Bee kind: Making greenhouse and nursery plants more pollinator-friendly

MSU entomologist David Smitley is working to provide the state’s greenhouse and nursery growers with tools to make their plants more pollinator-friendly and marketable without sacrificing pest management.

February 14, 2017 - Author: James Dau James Dau

David Smitley

In 2015, the two largest garden center chains in the country — Home Depot and Lowe’s — announced plans to phase out the use of a common and effective group of pesticides called neonicotinoids. The companies plan to eventually ban growers from using neonicotinoids on plants grown for sale in their stores. They also vowed to remove home garden products containing the chemicals from shelves within two to three years.

The announcement came after several years of public pressure from advocacy groups concerned that neonicotinoids had an adverse — and in some cases lethal — effect on already struggling honeybee and native bee populations. First registered for use in the mid-1990s, neonicotinoid pesticides are six chemicals absorbed through roots that provide plants with protection from a variety of insect pests that typically lasts two to three months. Though this has had undoubted benefits for pest management practices, it has also presented new threats to pollinators.

Neonicotinoids are systemic pesticides, meaning that they permeate every part of the plant, including nectar and pollen. Studies have shown that bees exposed to small quantities of neonicotinoid-infused nectar and pollen exhibit reduced energy and difficulties in flight and navigation. Though beneficial to pollinator health, the new neonicotinoid restrictions presented new challenges for greenhouse and nursery operations.

Michigan is No. 3 in the United States in greenhouse production and in the top 10 for number of plant nurseries. Michigan State University (MSU) AgBioResearch entomologist David Smitley is working to provide the state’s greenhouse and nursery growers with tools to make their plants more pollinator-friendly and marketable without sacrificing pest management.

“If you don’t have good pest management strategies, you risk losing your entire profit,” said Smitley, a professor in the MSU Department of Entomology. “With these new requirements, growers needed alternative methods and products, and they needed them quickly. It became something of a crisis for them, so we got involved right away.”

In September, Smitley and MSU AgBioResearch colleague Zachary Huang joined a team of scientists led by Rutgers University on a project funded by a $2.8 million grant from the U.S. Department of Agriculture’s National Institute for Food and Agriculture Specialty Crops Research Initiative (SCRI) aiming to address these issues. Smitley had actually been working on the subject earlier.

In 2014, MSU Extension educator Thomas Dudek alerted Smitley to the brewing neonicotinoid crisis facing Michigan greenhouse and nursery growers. Smitley responded by petitioning for an emergency grant from Project GREEEN, a joint research partnership between MSU, the Michigan Department of Agriculture and Rural Development and the state’s plant agriculture industries, to hold a series of workshops to educate growers about already available alternative means of pest control. These early efforts trained 23 growers representing nearly 10 million square feet and $3.5 million in plants in nine Michigan counties.

The current project aims to expand on these efforts by pioneering new means of pest control in the greenhouse, from alternative pesticides to biocontrols. The constraints of organic agriculture mean that farmers have few options for the kind of systemic protection offered by neonicotinoids. Smitley’s team will begin testing new products that they hope will be able to yield the same level of protection without harm to pollinators. Smitley said he believes biocontrols — predatory insects — offer particular hope.

“Using biological controls for pests in the greenhouse is complicated and requires a lot of knowledge to do it correctly,” Smitley said. “There are a lot of advantages to using them, however, that go beyond being neonicotinoid-free.”

One challenge of pesticide use is the development of resistance by targeted insects. Biocontrols are a way to circumvent this by relying on natural predators of the insects themselves. In the context of greenhouses and nurseries, this means releasing insect and mite predators at periodic intervals.

Currently, only about 5 to 10 percent of Michigan greenhouses and nurseries deploy biocontrols. In Ontario, 75 percent use biocontrols. In October, Smitley, Dudek and Wollaeger took 35 Michigan growers and industry representatives on a bus tour of Ontario greenhouses deploying biocontrols. Ten months later in a survey, those attendees reported they had changed their pest control practices to include biocontrols.

Next spring, Smitley will begin pesticide trials on top-selling annual and herbaceous perennial flowers, using 40 bumblebee colonies to evaluate the impact of systemic insecticides. The bees will be observed throughout the summer to assess the long-term impact of exposure. His team will also continue to conduct outreach, educating growers on the benefits of biocontrols and other alternatives to keep their plants marketable and pollinator-friendly.

“We want to be able to grow plants that will be safer for pollinators, both in the greenhouse and after planting,” Smitley said. “Biocontrols are the most sustainable long-term solution greenhouse growers are likely to see, and we want to help them adapt those methods into their management programs.”


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