Developing beneficial insect habitat for greenhouses

Developing beneficial insect habitat for greenhouses

Summary

A strong and diverse beneficial insect population is necessary to exert pressure on greenhouse pests but greenhouse plants usually do not offer sufficient habitat to sustain such populations. As a result beneficials move on and growers are forced to resort to chemical interventions to protect market-bound plants from pest damage.

This project sought to demonstrate that a habitat of continuously blooming plants would attract and support reproduction of both wild and commercially introduced natural enemies of greenhouse pests. Three sites participated in this trial: 1) a 30-acre, 10-greenhouse operation in central New York called Bakers Acres, 2) a research greenhouse at Cornell University, and 3) a research greenhouse at the University of Vermont.

We selected plants that, together, offered beneficials harborage and season long sources of pollen and nectar, and grouped them in hanging baskets called “Habitat Plant Systems.” These pots, which contained Marigolds (for pollen and Orius harborage), Alyssum (for cool season pollen and nectar), Lantana (for hot season pollen and nectar) and a Barley-cereal aphid banker plant (an aphid natural enemy support), were distributed throughout 2 of the 3 trial greenhouses. Commercially raised Orius and Aphidius were released in April into the greenhouses.

We scouted from April to August, observing and recording the presence of natural enemies (both commercially introduced and wild), and pests in and around the Habitat Plants Systems to determine whether offering habitat was an effective way to attract and sustain populations of beneficial insects.

Objectives/Performance Targets

• Create “Habitat Plant Systems.” Select plants that offer blooms and pollen such as Marigold, Sweet Alyssum, Lantana, and Fennel. Include a banker plant, such as Barley infested with commercially grown cereal aphids to provide an additional source of food for aphid natural enemies.

  Demonstrate effectiveness of Habitat Plant Systems in attracting and retaining natural enemies in greenhouses for the biological control of thrips, whiteflies and aphids:
  Determine whether Habitat Plant Systems provide a favorable habitat (i.e., enough pollen, nectar and alternate hosts) to support the establishment of introduced beneficial insects such as Orius and Aphidius.

  Determine whether Habitat Plant Systems provide a favorable habitat (i.e., enough pollen, nectar and alternate hosts) to attract and support a diverse wild natural enemy insect complex (such as lacewing larvae, Aphidoletes, aphid parasites and Syrphid flies).

Accomplishments/Milestones

IPM Laboratories/Bakers Acres

Below are the results from our trial with Bakers Acres, a commercial greenhouse grower in Central New York. We chose their 30’x100’ herb greenhouse (a nectar and pollen poor greenhouse) as our trial site and used their stock herb greenhouse as the control.

The Habitat Plant Systems served double duty in thrips control by both supporting the reproduction of Orius and attracting thrips into the pots.

A final survey of the Habitat Plant Systems on August 11, 2005, noted 123 Orius and 321 thrips on 149 flowers (marigold, lantana, and alyssum). We count this kind of establishment of Orius to be a major success, and hope that the data that we gathered will give us a basis to understand the predator prey interaction that we need to maintain low thrips populations. It is likely that the average number of Orius per flower will always hover around 1 in order to minimize cannibalism among the Orius. The literature states that Orius kill 5 to 20 thrips per day. Therefore, and average of 2 thrips per flower should not be alarming as long as that HPS are more attractive to thrips than the actual greenhouse crop. However, these kind of data are extremely alarming to the conventional pest manager.

Aphid natural enemies reproduced so dramatically on the Barley banker plant systems that we never saw large numbers of aphids anywhere on the retail herbs all season. The large upsurge in aphid parasite numbers was demonstrated by more than 400 aphid parasites caught on our 2 yellow sticky cards between May 26 and June 6. Evidence of aphid demise on the herbs could be seen here and there where a few mummies would dot the herbs with no evidence of live aphids in the vicinity. Aphid parasites were observed on patrol for the rest of the season in the trial herb house. In contrast, the parasitic wasp catch on the yellow sticky cards in the control herb greenhouse was almost zero all season and almost no live parasites were observed either.

Whitefly natural enemy establishment on the Habitat Plant Systems also occurred because one of the Habitat plants, Lantana, is among the most prolific producers of whitefly in the greenhouse. True to form, when it was placed in the Habitat Plant System, it brought its own greenhouse whitefly. Three weekly introductions of Encarsia followed the introduction of these Lantana plants into the herb house Habitat Plant Systems. The final Habitat plant survey on August 11 showed no whitefly evidence on the younger leaves of the Lantana, and frequent parasitized whitefly scales on the older leaves. No adult whiteflies were seen on any of the Habitat Plant Systems, although an occasional whitefly could be seen in the greenhouse.

The grower had reported in November 2004, before the start of the project, that Aphids were her biggest problem and Whiteflies her second biggest problem in the herb house. Her records showed that in April 2004 and April 2003 she treated with Botanigard for Aphids and a few Whitefly. Then in July both years, she treated the herbs with Safer’s Soap for Aphids. In 2005, the grower still used Botanigard and horticultural oil in early April, just before we installed the beneficials on the Habitat Plant Systems. However, she never felt the need to treat the herb house for Aphids or Whiteflies in July. On the other hand, Thrips became enough of a problem to treat with Conserve on June 23.

University of Vermont

For this study the University of Vermont chose two research greenhouses: their Best Management Practices greenhouse was the trial site and their Conventional greenhouse was the control. Each greenhouse is 30×50 ft. Their Habitat Plant Systems contained Barley, Alyssum, English Daisy, and Lemon Gem, Hero Yellow and Antiqua Yellow Marigolds. UVM used a slightly different strategy, placing Habitat Plant Systems in both trial and control houses and releasing beneficials only in the trial house.

Below are some of their observations:

Beneficials (Orius insidious and Aphidius colemani) were released in the trial greenhouse only. When native (wild) beneficials (Orius, Aphidius, Syrphids and others) turned up in the control house they were found on the Habitat Plant Systems.

Total Insect Occurrences: The following beneficial insects were found on the Habitat Plant Systems in UVM’s trial greenhouse: Orius (21 occurrences), Aphidius (172 occurrences) and Encarsia (2 occurrences). Most notable, however, was the appearance of wild Syrphids (10 occurrences) on the Habitat Plant Systems despite the house being screened to exclude infiltration by wild insects.

The Syrphids were observed hovering around the Alyssum.

Thrips presence was higher in the control house than in the trial greenhouse.

Western flower thrips were lower in the trial greenhouse possibly as a result of suppression by beneficial insects within the Habitat Plant Systems.

In the trial greenhouse, barley had the highest overall insect occurrences followed by Lemon Gem Marigolds, Alyssum and English Daisies.

Lemon Gem Marigolds may have offered the most pollen of all the Habitat Plant species, which might account for the higher numbers of thrips and Orius observed there.

More insects were found on Barley banker plant (part of the Habitat Plant System) primarily due to the inoculation of these plants with the Bird Cherry Aphids that were used to sustain the introduced population of Aphidius within the greenhouse.

There were no insects found on the Barley plants in the control house. It appears that Barley attracts insects only when it functions as a banker plant (which turns it into an insectary).

Aphidius was the most dominant beneficial presence on the Habitat Plant Systems in the trial greenhouse followed by Orius and wild Syrphids.

During the duration of the experiment, routine scouting found Orius on other plants on three occasions where their presence on the bench was in the vicinity of the Habitat Plant Systems overhead.

In the control house, where no beneficials were released, native (wild) Orius and Aphidius were found on the English Daisies and Lemon Gems.

While the Habitat Plant Systems were in the greenhouse the Aphidius population was the highest it had been all year.

Throughout the duration of the experiment, aphid mummies were always present on all the Habitat Plant Systems at a medium to high density.

Cornell University

Cornell University has completed one controlled trial of Orius on marigolds. Although the methodology is not appropriate to the Results section, the fact that this methodology is a controlled scientific trial (in comparison to the IPM Labs and UVM commercial greenhouse demonstrations) is significant for us. We hope to learn some in-depth population information from their endeavor. This trial is being replicated in January and February and will be reported on in the final report. Each trial is being conducted in 4 small greenhouses each containing 3.7 m2 of bench space. The treatments are

I. crop + thrips
II. crop + thrips + marigolds
III. crop + thrips + Orius
IV. crop + thrips + Orius + marigolds

The crop is a fast-growing thrips-producing plant Roma bean. The marigolds are cultivar Bonanza Bolero. In the first replicate, when the bean plants were 12 days old, 10 adult female thrips were introduced to each of 8 bean plants per house. The houses with the Orius treatment had 20 adult female Orius and 5 adult male Orius added. The houses with the marigolds had 4 pots with two flowers each. Unfortunately, as with the first Orius introduction at Baker’s Acres, the marigolds were not fully blooming and abundant pollen was not available. In week 3, the observation of a single Orius nymph in a marigold flower and 4 adults from all the marigold flowers in the 4th treatment did indicate that reproduction had indeed taken place, but the thrips numbers were so high at that point, that they decided to abort the trial. In comparison, in the 3rd treatment where Orius were released in the absence of marigolds, all Orius had disappeared by week 3.

The Cornell researchers felt that the summertime reproduction of wild thrips in their greenhouses confounded their results. A winter trial will rule out the possibility of such interference by wild thrips.

Impacts and Contributions/Outcomes

Augmentation and Conservation

Augmenting and conserving beneficials are critical components of an effective integrated pest management program. This project showed that pest managers and greenhouse growers can sustainably attract natural pest control agents by practicing habitat management. Supporting the plants that support the beneficials that control pests enables growers to remain or become “green” by reducing their reliance on reactive pest control measures, such as pesticide use.

Augmentation: In two of three trials the Habitat Plant Systems attracted and supported a diverse population of beneficials, both commercially reared (Orius and Aphidius) and wild (Syrphid flies, lacewing larvae, lady beetles and Aphidoletes). In one trial wild Syrphids found the habitat plants almost as soon as the doors to the habitat greenhouse were opened for ventilation and in another trial Sryphids were discovered during scouting despite screens designed to keep wild insects out.

Augmenting natural enemies increases the chances of successful pest management through biological control. It shifts the emphasis from reactive to proactive pest management, and encourages beneficials-centric instead of pest-centric management. While reactionary biological control starts at the first sign of the pest (which can be risky if the pest is not promptly detected), habitat can allow the grower to introduce some natural enemies before the pest appears.

Greenhouse growers do not have to change their pest management practices to incorporate habitat in their greenhouse and there is little to no learning curve. Growers already have a strong knowledge of plant maintenance and very likely have habitat-appropriate plants in their greenhouses. Growers just need to use certain plants or varieties of plants as natural repositories for beneficial insects.

The economic feasibility of including habitat plants in the growing environment adds to the attractiveness of this method and further speaks to its sustainability. Start up costs are very small.

Conservation: In one house we were able to demonstrate the successful conservation of natural enemies despite treating the test house with pesticides. We did this by removing the Habitat Plant Systems (and as a result many of the beneficials living on them), before the house was sprayed with an insecticide in late July for the control of thrips. After the greenhouse was treated the hanging plants were returned. Scouting a week later revealed that most of the beneficials had survived the event despite the fact that a beneficials-toxic pesticide was used.

Conservation of beneficials means the grower’s economic investment in pest management is protected. Another impact of this demonstration is that greenhouse growers do not have to abandon all pesticide use in order to successfully use beneficials. Maintaining beneficials habitat is compatible with combination programs that use multiple forms of pest control (true IPM).

Scouting Methodology

Scouting confirmed that aphid, whitefly, and thrips natural enemies (both wild and commercially reared) were attracted to the Habitat Plant Systems. As pests and beneficials congregated on and around habitat plants, we began to wonder if these plants can give us a microcosmic view of the status of biological control in the greenhouse. If this is true, habitat plants may also save growers scouting time. By referring to these habitat plants alone, growers may be able to make timely and accurate pest control decisions without having to scout the entire growing area. We would like to investigate this finding further in a 2006 study as we believe this approach requires research into optimal ratios of natural enemies and pests.

High Resolution Photographs of Beneficial Insects

Just as the Habitat Plant Systems provide a concentrated focal point of insect presence in the greenhouse they also afford an excellent opportunity to photograph normally elusive beneficials. We brought three Habitat Plant Systems (loaded with beneficials) from our trial greenhouse to biological photographer Joe Ogrodnick’s laboratory at the NYS Agricultural Experiment Station. Joe was able to produce nine high resolution, color digital photos of beneficials in all stages of development. These textbook quality photographs will be submitted with our Final Report, and used in presentations, articles, and other educational outreach efforts.

Marketing

Each of the plants contained in the Habitat Plant System was marketed at Bakers Acres under the name Blooms for Beneficials™. Blooms for Beneficials™ laminated signs, complete with an artist’s watercolor rendition of either a marigold, lantana, fennel or alyssum in bloom were distributed throughout the operation where individual habitat plants were being sold. This extended the education process beyond the test greenhouse throughout the entire operation and indicated to customers which plants are known to offer habitat to natural enemies.

We used this project to educate Bakers Acres and its customers on how plants can be used to leverage the power of natural enemies by providing the resources necessary to allow beneficials to remain and reproduce.

As a result of participating in this project, Bakers Acres was able to demonstrate their commitment to sustainable growing principles and practices, and educate their customers as to why sustainability in agriculture matters.

New Product Development

Product One: The barley-cereal aphid banker plant attracted and supported aphid natural enemies so effectively that IPM Laboratories has decided to add this system to its 2006 product line.

This will be the first time this banker plant system will be produced and marketed in the United States. (It has been produced and marketed in Canada for several years.) IPM Labs has received APHIS permits for interstate movement of this banker plant system throughout the Northeast.

Product Two: In the early season, when the Habitat Plant Systems were more advanced than the general hanging baskets, customers repeatedly asked if they could buy the habitat plants which were distributed throughout Bakers Acres trial greenhouse, their herb house. Although habitat plants are not new, selling plants for the express function of providing habitat for beneficials is. As a result of this project, Bakers Acres will create extra Habitat Plant Systems for trial sale in 2006.

Education and Outreach

This grant project, preliminary results and data were presented at the following conferences:

Association of Educational Research Greenhouse Curators (AERGC) Annual Meeting, “Managing Historical Collections: The Plants and The Pests.” New York City. July 25-28, 2005. Approximately 100 members attended our presentation titled “Adventures in Creating Greenhouse Habitat for Beneficials.”

Association of Zoological Horticulture (AZH) 2005 conference “Growing Sustainability.” Chicago. September 17-21, 2005. Approximately 70 members attended our presentation entitled “Adventures in Creating Greenhouse Habitat for Beneficials.”
2005 New England Vegetable and Fruit Conference. Manchester, NH. December 14, 2005. “Successful Biological Control of Insects and Mites in Tomato Greenhouses.” Approximately 50 people attended our presentation.

Tri-state Greenhouse IPM Program 2006 Hands-On Workshop. “Plug Production A-Z and Novel Strategies for Integrated Pest Management.” January 4-6, 2006. Manchester, ME, Durham, NH and Burlington, VT. This day-long program will be presented in each state and is designed to enable greenhouse growers, extension specialists and professional pest managers the opportunity share and discuss best practices and emerging IPM issues. NeSARE grant project leader, entomologist Carol Glenister and trial participant, horticulturalist Cathy Kessler will discuss using banker and habitat plants to attract natural enemies in their presentation “Strategies to Enhance Biological Control: Banker and Habitat Systems.” As of December 30, 120 participants have registered for these workshops.

Mid-Atlantic Fruit and Vegetable Convention “Beneficials in the Greenhouse.” Hershey, PA. January 31, 2006

Workshop: 15 people attended a workshop at Bakers Acres. Included in the class was a tour of the herb house complete with hanging Habitat Plant baskets, a presentation on how the use of habitat can influence the diversity of natural enemies in the garden and greenhouse, and a hands-on lesson in preparing their own habitat systems which they took with them.

Collaboration

Before this project we did not have an opportunity to collaborate with the two horticulturalists at Bakers Acres. We discovered that our combined entomological and horticultural knowledge worked synergistically and strongly contributed to the successful creation and maintenance of the Habitat Plant Systems. Reenie Sandsted and Cathy Kessler, of Bakers Acres, selected the lantana to provide pollen and nectar during the hot summer months. They also maintained the Habitat Plant Systems so that most of the plants survived throughout the season. A major breakthrough occurred when Reenie’s automatic response to normally overcrowded barley banker plants was to break one banker plant into 26 very small units and place one unit in each of the habitat plant baskets. Those barley units lasted all summer long while the original (unsegregated) banker plant was dead within 10 weeks due to crowding.

Other Projects

This project demonstrated that habitat attracts and supports beneficials, enticing them to establish themselves in the greenhouse. Our next goal is to demonstrate that habitat- dwelling beneficials sufficiently control a variety of greenhouse pests, naturally and sustainably. Additional work will be needed to determine which plant/beneficial combinations work best for specific greenhouse crops, like tomatoes or poinsettias.

Collaborators: