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Biological warfare: How growers are attacking geenhouse pests with beneficial bugs

  • Andrew Cowles of Andrew's Greenhouse shakes a plant over a white sheet of paper to demonstrate how to see what "good" or "bad" bugs are at work.<br/>KEVIN GUTTING

    Andrew Cowles of Andrew's Greenhouse shakes a plant over a white sheet of paper to demonstrate how to see what "good" or "bad" bugs are at work.
    KEVIN GUTTING Purchase photo reprints »

  • Andrew Cowles of Andrew's Greenhouse uses beneficial insects and other biological controls of pests and diseases in his commercial greenhouses.<br/>KEVIN GUTTING

    Andrew Cowles of Andrew's Greenhouse uses beneficial insects and other biological controls of pests and diseases in his commercial greenhouses.
    KEVIN GUTTING Purchase photo reprints »

  • These packets of live predatory insects are one biological method that Andrew Cowles of Andrew's Greenhouse uses to control pests and diseases in his commercial greenhouses.<br/>KEVIN GUTTING

    These packets of live predatory insects are one biological method that Andrew Cowles of Andrew's Greenhouse uses to control pests and diseases in his commercial greenhouses.
    KEVIN GUTTING Purchase photo reprints »

  • Andrew Cowles of Andrew's Greenhouse shakes a geranium to demonstrate how to see what "good" or "bad" bugs are at work. An even more telling way, for especially small pests, is to shake the plant over a white sheet of paper.<br/>KEVIN GUTTING

    Andrew Cowles of Andrew's Greenhouse shakes a geranium to demonstrate how to see what "good" or "bad" bugs are at work. An even more telling way, for especially small pests, is to shake the plant over a white sheet of paper.
    KEVIN GUTTING Purchase photo reprints »

  • These packets of live predatory insects are one biological method that Andrew Cowles of Andrew's Greenhouse uses to control pests and diseases in his commercial greenhouses.<br/>KEVIN GUTTING

    These packets of live predatory insects are one biological method that Andrew Cowles of Andrew's Greenhouse uses to control pests and diseases in his commercial greenhouses.
    KEVIN GUTTING Purchase photo reprints »

  • These "banker" plants which attract - and are covered with - aphids are one of the biological methods Andrew Cowles of Andrew's Greenhouse uses to control pests and diseases in his commercial greenhouses.<br/>KEVIN GUTTING

    These "banker" plants which attract - and are covered with - aphids are one of the biological methods Andrew Cowles of Andrew's Greenhouse uses to control pests and diseases in his commercial greenhouses.
    KEVIN GUTTING Purchase photo reprints »

  • This is a reference guide to some of the beneficial insects (in white) that Andrew Cowles of Andrew's Greenhouse uses to control pests (highlighted in green) and diseases in his commercial greenhouses.<br/>KEVIN GUTTING

    This is a reference guide to some of the beneficial insects (in white) that Andrew Cowles of Andrew's Greenhouse uses to control pests (highlighted in green) and diseases in his commercial greenhouses.
    KEVIN GUTTING Purchase photo reprints »

  • This is a reference guide to some of the beneficial insects (in white) that Andrew Cowles of Andrew's Greenhouse uses to control pests (highlighted in green) and diseases in his commercial greenhouses.<br/>KEVIN GUTTING

    This is a reference guide to some of the beneficial insects (in white) that Andrew Cowles of Andrew's Greenhouse uses to control pests (highlighted in green) and diseases in his commercial greenhouses.
    KEVIN GUTTING Purchase photo reprints »

  • This is a reference guide to some of the beneficial insects (in white) that Andrew Cowles of Andrew's Greenhouse uses to control pests (highlighted in green) and diseases in his commercial greenhouses.<br/>KEVIN GUTTING

    This is a reference guide to some of the beneficial insects (in white) that Andrew Cowles of Andrew's Greenhouse uses to control pests (highlighted in green) and diseases in his commercial greenhouses.
    KEVIN GUTTING Purchase photo reprints »

  • These packets of live predatory insects are one biological method that Andrew Cowles of Andrew's Greenhouse uses to control pests and diseases in his commercial greenhouses.<br/>KEVIN GUTTING

    These packets of live predatory insects are one biological method that Andrew Cowles of Andrew's Greenhouse uses to control pests and diseases in his commercial greenhouses.
    KEVIN GUTTING Purchase photo reprints »

  • Andrew Cowles of Andrew's Greenhouse points to a thrips, a species that damages plants and flowers but also can be a carrier of viruses such as the Tomato Spotted Wilt Virus. Cowles uses predatory mites and other biological means to control pests like these.<br/>KEVIN GUTTING

    Andrew Cowles of Andrew's Greenhouse points to a thrips, a species that damages plants and flowers but also can be a carrier of viruses such as the Tomato Spotted Wilt Virus. Cowles uses predatory mites and other biological means to control pests like these.
    KEVIN GUTTING Purchase photo reprints »

  • Purchase photo reprints »

  • Andrew Cowles of Andrew's Greenhouse shakes a plant over a white sheet of paper to demonstrate how to see what "good" or "bad" bugs are at work.<br/>KEVIN GUTTING
  • Andrew Cowles of Andrew's Greenhouse uses beneficial insects and other biological controls of pests and diseases in his commercial greenhouses.<br/>KEVIN GUTTING
  • These packets of live predatory insects are one biological method that Andrew Cowles of Andrew's Greenhouse uses to control pests and diseases in his commercial greenhouses.<br/>KEVIN GUTTING
  • Andrew Cowles of Andrew's Greenhouse shakes a geranium to demonstrate how to see what "good" or "bad" bugs are at work. An even more telling way, for especially small pests, is to shake the plant over a white sheet of paper.<br/>KEVIN GUTTING
  • These packets of live predatory insects are one biological method that Andrew Cowles of Andrew's Greenhouse uses to control pests and diseases in his commercial greenhouses.<br/>KEVIN GUTTING
  • These "banker" plants which attract - and are covered with - aphids are one of the biological methods Andrew Cowles of Andrew's Greenhouse uses to control pests and diseases in his commercial greenhouses.<br/>KEVIN GUTTING
  • This is a reference guide to some of the beneficial insects (in white) that Andrew Cowles of Andrew's Greenhouse uses to control pests (highlighted in green) and diseases in his commercial greenhouses.<br/>KEVIN GUTTING
  • This is a reference guide to some of the beneficial insects (in white) that Andrew Cowles of Andrew's Greenhouse uses to control pests (highlighted in green) and diseases in his commercial greenhouses.<br/>KEVIN GUTTING
  • This is a reference guide to some of the beneficial insects (in white) that Andrew Cowles of Andrew's Greenhouse uses to control pests (highlighted in green) and diseases in his commercial greenhouses.<br/>KEVIN GUTTING
  • These packets of live predatory insects are one biological method that Andrew Cowles of Andrew's Greenhouse uses to control pests and diseases in his commercial greenhouses.<br/>KEVIN GUTTING
  • Andrew Cowles of Andrew's Greenhouse points to a thrips, a species that damages plants and flowers but also can be a carrier of viruses such as the Tomato Spotted Wilt Virus. Cowles uses predatory mites and other biological means to control pests like these.<br/>KEVIN GUTTING

Organic gardening methods, especially in vegetable gardens, are mushrooming in popularity and chemical pesticides are being phased out by most home gardeners.

But it is much more of a challenge to use organic pest controls in the hot, humid atmosphere of a commercial greenhouse. Still, some growers, like Andrew Cowles of Andrew’s Greenhouse in South Amherst, are “going green.”

Four years ago, Cowles decided to switch from chemical sprays to biological control agents — getting natural enemies of plant pests to do the work for him.

“It was the cost of chemicals and me having to spray at regular intervals,” Cowles said, explaining his decision.

“Growers don’t want to spray and we can’t spray when the customers are in the greenhouse, so we have to do it at night,” which meant long hours for Cowles.

The use of beneficial insects to control pest insects has been increasing throughout the nursery industry, Cowles said. “We have so much better information and have learned a lot about beneficials,” he said.

Taking the plunge

Whiteflies, aphids, shore flies, fungus gnats, mealy bugs, thrips and mites are the bane of greenhouse owners like Cowles. He knew he needed to employ parasitical wasps, nematodes, predatory mites and rove beetles in order to combat the pests. But going cold turkey without chemicals can be a bit scary and he wanted lots of advice.

His greenhouse supplier recommended he contact Biobest Biological Systems in Toronto, Canada, to get started. Ron Valentine is the Biobest agent with whom Cowles works. Greenhouses in Canada, especially those for vegetable growers, have been involved in biological controls for a long time.

Valentine, who is originally from the Netherlands where biological controls have been employed for years, comes down from Canada every three or four months to assess the situation and give advice. “Ron is a teacher,” Cowles said with admiration. “It’s like going back to school with him. He has so much knowledge.”

The Biobest agent has taught Cowles how to recognize the specific insect pests that attack his greenhouse plants. Often this can be critical. For instance, Cowles thought he had a problem with green peach aphids and bought the recommended parasitical wasp to control it. But the situation wasn’t alleviated. Valentine visited and using a hand lens informed Cowles that he didn’t have a green peach aphid problem but rather a potato aphid pest.

“How can you tell?” Cowles asked Valentine.

The agent pointed out that the minute insect had longer antennae and other barely discernible differences. Switching to another miniscule wasp that devours potato aphids solved the problem.

Grow your own

Before you get worried about going into a greenhouse where wasps are at work, rest assured they don’t sting. In fact, “the wasps are so tiny you can’t see them,” Cowles said. Customers won’t even know they are there.

Cowles needs to provide food for his hard-working wasps so he actually “grows” aphids to get the good insects started. He plants oats as a “banker plant” to create a mass of aphids to feed the wasps. He covers the plant with a fine netting to concentrate the pests in one place. Then he carries the banker plant to an area he needs protected, removes the netting and releases the wasps he has purchased. They get a quick aphid dinner to prime their activity and then they fly throughout the greenhouse having a delicious dessert and more meals on the aphids that have appeared on the plants he wishes to sell.

“It keeps the aphid population down to zero,” Cowles said.

Thrips is the biggest problem in his greenhouses, Cowles said. (Note that the proper name of the insect is thrips in the singular. The plural is also thrips.) These tiny insects are fond of verbena, ivy geranium, impatiens, peppers and other plants. They carry a viral disease which also hurts the plants. Cowles said he sometimes would hear from a customer, “That plant you sold me just isn’t growing.” Immediately, Cowles would suspect thrips, which sap the plant’s strength without dramatic symptoms like dead leaves or damaged flowers.

Thrips look like a tiny little cigar. Once when Cowles was having a problem with them, Valentine noticed during a visit that there was an errant impatiens plant growing under a bench in the solar greenhouse. No one had noticed it. But Valentine pointed out that it was harboring a lovely population of thrips.

Clean is key

Keeping a clean greenhouse has always been a mantra for Cowles. But now he is becoming obsessive about it. He has learned that the larvae of certain greenhouse pests can be found in the otherwise clean stones and soil under the greenhouse benches. So every year staffers laboriously remove the stones and soil and sift through the material, dumping the residue outside. Thrips can be controlled very well this way.

Remove weeds from under the benches, Cowles advises. “That’s where problems can occur.” That errant impatiens wasn’t a weed but it was harboring insect pests anyway.

Another simple technique you can use at home can control two-spotted mite, a major problem in greenhouses and for home gardeners with house plants. Mites cause stippled foliage as they suck juices from the plant.

“Florida is infested with two-spotted mite and we get some plants from Florida,” Cowles explained.

Valentine told Cowles, “You don’t need to have something complicated.” Cowles added, “Ron is the kind of person who tells you the little tidbits.” The simple technique Valentine taught him is to grow garden beans in a pot next to his ornamental plants. “If there is two-spotted mite in your greenhouse they will go for the beans first. Eventually the bean plant turns yellow and you take it out and destroy it,” he said.

At home, sow six or seven bean seeds in a pot and tend them carefully. “It’s fun for the family to grow beans,” Cowles commented, even if you don’t want to eat what’s in that pot.

Cowles also uses beneficial nematodes, which look like microscopic worms. When flats of plant plugs (rooted cuttings) arrive from a wholesale supplier, greenhouse staffers dip each flat into a big tub of water in which the nematodes are swimming. The worm-like creatures saturate the flats and can destroy any harmful insect eggs and larvae which hitchhiked from the wholesaler. The main problems, Cowles said, are from Florida greenhouses, especially mandevilla and other tropical annuals which are prone to two-spotted mite. They automatically get the nematode treatment.

In addition, when the plugs are potted up, they each get a mite sachet on top of the soil. Each inch-square sachet is filled with a mite predator which can crawl in and out of the sack through a tiny hole. If your calibrachoa hanging basket comes with such a sachet, leave it in the pot and it will keep working through the summer, Cowles said.

Insect sprinkles

All the predatory and parasitic beneficial insects arrive by overnight express from Canada in plastic bottles, tall cardboard tubes or boxes of mite sachets. They must be released into the greenhouse immediately before they die from lack of food.

Cowles methodically goes through his greenhouses sprinkling the tiny insects around his plants. Each morning he tours the greenhouses equipped with a sheet of white paper. He picks up a plant and shakes it over the paper. Sometimes he needs to use a hand lens to identify the tiny dark specks that appear on the paper. Some will be insect pests. Others will be those friendly beneficials hard at work. They scoot over the paper as fast as they can wriggle.

He also keeps a careful eye on certain kinds of plants that are more prone to insect infestations.

You may have seen yellow sticky traps in greenhouses for a number of years. These are monitoring devices to see whether aphids or whiteflies are present. At Sunny Border Nurseries in Connecticut last fall I saw whole walls of these traps.

Cowles puts up new sticky traps every week but he removes them after three days of monitoring so he doesn’t capture too many beneficial insects which are also attracted to the yellow color of the traps.

Greenhouse owners used to keep their doors tightly shut to prevent unwanted insects from invading. Today that is all changed. The greenhouse doors at Andrew’s Greenhouse are wide open — except in cold weather — to welcome native beneficial insects. “What greenhouse owners didn’t realize was that they were also shutting out native beneficial like wild bees and other pollinators and predators,” Cowles said. “There are so many good bees and wasps out there,” he said, just looking for aphids and thrips to devour.

“The nursery business has gone green,” Cowles concludes. When he announced his decision to try biological controls instead of chemical sprays, some of his staff was skeptical. Now, however, he thinks they’re convinced it is the way to go. It can still be frustrating, however, such as when he thought he had one kind of aphid and the problem was another insect species. It doesn’t always work, either. One year he had to lug dozens of hanging plants to an unused greenhouse and spray them with chemicals to save them.

It takes experience to employ biological control agents well, Cowles admitted, and he is very dependent on Ron Valentine and Biobest for advice. “I talk to other growers and offer help getting started. “Probably half the growers in New England are using beneficial insects,” Cowles said.

Not everyone in our area has converted. However, many institutional and commercial greenhouses at least refrain from chemicals other than organically approved horticultural oil or soap.

“Sometimes it is more expensive and I’m not saving money,” Cowles admitted.

“But I don’t mind spending the money when you know you are doing the right then. This is going in the right direction for our industry. I always want to find new ways for our business to be green.”

Cheryl Wilson can be reached at valleygardens@comcast.net.

Related

Calling the advisers on biological control agents

Monday, April 29, 2013

Andrew Cowles of Andrew’s Greenhouse in South Amherst says that Biobest, with offices in Michigan and Canada, has given him excellent advice as well as supplying him with biological control agents for the past four years. UMass Extension also offers advice to commercial greenhouse growers on biocontrols. Tina Smith is the extension agent in charge of floriculture including greenhouses. Since … 0

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