.
"If you continue doing these kinds of studies, and stack up all of these values like public health, then all of the sudden you have something that is a lot more significant to society than just looking at income derived from the land," said Gratton.
Further, as he noted, the choice for farmers is not all or nothing. Farmers can be strategic in placing patches of natural areas, even using perennial biofuel crops, such as switch grass, to attract natural predators.
"There are marginal lands such as low-lying wetlands and slopes that are very poor for producing food crops but are otherwise good for things like grasses and trees," he said. "This not only would potentially lower pesticide use, but also decrease runoff into streams, improve biodiversity and lower greenhouse gases."
Both Gratton and Altieri agreed that incorporating more diverse landscapes would also help California in its wasp-moth battle.
It would provide the wasps with greater habitat so that they could "stay, reproduce and expand," said Altieri.
Steve Lyle, director of public affairs for the California Department of Food and Agriculture (CDFA), noted that the state does look to a large pool of tricks to outwit pests.
"For decades, the department has been committed to integrated pest management. We choose softest approach possible first; pesticides are a last resort," he said.
Lyle highlighted examples, including the removal of fruit from grape vines to deter the devastating European grapevine moth and a long-running program to sterilize and release male metflies.
Changes to land use, such as preserving natural lands around a crop field, however, fall outside of his department's jurisdiction.
The CDFA has begun developing a broad new strategy in its war on agricultural pests. The environmental impact report will assess the effects of a number of pests that scientists believe could be detected in the state, and then evaluate a range of options to manage and control the pests.
The department will be accepting public input from stakeholders, private citizens oand environmental groups on the proposal until July 25. The final two of five public meetings will be held this week: Tuesday night at the San Francisco public library from 5:30 p.m. to 7:30 p.m., and at the same time Wednesday at the University of California, Fresno, Business Center.
However, the efforts are not enough, said Altieri, pointing out that only a tiny fraction of the funds for agricultural research in the University of California system go toward "low input approaches."
Altieri has helped lead a grassroots effort to spread interest in natural methods of pest control. The farmer-to-farmer program allows farmers to teach and observe one another implementing various strategies.
While the alternative tactics may not provide the same kind of instant gratification that can come from applying pesticides, not only will they result in a reduction of pests over time, Altieri suggested, but they will also prompt a return of pollinators and birds, enhance soil fertility and diminish soil erosion. In other words: a healthier ecosystem.
"Why do we always blame the pests? In order to have a pest, you have to have a system that is unhealthy," said Altieri. "Monocultures are the worst systems you can have. They invite pests. But you can increase immunity through diversification."
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First Posted: 07/13/11 03:48 PM ET Updated: 09/12/11 06:12 AM ET