Enhancement, Implementation - Evaluation of Biologically Based Pest Management Tactic for Three Key Pests in Production Nurseries

Final Report for LNE02-167

Project Type: Research and Education
Funds awarded in 2002: $138,636.00
Projected End Date: 12/31/2006
Matching Non-Federal Funds: $32,651.00
Region: Northeast
State: Maryland
Project Leader:
Dr. Paula Shrewsbury
University of Maryland
Expand All

Project Information


The importance and production of ornamental plants has increased dramatically over the past decade. For example, production of nursery and greenhouse crops is first among all crops in 10 of the 12 states in the Northeast region. Pest management is a major component and challenge in ornamental plant production. This industry is heavily dependent on pesticides, which continue to be its primary pest control method (Hudson 1996). Nursery growers and Integrated Pest Management (IPM) scouts are looking for non-chemical pest management alternatives due to societal, environmental, and regulatory (FQPA) pressures. However, growers and scouts are unwilling to take the risks associated with new methods until they have been demonstrated to be economical, practical, and effective. This project aims to address these needs and reflects input solicited from IPM scouts and nursery growers in Maryland.

The 4 phases of the proposed 4 year project are: 1) research to evaluate the efficacy of, and refine techniques for using a biologically based pest management tactic, 2) a demonstration phase to integrate this and other tactics into a biologically based IPM program in commercial nurseries and evaluate their applicability (efficacy, ease of use, and profitability), 3) an education phase to extend results to end users and increase the likelihood of adoption of these biologically based tactics and IPM, and 4) perform an impact assessment to determine and document changes in practice, knowledge, and attitudes of beneficiaries.


Alternative pest management tactics were compared to conventional tactics for their affect on pest and beneficial arthropods in Maryland production nurseries. Alternative controls included habitat manipulations and augmentative releases of predators. In one container nursery habitat manipulations included groundcover type (weed cloth and hard wood mulch) and container position (pots placed above the ground and pots sunken into the ground [pot-in-pot]) which were manipulated in nursery beds. Generally, wood mulch increased the abundance of alternative prey and natural enemies on the ground but not within the containers at the soil level or on plant foliage. The pot-in-pot method strongly increased abundance of both alternative prey and natural enemies on the ground and within the containers at the soil level, whereas pots above ground had a greater abundance of predators on the foliage. Habitat manipulations differentially affected mortality of soil versus foliar active herbivores. However, herbivores on the soil in containers suffered greater mortality than those on the foliage, regardless of groundcover or pot position. Day and night differences in herbivore mortality and predator taxa were also examined.

In a second container nursery, the effect of container position (pots placed above the ground and pots sunken into the ground [pot-in-pot]) and augmentative biological control (application of entomopathogenic nematodes) on black vine weevil larvae was examined on container grown herbaceous plants. Plants grown using the pot-in-pot method and plants treated with nematodes had fewer black vine weevil larvae than plants grown in above ground pots on those not treated with nematodes.

In a field grown nursery predatory mites were released on Holly shrubs, Ilex sp., at two predator: prey ratios to examine their ability to suppress Southern red mite, Oligonychus illicis. Generally, release of predators did not reduce abundance of Southern red mite compared to the control. Miticide treated plants had consistently lower Southern red mite populations. Leaf damage was less on miticide treated plants. Information from these studies was extended to growers, IPM consultants, and Cooperative Extension personnel through conferences and workshops.

Performance Target:
  1. To refine and evaluate biologically based pest management tactics, habitat manipulations, for their feasibility in increasing generalist predator populations, with a concomitant reduction in pest populations. [gone beyond it]

    We predict that 3 of the 4 commercial nurseries and all 3 of the 3 IPM scouts engaged in the demonstration phase of the project will continue to implement biologically based pest management tactics over chemical tactics. [fallen short] Explanation for falling short: Engaging the nursery cooperators was more difficult than expected, and IPM consultants originally involved in the project changed jobs.

    We predict that 100 of the 250 nurseries in Maryland will increase their implementation of biologically based tactics, and that 25 of the 36 participating Extension personnel in the NE region will increase the number of times they train on biologically based control tactics for one year after participating in SARE education programs compared to the previous year. [fallen short] Explanation for falling short: Nursery stakeholders, and Extension and government personnel were trained. However, our proposed method of follow-up surveys (hard copy mailed surveys to participants) on the adoption of these tactics was more difficult and less effective than first thought.


Click linked name(s) to expand
  • Stanton Gill
  • Colin Stewart


Materials and methods:

This project included a research study at the UMD Upper Marlboro Research and Education Facility, research / demonstration studies in 3 MD production nurseries, and education programs to inform MD nursery growers and NE region IPM consultants and Extension personnel on the use of alternative pest management strategies for production nurseries.

For the research phase field plots simulating production nurseries were used and provided greater control of conditions and flexibility in methods (ex. releasing pests on plants) than the on-farm study. Our objective was to evaluate the efficacy of, and refine techniques for using a biologically based pest management tactic against insect pests. We hypothesize that increasing habitat complexity (habitat manipulation) by covering plots with a wood chips would increase predators and reduce pest density and damage compared to plots without manipulations. We determined the impact of two potting systems (pot in pot and above ground) on natural enemies and pests. Our study system uses 2 key insect pests with different life histories: Hawthorn lace bug, Corythucha cydoniae (Fitch), (a foliar pest) and black vine weevil (Otiorhynchus sulcatus) (larvae are root feeders, adults are foliar pests) on herbaceous plants, which serve as model systems to test this pest management tactic. A randomized complete block design was used with 5 replicates. Study plants were infested with known numbers of herbivores. Pitfall traps and visual monitoring were used to monitor natural enemy abundance and pest insect survival. Arthropods will be identified to family and trophic level. The results from this study was used to engage nursery grower cooperators for the demonstration / research phase of the project.

For the demonstration phase of the project we demonstrated in 3 MD nurseries the efficacy of biologically-based IPM approaches. The program will focus on 3 key insect / mite pests (azalea lace bug, black vine weevil, and Southern red mite) of woody and herbaceous ornamentals. The “habitat manipulation tactic” (wood chip mulch and pot-in-pot planting methods) were implemented in 2 container nurseries. Studies were conducted in nursery beds within the nursery. In one nursery methods were similar to those described above. A study was conducted in a 2nd nursery on container grown herbaceous plants in nursery beds. One half of the plants were grown above ground and half as pot-in-pot. Within each of those treatments one half of the plants received soil applications of entomopathogenic nematodes, Heterorhabditis bacteriophora. The effect of these studies on black vine weevil larvae was determined. In a 3rd nursery augmentative release of predatory mites to control Southern red mite on field grown holly was evaluated.

We engaged the nursery cooperators’ by meeting with them every few weeks and discussing the progress of the study. This helped them see the project’s benefits and sustain their interest. However, they were often busy making it difficult to engage them as much as we predicted we could.

Research results and discussion:

For the research phase of the project our goal was to develop and evaluate biologically based pest management tactics by conducting an applied research project (Performance Target 1). More specifically we determined: 1) the effect of adding wood mulch to nursery beds with container plants of Cotoneaster dammeri compared to weed cloth beds and 2) the effect of plant / pot position (above ground compared to pot in pot) on arthropod (herbivore, alternative prey, natural enemy) taxa and abundance and herbivore (Hawthorn lace bug and black vine weevil) survival. This goal was accomplished.

In the demonstration phase of the project we identified 3 nursery cooperators. In 2003 and 2004, the demonstration phase of the project was implemented (Performance Target 2). This phase integrated biologically based tactics into commercial nurseries and evaluated their efficacy. The goal was to increase the implementation and adoption of biologically based pest management tactics over chemical tactics (Performance Target 2). In one nursery, during 2003 and 2004, we implemented a program targeting the management of azaleas and their key pest, azalea lace bug. We evaluated two habitat manipulations (use of wood mulch ground cover, a pot-in-pot planting system). We further examined the impact of these habitat manipulations on ground active compared to foliar feeding pests. In a second nursery, in 2003 and 2004, we evaluated the use of augmentative releases of predatory mites to manage a key mite pest, southern red mite, on Ilex species. In a third nursery, during 2004, we evaluated the use of the pot-in-pot planting system and entomopathogenic nematodes to manage black vine weevil. These milestones were accomplished. Cooperating nurseries were to adopt alternative practices and this milestone was not accomplished.

In 2005, data from all research and demonstration projects was consolidated and analyzed. A Masters of Science thesis was produced. In 2003, 2004, and 2005, results of the research and demonstration projects were presented to nursery growers at educational programs in MD, other Northeast region states, and nationally (Performance Target 3). Our milestone was that growers would adopt these methods and Extension personnel and IPM consultants would use this information in their training. This milestone was partially met. It is difficult to determine what growers and to what levels they adopted alternative management practices. Approximately 16 Extension personnel trained said they would use this information.

Participation Summary


Educational approach:

As part of the educational / outreach phase of this project, results of the research and demonstration projects were presented at several professional and end-user educational programs throughout the northeast region and nationally in 2003, 2004, 2005, and 2006 (approx. 2,000 professionals trained). These included: 7 presentations at Entomological / IPM professional conferences; 10 University seminars to research and extension faculty, staff, and students; 9 green industry professional association meetings / recertification conferences, 4 Cooperative Extension short courses; and 4 nursery field day held in MD. Evaluations from short courses indicated that participants found the training useful. See the appendices with the survey results from the NE SARE workshop held on Oct. 5th and 6th of 2006 that targeted NE region extension professionals and private consultants. In 2004, an overview of this project was placed on line at http://shrewsburylab.umd.edu. A poster on the effect of habitat manipulations on pest insects and natural enemies on ornamental nurseries was developed and displayed at the Northeast SARE conference in Burlington, Vermont during October 2004. A Master’s thesis was produced from the University of Maryland.

The use of augmentative release of predators in outdoor environments such as field or container nurseries need further studies to identify factors that limit or promote the success of this approach. More outreach has to be conducted to identify measures to get stakeholders to adopt IPM and biological practices.

Additional Project Outcomes

Project outcomes:

Impacts of Results/Outcomes

As part of the research phase of this project, we evaluated biologically based pest management tactic, habitat manipulations, for their efficacy in increasing generalist predator populations, with a concomitant reduction in pest populations and damage (Performance Target 1). In comparing the taxa and abundance of alternative prey and natural enemies in plant containers between ground cover types (mulch vs. weed cloth beds), and pot position (pot in pot vs. above ground pots) we found no effect of mulch. However, natural enemies were greater in pot-in-pot containers than in above ground containers. Individual predators, such as ants, rove beetles, ground beetles, and spiders, and a parasitoid (Scelionidae) were found to be more abundant within pot-in-pot containers than in containers above ground. Arthropods, such as Collembola that likely serve as alternative prey for predatory insects, were also more common in the pot-in-pot position than the containers above ground.

We found that the mulch and weed cloth treatments rarely differed in their effect on survival of hawthorn lace bug nymphs or the eggs and larvae of black vine weevils. We also found that the pot position had a variable effect on hawthorn lace bug survival. However in all experiments, predation of black vine weevil eggs and larvae was dramatically higher in containers in the pot-in-pot versus above ground planting method.

As part of the demonstration phase of this project, we implemented biologically based pest management tactics in 3 nurseries (Performance Target 2). To date the data indicate that ground cover type and pot position had a significant effect on generalist predator (ground and rove beetles, spiders, and ants) and alternative prey abundance within the plant containers, where abundance was greater in wood mulch compared to weed cloth plots, and greatest in the pot-in-pot than above ground planting method. However, there was no significant effect of ground cover type, but there was a significant effect of planting method on herbivore survival (lower survival in pot-in-pot). Herbivores active in the soil (at the soil line) were significantly more susceptible to predation compared to herbivores on the foliage. This effect was slightly enhanced in pot-in-pot plants but ground cover did not influence this effect. Cost and impact evaluations of this program are underway. Studies also found that black vine weevil larval abundance in herbaceous perennial plants was lower in plants using the pot-in-pot system than above ground; and that entomopathogenic nematode applications reduced weevil larval abundance compared to no treatment control plants. Other studies found that augmentative release of predatory mites to suppress Southern red mite on Ilex spp. was not effective. Further studies are needed to improve the efficacy of this management tactic.

These studies provide evidence that habitat manipulations, such as the use of wood mulch ground cover over nursery beds, and the pot-in-pot growing method should increase natural enemy abundance and reduce the abundance of soil dwelling pests in production nurseries. Future research should provide an economic analysis of these practices to promote adoption of these measures by growers.

Assessment of Project Approach and Areas of Further Study:

Areas needing additional study

The use of augmentative release of predators in outdoor environments such as field or container nurseries need further studies to identify factors that limit or promote the success of this approach. More outreach has to be conducted to identify measures to get stakeholders to adopt IPM and biological practices.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.