Pesticides used on corn and soybeans can harm beneficial insects, especially pollinators like bees. A team of researchers at the University of Nebraska-Lincoln is looking at how landscape design, including the use of windbreaks, can help limit pesticide drift around pollinator habitat.
If you’ve been paying attention to the concern about bees, you’ve likely heard of neonicotinoids. They’re considered a big contributing factor in declining bee populations. Neonicotinoids is actually a class of insecticides, said Judy Wu-Smart, assistant professor and extension specialist in pollinator health at the University of Nebraska-Lincoln.
“They are different from older classes of chemicals because they have a systemic action to them. So they target the central nervous system of insects, particularly,” Wu-Smart said. “Systemic” means these highly toxic chemicals move throughout the whole plant—good for farmers, bad for bees.
“So they're useful in agricultural production because they can protect plants from root damaging insects and pests, where spray applications may not reach them,” Wu-Smart said. “But they're concerning for pollinators because bees that are foraging on plants that have been contaminated with neonicotinoids can be getting it directly through nectar and pollen.”
Corn and soybeans don’t need to be pollinated by insects. But most commercial corn and soybean seeds now have a pesticide coating, and Wu-Smart said those chemicals can travel to plants bees rely on, like those that grow along roadsides or in field corners.
“The seed treatments on the seeds themselves can come off of those corn seeds and the dust or the talc that is used in the equipment to lubricate those seeds tend to have very high levels of this neonicotinoid residues. And when planting occurs, the dust can come off of the fields and blow into habitat and flowering weeds and trees that bees would be visiting,” Wu-Smart said.
Neonicotinoids can have a variety of different developmental and behavioral effects on non-target insects like bees and butterflies, Wu-Smart said, and also make them more susceptible to other diseases.
“Chronic effects that can inhibit foraging, learning, memory, cognitive functions that really inhibit the colony from developing well. They can have effects on the queen's ability to lay eggs and produce brood,” Wu-Smart said.
So, Wu-Smart and others are studying how agricultural landscapes could be designed to limit or prevent pesticide drift and provide protected pollinator habitat. Gary Bentrup is a research landscape planner for the US Forest Service at the USDA National Agroforestry Center in Lincoln. He’s looking into the role of windbreaks—rows of trees planted along fields. He says the basic idea is that a row of non-pollinator friendly plants, like evergreen trees, can act as a shield between crops treated with neonicotinoids and pollinator friendly plants on the other side.
“Evergreens are generally a good choice for that, their fine leaves and branching structures are effective at trapping pesticide drift. And they generally don't have resources that are of interest to pollinators. So spruces are particularly good choice, Colorado spruce, Black Hills spruce and Norway spruce,” Bentrup said.
In addition to trapping pesticides in the air, the roots of the trees can help filter pesticides in the soil.
“And in particular, we're concerned about early flowering plants because that's the time when corn's being planted, and so species that are flowering during that time period might be actually more of a sink for this pesticide,” Bentrup said.
Wu-Smart, Bentrup and others are conducting their research at the university’s extension center near Mead, which has established windbreaks and corn and soybean fields. They’ll test pesticide contamination in the air, as well as the nectar and pollen of plants bees are foraging on. Bentrup said the research will help them figure out ways to use existing windbreaks as well as how future plantings could benefit pollinator habitat.
Bentrup said many farmers understand the importance of pollinators for food security. “And as a general rule, I find that edge of field practices, kind of like what we're suggesting, are usually more palatable than changing an operation in the field,” he said.