Across America’s Corn Belt, a battle has raged just beneath the surface of Earth for nearly 40 years.
Tiny white vermin infesting those first few rich inches have been chewing the roots off 13% of the nation’s largest crop every year, while farmers have been burying them under $1 billion worth of the best and latest biochemical weapons.
It has become an increasingly expensive war that the farmers cannot win.
“We can hope for control, a truce, but we will never get rid of the corn rootworm,” said Robert Metcalf, a professor of entomology and biology at the University of Illinois. “It was a mistake to think that we could.”
Effect of Pesticides
The irony, as Metcalf likes to point out, is that the beetle larva known as Diabrotica virgifera --the Western corn rootworm--was not a major agricultural pest until “we decided to make it one.”
“Pesticides--the indiscriminate use of pesticides--is what made the corn rootworm what it is today,” he said.
Between 1909 and 1948, the larvae crept from the sweet corn of Loveland, Colo., to fields abutting the Missouri River, spreading a little less than 12 miles a year. Then Nebraska decided to do something about it.
BHC, a soil insecticide applied before planting, blanketed Nebraska’s cornfields in 1949. In 1952, aldrin and chlordane were added; in 1954, hepatachlor.
By 1959, the rootworm had developed a resistance to all those pesticides and took to the road: Iowa, South Dakota and Missouri by 1962; Eau Claire, Wis., by 1964; northwestern Indiana by 1968.
Dominates Other Pests
Traveling at a rate of 68 to 116 miles per year, the resistant vermin conquered the Corn Belt by 1980 and today dominates all other corn root pests in most areas. Now farmers douse 40 million acres of corn every year with carbamates, organic phosphorus compounds and the few other pesticides that can still kill the rootworm.
“They’re sort of effective,” Metcalf said. “But we’re beginning to lose those as well.”
Pesticide resistance is an old concept that holds new danger. Recognized since the introduction of inorganic chemical toxins at the turn of the century, it was the sort of problem farmers and agriculture experts thought would be solved. Instead, it has just become worse.
The National Academy of Sciences estimated that there were only seven insect species resistant to at least some pesticide in 1938. But there were 25 by 1954, 224 by 1970, 364 by 1975, 428 by 1980 and as of 1984, at least 447.
Researchers say the growth in the number of resistant insects has slowed recently, but only because the world is running out of insects that are not resistant to something.
“Whereas the presence of resistance was a rare phenomenon during the early 1950s,” the academy said, “it is a fully susceptible population that is rare in the 1980s.”
But more important than the total number of somewhat resistant insects are those pests that are virtually immune to everything, “monster bugs” as Metcalf calls them. More than a dozen important insects are now resistant to all five major classes of insecticides. Among them are the housefly, the Colorado potato beetle, the green peach aphid, the diamondback moth, and, of course, the German cockroach, the type most familiar to householders.
Experts only expect the problem to get worse unless some fundamental changes are made in how pests are controlled.
“Twenty years down the road,” said Allan Felsot, economic entomologist with the Illinois Natural History Survey, “unless new types of pesticides are developed and we learn to use them properly, all the chemicals we have now likely won’t work anymore--at all.”
Entomologists joke about it--"any pesticide will work on the common household cockroach if you apply it with the bottom of your shoe"--but they recognize that the problem is exacting a high penalty.
In a purely economic sense, it has become extraordinarily expensive to develop a pesticide that will work: $45 million in 1986, contrasted with about $1 million in the 1950s. Researchers have to test an average of 22,000 different formulas before they find one the target pest does not already resist; in 1952, the number was 1,200.
These costs are reflected in the price of the pesticide to the farmer, and subsequently in prices to the consumer. And the farmer is getting less and less for his money. The sad fact is that the percentage of crop yield lost to pests has risen since 1900 for nearly every major crop except apples.
Health Threat Feared
There are also human costs. Although no one reasonably expects pesticides to be completely harmless--they are intended to kill something, after all--scientists and public officials have become concerned that many pesticides may pose a serious health threat to farmers or people living in the surrounding communities.
The federal Centers for Disease Control published a study last fall linking frequent use of a popular herbicide with soft-tissue cancers among Kansas farmers. A more recent preliminary survey in Nebraska found a dramatic increase in communities where nitrate-based fertilizers had contaminated ground water.
The researchers say they do not know yet whether it is the fertilizer or something associated with its use--an insecticide, perhaps--that is responsible for the cancers.
Findings like these have prompted great public concern about the use of pesticides, and some governmental action. The Environmental Protection Agency has about a dozen pesticides under special review, and the proposed Federal Insecticide, Fungicide and Rodenticide Act, which was defeated in the last Congress but is expected to be reintroduced, is intended to accelerate this review process.
The actions, if successful, may make the use of pesticides less risky for farmers and the public, but they will not kill any more bugs. Current laws have already made it more difficult to develop new products.
“In order to put a product in the environment today and get EPA approval, you wouldn’t believe the amount of tests you have to do,” said Jack Early, president of the National Agricultural Chemicals Assn. “I’m not saying they shouldn’t be done, but they are making it harder to put out a profitable product.”
Although legalities dilute pesticide use, some necessary environmental constraints dilute the products directly. The need for pesticides to be biodegradable has created yet another problem for the Corn Belt. In many areas, soil organisms have developed a way to use the pesticides for food, eating the farmers’ weapons before they can even get to the enemy.
Metcalf shook his head. “It’s difficult to see how anyone can remain intelligently optimistic about the future of chemical control,” he said. “The outlook is dismal and getting worse.”
Other experts are not quite so pessimistic. David McNeal, a pest management program leader with the U.S. Department of Agriculture, said, “My sense is that we’re not really losing ground fast, if at all. But yes, it’s a problem, and yes, I’m concerned.”
The corn rootworm’s migration, although illustrative, pales in comparison to some of the great insecticide “ecocatastrophes.”
Metcalf sat in his entomology lab and ticked off examples, moving from the fingers of one hand to the other and then back again.
“The Colorado potato beetle out on Long Island (N.Y.) is now nearly indestructible. They’ve thrown 15 pesticides at it since 1950 and they really don’t know what to do.”
“Look,” he said, referring to a chart from a 1986 book chapter he wrote on the subject. “They started with DDT in 1945; that lasted longest, seven years. And the rest. . . .”
The rest read like short obituaries: Dieldrin 1954-1957; Endrin 1957-1960; Carbaryl 1959-1963; Monocrotophos 1973-1973; Phosmet 1973-1973; Phorate 1973-1974.
Nothing has lasted more than two years since, and a last-ditch effort to use an insecticide called aldicarb a few years ago has badly contaminated well water in the region.
Problems With All
“To some extent,” he said, “all pests pose a resistance problem eventually.”
The reason is clearly spelled out in most high school biology texts. As Rachel Carson wrote in her influential 1962 book “Silent Spring”:
“Darwin himself could scarcely have found a better example of the operation of natural selection than is provided by the way the mechanism of resistance operates.”
Put simply, if a farmer sprays or lays enough of a pesticide on fields, it will kill all of the insects susceptible to it. But it will not kill all of the insects, and those that survive--"the fittest"--do so because of some chance variation in their genetic makeup. Insects have a lot of these chance variations.
“Insects are among the oldest inhabitants of the Earth,” Metcalf explained. “They go back 300 million years, and they’ve had an enormous opportunity to develop a varied genetic makeup.
“They’ve got all kinds of genes, and so the more we select, the more kinds of resistance we build into them, and the worse the gene pool gets.”
New Generation in Weeks
The farmer thus unwittingly pushes the pest into a Nietzchean niche--that which does not kill them makes them stronger. The more pesticide the farmer uses, the more “selection pressure” is put on the insect, and the more chance resistance gets passed to future generations. And each increasingly resistant future generation is only a few weeks away.
“What we have done is, we have created these races of monster bugs which nothing can kill,” Metcalf said.
Ironically, the insecticides do appear to be effective at doing one thing: killing the natural enemies of the pests in question. In the late 1950s, cotton farmers in Louisiana and Mississippi tried to eradicate the cotton bollworm with various organic phosphates and chlorines. The bollworms snapped back by the 1960s, but everything that used to eat them had been wiped out.
Better Off Before
The final irony is that farmers were slightly better off before it was determined that pests were a problem that could be solved with chemical control.
“It was mainly the terrible enthusiasm as a result of the introduction of DDT in World War II, when it worked so well on mosquitoes, flies and lice and averted a number of disease epidemics,” Metcalf said. “People seriously speculated we wouldn’t need any entomologists anymore, that we were going to spray everything with DDT and it was all going to be very simple.”
Metcalf even remembers a Reader’s Digest article proclaiming, “You can count the flies in Iowa on only one hand.”
But DDT was not a panacea and turned out to be a poison as well. By the time the chemical started to be phased out in the late 1960s, it did not work anyway.
For a problem so serious, and so entrenched, the solution is deceptively simple: Use fewer pesticides; use them judiciously, and let nature take care of the rest.
This notion, known as Integrated Pest Management, is not new.
“IPM as a concept really goes back to the ‘20s or ‘30s,” said McNeal, who heads the USDA’s IPM program. “There were some very visionary entomologists who saw we were going to have this problem.”
Several elements are necessary for effective Integrated Pest Management, but most conform to the idea that farmers need to work with nature rather than against it. With the help of natural pest control, farmers theoretically can get by with less pesticide and thus be less likely to add to genetic selection pressure on the pest.
For example, corn farmers with a rootworm problem can practically eliminate it by rotating crops. If they fail to plant corn in an infested field for one season, the vermin will starve.
Or, in other crops, farmers may be able to gain the upper hand by allying themselves with a natural predator to the pest, either by eliminating pesticides that kill it or, in some cases, reintroducing it.
“My humble example is that a hungry ladybug beetle can’t tell the difference between a resistant aphid to DDT and a non-resistant one,” said Metcalf. “It’s going to eat them all.”
As explained by the USDA and others, IPM makes so much sense that it is a wonder that every farmer has not embraced it as a way of life. Some have and with great success: Mississippi cotton farmers have been able to save $15 million a year in pesticide costs using IPM; corn growers in Clark County, Wis., saved $13,000 on insecticides; raspberry growers in Washington state avoided $400,000 in losses and saved $24,000 in chemicals.
But these are, by and large, examples and not trends.
‘Saving Them Money’
“Some farmers have been (using IPM) for a long time really, and the main reason they’re doing that is that it’s saving them money,” said Don Rollins, director of the Natural and Environmental Resources Division of the American Farm Bureau. “But there’s a lot more that needs to be done.”
Rollins said part of the reason that more farmers are not using IPM is that it has only been promoted seriously for about 10 years and “you can’t just usurp your whole way of doing things overnight.”
Felsot, of the Illinois Natural History Survey, who spends several days a year lecturing groups of farmers on the principles of IPM, said a big part of the slow acceptance of the method is psychological. He calls it the “macho yield problem.”
“A lot of times farmers use a lot of pesticides because they think it will increase their yield, which it will, but maybe not as much as what they had to spend to get it,” he said. “So they go around bragging they had this and that yield, but they won’t tell you how much they made on their corn.”
Felsot and others point out that macho yield is also reinforced by salesmen from chemical companies, who tend to push their products to the exclusion of other practices. In central Illinois, this powerful message is also implied in the approximately 40 hours of television advertising for agricultural chemicals that farmers see between the September harvest and May planting.
But Early, of the National Agricultural Chemicals Assn., said that his association is a strong advocate of IPM and that he believes that most chemical companies are responsible about how they present their products.
“I’m sure some salesmen do give a hard sell,” he said. “But I would hope that the farmer would have an interest in the area and consult with others before making any sort of decision.”
McNeal concurred. “There’s nobody holding a gun to the farmer’s head saying, ‘You have to use this pesticide,’ ” he said. “Farmers have to be educated consumers.”
Whether farmers will do so remains to be seen, but most seem to agree that the depressed farm economy can only help. As one corn grower, who did not wish to be identified, said, “I spend a lot of money on this. If somebody’s got a way where I don’t have to, I’ll listen.”
It should be pointed out that a technological innovation may change the pest management picture considerably. Researchers are experimenting with ways to change crop plants genetically so they will become more resistant to pests, circumventing the need for pesticides and perhaps effectively controlling the insect.
Experts cautioned that this sort of plant engineering is more than a decade from the average farm, however, and one can sense their reluctance to ascribe too much promise to another new technology.
“It’s not the technology, it’s how we use the technology,” Felsot said.