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Funded Project |
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Funding Program:
Regional IPM Grants (S-RIPM) |
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Project Title:
Biotic Factors Associated with the Spread and Suppression of Pink Hibiscus Mealybug |
Project Directors (PDs):
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Lead State: VA Lead Organization: Virginia Polytechnic Institute and State University |
| Research Funding: $77,929 |
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Start Date: May-01-2007 End Date: Apr-30-2009 |
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Pests Involved: Pink hibiscus mealybug |
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Area of Emphasis: pheromone traps |
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Summary:
The pink hibiscus mealybug (PHM) is an important invasive pest of numerous economically important ornamentals, tree fruits and vegetables. Since arriving in south Florida in 2006, PHM has spread to 36 counties and continues to expand it geographic range in Florida at a rapid rate. Validating predictions of its spread to other southern States, PHM was confirmed on hibiscus plants in three cities in Louisiana in October, 2006 and its invasion of several other southern States is considered likely. Compliance with the zero-tolerance policy for PHM in Florida nurseries is primarily achieved through intensive and extensive reliance on pesticides. Although introduced parasitoids and an endemic predator are being used to suppress PHM in managed urban landscapes, they do not bring populations to extinction. The natural dispersal of PHM on a local scale represents an on-going risk to commercial nurseries, other agricultural enterprises and managed urban landscapes, although its dispersal capabilities or the magnitude of risk that this represents have not been adequately addressed. Further, there is no information on the factors that influence the rate at which PHM colonizes new hosts, the rate at which natural enemies locate and suppress newly-established infestations or the persistence of such suppression. To date, sex pheromone traps for PHM have been used only to detect populations and to measure seasonal changes in abundance. The information content of data from pheromone traps could be greatly increased by developing relationships between the number of male PHM captured and other aspects of its population dynamics, including those associated with its spread and suppression. The primary, overarching goal of this project is to significantly improve the utility of pheromone traps for measuring, predicting and mitigating the risk of infestation of horticultural and agricultural enterprises and managed urban landscapes by PHM. We propose to accomplish this by combining basic studies on the dispersal of PHM with, 1) studies that relate the capture of males in pheromone traps to dispersal, and 2) studies that relate pheromone trap data to the effects of biological control agents under both controlled and natural conditions, including experiments that will provide an initial assessment of the impact of pheromone-based mating disruption on PHM suppression. Specific experiments address: 1) the effect of population density on the capture of males in pheromone traps and crawler dispersal, 2) the dispersal distance of crawlers, 3) the active space of pheromone traps, 4) the latency to infestation of sentinel plants and location of colonies by natural enemies in relation to population density, 5) the rate and persistence of suppression by natural enemies as measured by changes in pheromone trap captures, and 6) the effectiveness of mating disruption compared with biological and chemical control. The proposed research seeks to align closely with the goals of the Southern IPM Center by developing and improving IPM tactics that should ultimately lead to improved efficiency and effectiveness of PHM management and to reductions in pesticide inputs and environmental impacts.
Objectives: The Objectives that we propose to address are captured by the following questions: 1. What are the relationships between the population density of PHM, the number of male PHM captured in sex pheromone traps and the number of dispersing crawlers? 2. What is the dispersal distance of PHM crawlers? 3. What is the active space of traps baited with PHM sex pheromone? 4. What are the relationships between the number of male PHM captured in sex pheromone traps, the latency to infestation of sentinel hibiscus plants and the latency to parasitization and predation of newly established PHM colonies? 5. Does the number of male PHM captured in sex pheromone traps change in response to the release of parasitoids under natural conditions? 6. Can mating disruption suppress populations of PHM and if so, what is the relative effectiveness of different biologically-based control tactics used alone and in combination to reduce PHM population density under controlled, semi-field conditions? |
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Final Report: |
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Results From report submitted by the PI to USDA CRIS report system PROGRESS: 2007/06 TO 2010/06 OUTPUTS: The primary objectives of this project were to investigate factors influencing the localized spread of pink hibiscus mealybug (PHM) via aerial dispersal and to improve the utility of and information content from sex pheromone traps for measuring its population density and suppression in urban environments in south Florida. Ultimately, we sought to relate our findings to the risk of infestation of commercial ornamental nurseries by PHM populations from external sources. In controlled studies, sticky traps were used to examine the dispersal distance of PHM leaving individual, potted hibiscus plants and their dispersal in relation to relative population density and abiotic, environmental variables. Using a similar approach, we attempted to develop a relationship between relative population density, the number of aerially dispersing PHM and the number of males captured in pheromone traps. The relationship between male PHM captures in pheromone traps and the latency to infestation of potted, sentinel hibiscus plants was investigated at 21 residential sites in each of two years. Sex pheromone traps were used to examine the temporal effects of pesticide treatments and the release of biological control agents on male captures at replicated field sites. The effects of trap elevation, placement in relation to host plants and time of day on male captures in pheromone traps were determined and we attempted to measure the distance over which male PHM respond to a pheromone trap. Field-cage trials examined the individual effects of a predator, a parasitoid, a pesticide and mating disruption on PHM populations on individual potted hibiscus plants. An ancillary study compared the expression of injury symptoms from PHM feeding among several commercially important hibiscus cultivars. Research results were presented at Annual Meetings of the Entomological Society of America (2007, 2008), the Kanuga Workshop on Ornamental Diseases and Pests (Hendersonville, NC 2008), the Annual Meeting of the Florida Entomological Society (2008) and the University of Florida Tropical Research and Extension Center Seminar Series (2009). During the project, Catharine Mannion presented numerous seminars to extension agents, landscape company personnel, pest control operators and nursery plant growers on the identification, monitoring and management of invasive insect pests of ornamentals, which included information on PHM that was generated by this project. PARTICIPANTS: Chris Bergh, Virginia Tech, acted as Project Director and was responsible for implementation and oversight of all activities. Catharine Mannion, University of Florida, acted as a Co-Investigator. The research was conducted from Mannion's laboratory at the University of Florida's Tropical Research and Extension Center (TREC), Homestead, FL. PhD student, Justin Vitullo, was hosted by Mannion and the TREC. Mr. Luis Aristizabal was supervised by Mannion during the final year of rhe project. Aijun Zhang, USDA Beltsville, acted as a project collaborator and was responsible for providing PHM sex pheromone for the research. Additional financial support for Vitullo was provided by an internal USDA-ARS award to Zhang and Bergh. Bergh and Zhang co-advised Vitullo and Mannion provided oversight to his day-to-day activities in Florida. Ms. Gangadai Azore, Florida Department of Agriculture and Consumer Services, was a project cooperator, providing biological control agents for some experiments and advise on field site selection. Mr. J. Cou, Garden Depot, Miami, FL, donated potted hibiscus plants for all experiments. TARGET AUDIENCES: Our primary target audiences were Florida Cooperative Extension personnel, and all commericial producers and managers of ornamental plants in Florida. Our results were made known to the Florida Department of Plant Industry, which has been responsible for the PHM biological control program and to USDA APHIS personnel responsible for monitoring the distribution of PHM in the continental USA. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period. IMPACT: 2007/06 TO 2010/06 This project has provided comprehensive information on the short-range dispersal of PHM, operational factors associated with the use of PHM pheromone traps and the interpretation of trap data. Its primary impact is a significantly improved knowledge base about key aspects of PHM biology and behavior that influence its pest status and our monitoring and intervention capabilities. Demonstration of PHM crawler dispersal capabilities and the influence of wind direction on dispersal provide important indications of potential risk to ornamental nurseries. Sex pheromone traps deployed at 40-50 residences in Miami-Dade County in 2006 and 2007 revealed PHM at all locations, with large variation in captures among sites. High percentages (43-86%) of sentinel hibiscus plants deployed at residential sites became infested; no plants at sites without PHM hosts nearby became infested. Importantly, the latency to expression of injury by the sentinel plants was unrelated to male captures in traps. If a relationship exists between PHM population density, the number of dispersing crawlers and male captures in traps, it remains vague and elusive. We attempted to measure the distance over which males respond to pheromone by encircling a trap with infested hibiscus plants at varying radii, but captures were consistently low. At replicated field sites, there were not temporal effects (over 19 months) on or differences in trap captures between parasitoid-release and non-release locations. Similarly, male captures in traps deployed in association with pesticide-treated versus non-treated hibiscus plants showed no treatment effects. Trap elevation and time of day significantly affected male captures. In field cages with infested hibiscus plants, Cryptolaemus montrouzieri and dinotefuran reduced male captures in pheromone traps and captures of females and juveniles in sticky band traps on branches. Two rates of pheromone dispensers deployed in the cages had no effect on mealybug captures in pheromone or sticky band traps. We observed that some hibiscus cultivars in the Florida landscape more severely impacted by PHM than others. When several commercially important hibiscus cultivars were infested with 10 females per plant, fewer Double Red and Snow Queen plants expressed injury than Florida Sunset or Joanne and the latency to their expression of injury and the severity of symptoms were significantly different from the others. These findings are potentially important to the selection of hibiscus cultivars for production and propagation in areas affected by PHM. While the results from our trapping studies provide a strong foundation for future research, the project has raised as many questions about the interpretation of data from sex pheromone traps for measuring and predicting the risk from PHM as it has answered. Our attempt to compare and relate dispersal from plants with different population densities, male captures in pheromone traps associated with those plants and the latency to infestation of sentinel plants at various distances downwind from infested plants was adversely impacted by a hurricane, but remain important questions for future studies. PUBLICATIONS (not previously reported): 2007/06 TO 2010/06 No publications reported this period |
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Outcomes N/A |
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Impacts From report submitted by the PI to USDA CRIS report system This project has provided comprehensive information on the short-range dispersal of PHM, operational factors associated with the use of PHM pheromone traps and the interpretation of trap data. Its primary impact is a significantly improved knowledge base about key aspects of PHM biology and behavior that influence its pest status and our monitoring and intervention capabilities. Demonstration of PHM crawler dispersal capabilities and the influence of wind direction on dispersal provide important indications of potential risk to ornamental nurseries. Sex pheromone traps deployed at 40-50 residences in Miami-Dade County in 2006 and 2007 revealed PHM at all locations, with large variation in captures among sites. High percentages (43-86%) of sentinel hibiscus plants deployed at residential sites became infested; no plants at sites without PHM hosts nearby became infested. Importantly, the latency to expression of injury by the sentinel plants was unrelated to male captures in traps. If a relationship exists between PHM population density, the number of dispersing crawlers and male captures in traps, it remains vague and elusive. We attempted to measure the distance over which males respond to pheromone by encircling a trap with infested hibiscus plants at varying radii, but captures were consistently low. At replicated field sites, there were not temporal effects (over 19 months) on or differences in trap captures between parasitoid-release and non-release locations. Similarly, male captures in traps deployed in association with pesticide-treated versus non-treated hibiscus plants showed no treatment effects. Trap elevation and time of day significantly affected male captures. In field cages with infested hibiscus plants, Cryptolaemus montrouzieri and dinotefuran reduced male captures in pheromone traps and captures of females and juveniles in sticky band traps on branches. Two rates of pheromone dispensers deployed in the cages had no effect on mealybug captures in pheromone or sticky band traps. We observed that some hibiscus cultivars in the Florida landscape more severely impacted by PHM than others. When several commercially important hibiscus cultivars were infested with 10 females per plant, fewer Double Red and Snow Queen plants expressed injury than Florida Sunset or Joanne and the latency to their expression of injury and the severity of symptoms were significantly different from the others. These findings are potentially important to the selection of hibiscus cultivars for production and propagation in areas affected by PHM. While the results from our trapping studies provide a strong foundation for future research, the project has raised as many questions about the interpretation of data from sex pheromone traps for measuring and predicting the risk from PHM as it has answered. Our attempt to compare and relate dispersal from plants with different population densities, male captures in pheromone traps associated with those plants and the latency to infestation of sentinel plants at various distances downwind from infested plants was adversely impacted by a hurricane, but remain important questions for future studies. |
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