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When Chris Schlegel started working at DS Cole, one of the largest commercial greenhouses in New Hampshire, the pest control strategy was simple: Once the first sign of insect damage was spotted, spray everything with insecticide, and repeat every week.

Chris Schlegel, head grower at DS Cole in Loudon, says that biocontrols have since displaced chemical insecticides as their first line of defense against pests.

That strategy has since been shelved in favor of another approach, which has Schlegel and her co-workers reaching for chemical controls less often and using less of them when they do. Instead of insecticides, they primarily use what are known as “biocontrols,” tools which leverage nature’s processes to keep insect damage at bay.

In the greenhouse industry, biocontrols largely take the form of predatory insects which are harmless except for their prey. Many growers, such as DS Cole, have adopted biocontrols as a way to greatly reduce their use of insecticides.

Like any new technology, there have been early adopters, but there’s still a lot of growers in New Hampshire who rely on pesticides as their sole means of pest control. Jonathan Ebba, a field specialist with UNH Extension, and his colleagues — including Amber Vinchesi-Vahl and Amy Papineau — are working to make the transition to biocontrols easier and more successful. 

“As I’m doing direct technical assistance with greenhouse growers in the state, I’ve begun to see that they needed clear, step-by-step directions,” says Ebba, who is part of the team that helps growers such as DS Cole. “So I put together a biocontrol starter pack. This is a recipe that folks can use to get started, and in subsequent years can adapt it to suit their specific needs.”

The biocontrol starter pack includes information about the specific organisms available to growers, as well as a proscribed strategy for how to deploy them in response to the appearance of pests. Ebba’s plan calls for growers to regularly monitor the activity of insects in their greenhouse — such as through the use of sticky yellow cards that catch flies as they move between plants — and when they should respond by releasing predatory insects.

Chemical pesticides will likely still be necessary, though their use will be diminished, both in frequency and in volume.

“I don’t know anyone who’s growing ornamentals without pesticides,” Ebba says, “but the biocontrols greatly reduce the amount that they have to use.”

At DS Cole, Schlegel began experimenting with biocontrols in 2008, by releasing mites that prey on the thrips that were damaging their gerbera plants. Those thrips had developed resistance to chemical pesticides and multiple sprayings per week couldn’t control them. Soon the experiment expanded to include controls for the white flies that were damaging their poinsettia crop. In subsequent years, DS Cole started growing potted herbs, and the presence of edible plants made the reduction in pesticide use even more important.

Now, Schlegel says, biocontrols are the operation’s first line of defense against pests, with chemical controls used only in cases of pest outbreaks that don’t yet have a commercially available predator.

Benefits of biocontrols are broad, Schlegel says. First and most importantly, it’s safer for the greenhouse’s 80 employees and their surrounding environment. There are other benefits, too, as many of the plants that DS Cole grows are bought by other growers who don’t want plants treated with pesticides to disrupt their own biocontrol strategy. Lastly, since they’ve reduced their use of insecticides, they’ve started to notice on their yellow sticky cards native insects, volunteer biocontrol agents that flew in through open windows but wouldn’t have survived in the days of widespread chemical use.  

How about cost — is DS Cole spending more on biocontrols than they would if they had stuck to conventional sprays? Schlegel doesn’t see the point in crunching the numbers.

Chris Schlegel, head grower at DS Cole in Loudon, says that these sticky, yellow cards are placed throughout the greenhouse and are used to monitor for the presence of unwanted insects.

“I think the bottom line for us and a lot of other growers now is the consideration of the environment and the safety of employees, the consideration of the honeybees and all that, makes it worth it,” Schlegel says. “It’s been really successful. We do still get insect pests, but we can target and control. It’s so much easier to control with chemicals if you haven’t been using a lot because there isn’t that resistance.”

Extension has been a steadfast partner as DS Cole expanded its use of biocontrols, Schlegel says. Integrated pest management specialists have been available to help with pest identification and control strategies, and have organized monthly IPM webinars or in-person workshops. DS Cole agreed to host one such workshop in October 2025.

“We get a lot of help from UNH, and they partner with many people who are really knowledgeable too,” Schlegel says.

“One of my goals is to be able to report a reduced volume of pesticides that are being utilized for New Hampshire’s ornamental crop as a result of biocontrols,” Ebba says.

A future where New Hampshire greenhouses routinely look to biocontrols before pesticides is one in which the businesses produce healthier products and have safer employees – and one in which the surrounding environments are likely to benefit, too.