Scientists Highlight More Green Alternatives to Pesticides

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.

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