Pest Management in Minnesota Agriculture

Insect pests have harmed harvests in Minnesota country since European immigrants first arrived in the area. Most local farmers, however, did not actively manage pests. Instead, they planned for the risk of losing some of their crop. It took both huge losses from the late 1800s grasshopper plagues and the industrialization of agriculture for Minnesota’s government to invest in pest management methods.

American Indians have farmed parts of southern present-day Minnesota for hundreds of years. Dakota women grew squash, beans, and corn to add to hunted meat and gathered foods. There are no written records of what, if any, insect pests damaged crops on Dakota farms.

In the early 1800s, European immigrants arrived and started farms that grew just enough food to take care of their families. These farmers thought insect pests were a punishment from God and that their damage was unpreventable. Due to this popular view, the study of insects, entomology, was more of a hobby than a job option. In 1823, Thomas Say was the first person in the state to study insects professionally.

The 1862 Homestead Act attracted new farmers to Minnesota. Due to the resulting increase in trade of crops, investors and governments started to calculate the cost of food damaged from insect pests. (At the third annual meeting of insect scientists in America, held in 1891 in Washington, D.C., Professor James Fletcher estimated that it amounted to $380,000.)

The Rocky Mountain Locust ruined many harvests across the Northern Plains in the 1800s. Minnesota was at the edge of the area in which the insects traveled. Parts of the state, including the Red River Valley, often lost harvests to the locusts. Between 1863 and 1878, the locusts came yearly and threatened thousands of farm communities with starvation.

In 1877, locusts destroyed 302,895 acres of wheat. In 1887, an outbreak in Otter Tail County was so bad that some farmers lost all their crops; some younger homesteaders left. In 1888, the governor of Minnesota, Andrew Ryan McGill, declared a state of emergency and sent aid to farmers. In the same year, the University of Minnesota created the Division of Entomology, headed by Professor Otto Lugger. Working within the College of Agriculture, its staff created and demonstrated insect management methods for the people of Minnesota.

In the 1890s, chinch bugs became a serious threat. Their numbers boomed as farmers planted more acres of wheat and corn. In 1895, the Minnesota Legislature granted $5,000 to state entomologists to destroy agricultural pests. Farmers used the money to spread a fungal disease among chinch bug populations.

In the early 1900s, management of pest insects on Minnesotan farms fell into two categories: natural and artificial. Natural methods included cleaning up dead plants from field perimeters, planting crops earlier or later, and planting varieties that withstood insects. The government paid a one-dollar bounty (worth about twenty dollars in 2017) for every bushel of grasshopper eggs collected.

Artificial pest management methods grew in popularity in the early twentieth century. Chemists created new toxins and products that could quickly kill insects. Many artificial control compounds contained ingredients that were also bad for people. Two of the main pesticides used, Paris Green and London Purple, contained the deadly poison arsenic.

Scientists and farmers began to understand that many crop problems and diseases were caused by insects. In 1912, the university’s Division of Entomology offered its first course on insects and plant disease. In the Twin Cities, scientists and mill owners knew that the pest they were dealing with was the Mediterranean flour moth, but they did not know how to stop it from ruining flour. They worked together to develop cleaning protocols that prevented the moths from laying eggs in machine parts and stores of flour.

In the early 1930s, droughts led to locust outbreaks across the Midwest—the worst seen since the 1880s. In 1932, Minnesota was the only state that provided financial support ($250,000) to control the locusts. Minnesotan researchers and farmers pioneered the use of insect surveys and weather forecasts to predict the number of infested acres and the amount of bait needed. Minnesota’s success in saving crops in 1932–1933 inspired national support for such programs.

During World War II, chemists created new chemicals for use in warfare and medicine. One such chemical, DDT, protected troops from mosquito-transmitted diseases such as malaria and typhus. After the war, farmers started using DDT to control agricultural pests. It was so effective that many farmers and researchers turned away from natural methods to focus on developing other effective chemical pesticides.

DDT is a broad-spectrum poison, meaning that it harms many different types of animals. In 1962, biologist Rachel Carson published Silent Spring, tracing the decline of many songbirds due to overuse of pesticides. DDT was the main problem, since farmers and mosquito control agents used it more than any other pesticide at the time.

In the 1970s, the public demanded more programs to protect the environment. This led most insect researchers to focus on creating and promoting integrated pest management (IPM) programs. These programs focused on managing rather than killing all pests in agriculture. They worked with farmers to determine acceptable levels of crop damage and to create systems of control. These ranged from farm management methods to biological control (using natural predators of pest insects) to chemical pesticides.

In 1995, U.S. farmers first planted a crop of potatoes that had been genetically engineered to produce Bt, a pesticide derived from bacteria. These new potatoes were unique because the pesticide was produced within the plant itself. Compared to other pesticides, Bt was relatively safe and effective. Scientists quickly added Bt traits to other crops that were vulnerable to butterfly larvae pests, including corn, cotton, and eggplant. By 2015, about 50 percent of the corn planted by Minnesota farmers contained Bt traits. Bt kills the corn root borer—one of the worst corn pests in the state.

In the twenty-first century, more and more farmers are interested in attracting insect predators to their farms. With enough of these “good” predators, they can keep pest insect populations below levels that cause harm to the crops. Researchers at the University of Minnesota work with farmers to figure out which predators (including some adult beetles, lacewing larvae, and syrphid larvae) kept pest levels low.

When a new pest comes to Minnesota, researchers look for its predators in its home state or country. The soybean aphid, native to areas in China, arrived in Minnesota in 2000 without its native predators. Before its arrival, soybean farmers in Minnesota did not have pest problems. In the 2010s, they apply pesticides in order to prevent up to 40 percent crop loss from aphid infestation.

Bees are important “good” insects in agriculture. Farmers could not produce strawberries, broccoli, pumpkins, or apples without their pollination of flowers. Between 2005 and 2015, researchers showed that honey bees and native bees are also harmed by pesticides. Although popular pesticides do not kill bees, they sometimes make it harder for them to find their hives.

In the 2010s, many bee hives have struggled to survive. Due to public concern, the Environmental Protection Agency implemented a new approval process that considers how “good” insects, like bees and some predators, respond to pesticides.