Creek Hill Nursery uses beneficials to seek and destroy pest enemies

Features - Pest & Disease

Pesticide resistance is one reason the Pennsylvania nursery turned to a biocontrol program.

Joel DiBernardo, head grower, and Laura Buck, grower and biocontrol manager, release Aphidius ervi, parasitic wasps that control aphids.

Often, taking that first leap of faith into all-new territory proves to be the most difficult part of the journey. Fear of the unknown and thoughts of the “what ifs” can make you second guess your decision.

Joel DiBernardo, head grower at Creek Hill Nursery in Leola, Penn., knows the feeling. In 2010, he started experimenting with biocontrols at the young plant nursery primarily in response to pesticides being taken off the market and problems with insect resistance.

With the nursery’s 500 different perennial plugs comes a diversity of foliage and flowers, and instituting a biocontrol program required a lot of education.

“There was a major learning curve, and the process was so completely different from what we’d been doing for years,” he says.

He attended a seminar hosted by Sound Horticulture, a biocontrol firm in Bellingham, Wash., which helped answer a lot of questions, he says.

“We came away from that seminar saying, ‘We can do this,’” he recalls.

The Leola, Pa.-based nursery also hired Sound Horticulture’s Alison Kutz to help get the program started.

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“A consultant can lessen the intimidation of the plethora of wasps, beetles, mites and nematodes, which we now know are ‘good bugs.’ Alison also helped us come up with a cost-effective biocontrol plan,” he says.

One of the biggest lessons learned in the beginning was how to maintain thresholds of the good bugs and how to react differently when a population of whitefly or aphid shows up, he says.

“We learned to apply predators and wait. Sometimes it takes a week or two. That was a tough adjustment,” he adds. “Predators aren’t a quick-release thing. You have to develop a habitat for them and maintain that habitat so they’ll have things to eat and a place to hang out.”

One of the key aspects to a successful biocontrol program is a rigorous scouting plan. Each week, the Creek Hill team scouts crops for both pests and predators.

“When I first told our growers they had to scout weekly and fill out a report, it was a challenge for them not to be dragged down by the monotony,” he says. “Eventually the scouts started seeing all this naturally occurring insect life appear on the plants. Almost weekly, one of the growers would ask, ‘What’s this bug?’ while holding out a leaf. Their enthusiasm is also making this a success.”

Laura Buck, who came to Creek Hill about six years ago, has taken the biocontrol program “to the next level” and is constantly researching and bringing new ideas to the nursery, DiBernardo says.

“Laura is adept at monitoring and identifying pests, as well as learning everything she can about the predators. She monitors all the activity. Her enthusiasm is what makes this program work so well for us,” he says.

The good guys

For fungus gnat larvae, Creek Hill uses Steinernema feltiae, a beneficial nematode that carries bacteria in its intestinal tract. Once a suitable insect host is located, the juvenile nematode enters the insect pest and penetrates into the insect body cavity. There it releases its bacteria, which multiply and kill the host insect. The nursery also uses a predatory mite, Stratiolaelaps scimitus (formerly known as Hypoaspis miles), a soil-dwelling mite that feeds on fungus gnat larvae, as well as thrips pupae.

Amblyseius cucumeris, a predatory mite, is also used against thrips.

To combat shore flies, the nursery employs Dalotia coriaria, a predatory rove beetle that is often found feeding on the insect pests under the bench where moist conditions often breed shore flies.

There are several choices to fight aphid populations, including several predatory wasps for certain aphid species, green lacewings and convergent lady beetles.

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Aphidius colemani and A. ervi are both parasitizing wasps that lay eggs in the aphid body and the larvae feed on the host insect pest. Chrysoperla carnea (green lacewing) eggs are placed on cards that are interspersed throughout the crops. The nursery also releases Hippodamia convergens, the convergent lady beetle, which preys heartily on aphids.

For spider mites, Creek Hill uses predatory mites such as Phytoseiulus persimilis, which feeds on two-spotted spider mites and other mite species; Amblyseius fallacis, which is adequate in cooler weather; and A. californicus, which DiBernardo says works well on waxy leaved plants like Baptisia. Scouts have seen A. fallacis overwintering in flats as well.

To battle whiteflies when first spotted or when pest numbers are low, the nursery uses Eretmocerus eremicus, a parasitic wasp that feeds on the sweet potato and greenhouse whitefly.

The nursery is in its second year of growing banker plants (oat grass) to house cherry oat aphids, which are parasitized by Aphidius wasps, and in turn fly around the greenhouses eating other aphids. This year, the team is setting out the oat grass hanging baskets throughout the greenhouses in February (a bit earlier than last year) and using 10-inch baskets instead of last year’s 8-inch baskets.

This year the nursery built a 6-foot by 3-foot habitat covered with a tobacco cloth to rear the cherry oat aphids.

It’s critical to provide the beneficials with the proper habitat so they’ll remain in the greenhouse. Alyssum and other flowering annuals are placed on the benches as a pollen source for the predatory wasps. And native populations of those wasp species are not only entering, but overwintering in the greenhouses, he says.

“There is a natural balance in the landscape that maintains a threshold of insect populations,” he says. “This idea can be applied to inside the greenhouse.”

As they wrap up their sixth spring with a biocontrol program, the Creek Hill crew has learned some valuable lessons. The nursery has moved away from a cycle of routine drenching of nematodes to weekly applications of different predators.

“We’ll propagate a whole house, and while the mist is on, we’ll apply nematodes at least once or twice,” he explains. “As the mist decreases, we add the Amblyseius cucumeris and strats [Stratiolaelaps].”

Buck is trying a new process this season and spraying nematodes on the foliage instead of the soil. Early spring marked the first experiment, so results aren’t yet available. Since the program started, DiBernardo says he has the most success against mites. Whiteflies are more of a challenge, but there are more predatory wasp species coming to market, he adds.

“The challenges are still there, but our growers are now so much more aware of what is happening in the greenhouses. It’s part of our journey of being a better environmental steward, and it’s just more fun,” he says. “We’re still plant geeks, but now we’re also insect geeks.”

For more: www.creekhillnursery.com