MADISON — Months after a whitefly infestation forced tomato grower Backyard Farms to cease operations and furlough employees, the landmark company is reintroducing the ripe red fruit to stores around the northeast and eyeing new methods of warding off destructive pests.

The farm, which produces about 27 million pounds of tomatoes a year, is back in operation and its 200 employees placed on furlough during the recent shutdown have returned to work, according to officials at a celebration of the new crop on Wednesday.

“We’re here today to celebrate the re-opening of our facilities. It hasn’t been an easy time for us these past few months and we know it hasn’t been easy for our customers either,” said Paul Mucci, president and chief operating officer of Backyard Farms. “I want to thank our employees for their patience and professionalism during the last six months.”

The greenhouse, one of the area’s largest employers, temporarily closed in July because of a whitefly infestation while the 42-acre farm was cleaned out. Whiteflies are small insects that feed on leaves, and while they pose no risk to humans they suck away plant juices, causing leaves to yellow or die.

The company is not disclosing how much revenue was lost during the shutdown, although almost a half-million plants were destroyed, said company spokesman Mike Aalto.

On Wednesday, plump red tomatoes hung from vines while employees got back to work. The tomatoes have been back in stores including Hannaford, Whole Foods, Walmart and Shaw’s since mid-December, said Aalto.

During the shutdown, all 200 of the company’s employees were furloughed and given the option to complete up to three weeks of community service while remaining on company payroll.

“This is a very important occasion not just for Madison, but for the state,” said Gov. Paul LePage, who attended Wednesday’s celebration and toured the greenhouse. “Backyard Farms is a major employer, as well as an innovative and interesting business that inspires people who come to Maine.”

Employees said they were happy to be back at work, although the furlough provided unique opportunities.

“I think it’s difficult for anyone at any company to be in that situation,” said Liza Graham, 30, of Solon, a picking and packing manager who returned to work the first week in December.

“Production so far has been excellent. The quality has been outstanding,” said Ken Downey, of Cornville, who is also a picking and packing manager. He has worked at Backyard Farms for about four years and said he appreciated that the company and the state Department of Labor worked together to make sure jobs would back.

“I had a list of stuff I was going to do at home, but once I finished it I was chomping at the bit waiting to get back to work,” said Downey.

In the future, the company will be doing a number of things to better manage pests, including better crop management and prevention tactics such as increased use of beneficial insects that eat destructive ones in greenhouses, which operate as mini-ecosystem in many ways.

One expert in the field said biological controls such as other predatory insects can be especially effective against whiteflies.

“In a greenhouse, you can get a severe population rapidly, primarily because of the environment. You have a mini-Florida,” said Jim Walgenbach, an extension entomologist at North Carolina State University.

Walgenbach, who specializes in tomato plants, said biological controls are usually optimal in any kind of agriculture setting, from backyard gardeners to large-scale agriculture businesses.

One reason farmers often use biological controls to kill whiteflies is that their short lifespan allows them to evolve quickly enough to become increasingly insecticide resistant, he said.

Biological controls, while not always eliminating every whitefly, are also good against the insects because their small populations don’t harm the host plants — in this case, tomatoes. The method can prevent an existing population from getting out of hand without affecting the yield or the quality, Walgenbach said.

Inside the two large greenhouses that make up the Madison farm, ceilings almost 30 feet high allow for stable temperatures of around 75 degrees year-round, said Erika Verrier, manager of integrated pest management, during a tour on Wednesday.

In addition to nearly 500,000 tomato plants, the greenhouses are home to more than 1 million insects, including 40,000 bumblebees whose job it is to pollinate the plants.

Basic crop care is one of the most critical components of preventing future infestations of pests and disease, said Verrier. The plants, which are supported on a wire, must be moved weekly to ensure that they grow straight up. Leaves are pruned to create even spacing between plants and ensure consistent quality of each tomato, she said.

Another task done on a regular basis is the pruning of flowers, which helps the bees pollinate. Backyard Farms produces four varieties of tomatoes and depending on the variety, the number of flowers the plant produces can vary, said Verrier. But all plants can benefit from the pruning of flowers, which ensures that each tomato can reach its optimum size and ripeness, she said.

Leaves are also removed— up to three leaves per plant per week— to keep the weight of the plant balanced on the vine and expose the fruit to adequate sunlight. Walking through the greenhouses, the plants are organized in rows assigned to personal gardeners, who tend to the same plants day after day. This gives employees a sense of responsibility for their plants and also makes it easier to identify a problem when it arises, said Verrier.

To assist with pest control, the greenhouse has placed a sticky yellow tape throughout every row of plants to catch whiteflies and other flying insects, said Verrier. The tape has been used in the past, but will now stay up permanently for prevention purposes rather than control of isolated areas of the crop, she said.

In the newly reopened greenhouse, biological controls will also play a greater role in pest control, said Verrier. About 1 million beneficial insects per week are being introduced in the greenhouse, which is more than had previously been used. They include parasitic wasps and predatory insects. Pest control is also expanding the types of beneficial organisms that are used, including a beneficial fungus beauearia beassiana that can live on plants to infect pests when they are in the larvae stage of life and about 2,000 new Mullien plants, a large leafy plant where beneficial insects can live such as the dicyphus hesperus, which eat between 30 and 40 whiteflies per day.

The plants are moved around the greenhouse so they can seek out and eat white flies, said Verrier.

Whiteflies, though their population is low right low, can still be found in the greenhouse and they will likely never be eradicated, said Verrier. The insects are an inevitable part of the greenhouse ecosystem, but in the future their numbers will need to be better maintained, she said.

“In order for wasps and predatory insects to thrive they need a food source,” Verrier said. “It’s always good to have some whiteflies so you can build up a beneficial population. It’s really about numbers, you need to continuously be outnumbering your pests.”

Morning Sentinel staff writer Matt Hongoltz-Hetling contributed to this report.

Rachel Ohm— 612-2368 [email protected]