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Funded Project

Funding Program: Regional IPM Grants (S-RIPM)

Project Title: Integrating Management Of Soft Scales In The Southern Landscape

Project Director (PD): Juang-Horng Chong [1]

Lead State: SC Lead Organization: Clemson University

Cooperating State(s): Georgia, North Carolina, Virginia

Undesignated Funding: $153,896

Start Date: Jul-01-2010 End Date: Jun-30-2013

Summary: This is a research project. The ornamental production and landscape industry in Georgia, North Carolina, South Carolina and Virginia have an estimated value of $3.6 billion. Stakeholders identified scale insects as the most important pests of ornamental plants. The adoption of integrated scale insect management program is hindered by reliance on broad-spectrum insecticides, lack of a degree-day or plant phenological predictive models for pest activity, and lack of knowledge on (1) phenology, (2) the natural enemies and their impacts and (3) the potential of integrating different management tactics. This research project, by using the widely distributed oak lecanium scale as a model species, seeks to fill in the gaps in our knowledge and develop an integrated soft scale management program in the landscape of GA, NC, SC and VA. The objectives of this project are to develop degree-day and plant phenological indicator predictive models for significant life history events, to optimize biological control through better understanding of the natural enemies species composition, seasonal activity and impact, and to integrate chemical and biological control of oak lecanium scale. The goal is to develop sustainable and low-risk approaches to scale insect management. This project addresses the National IPM Road Map focus area of residential and public areas but the results are applicable to other horticultural production and forestry systems in the Southern Region, the US, and the world. The project also addresses the IPM Road Map goals of improving profitability and reducing risks to human and environmental health from pesticide applications. Objectives: 1. Review literature to determine the influence of environmental factors (temperature), host plant and taxonomy on the phenology of soft scales. 2. Develop degree-day and plant phenological indicator based predictive models for oak lecanium scale life history events. 2a. Determine the phenology of oak lecanium scale on established willow oaks in the landscape of GA, NC, SC and VA. 2b. Develop a degree-day predictive model for scale phenology. 2c. Develop a plant phenological predictive model for scale phenology. 3. Optimize natural control of oak lecanium scale provided by parasitoids and predators 3a. Determine the composition and impact of natural enemies in GA, NC, SC and VA 3b. Determine the seasonal activity of natural enemies in GA, NC, SC and VA 4. Integrate chemical and biological control of oak lecanium scale 4a. Assess the impact of foliar spray of selected insecticides on the suppression of scale population and the activity of natural enemies 4b. Assess the impact of new application technologies of neonicotinoids on the suppression of scale population and the activity of natural enemies 4c. Assess the impacts of selective treatment of specific tree sections on scale insect and natural enemy abundance

Final Report:

Results From report submitted by the PI to USDA CRIS report system PROGRESS: 2010/07 TO 2011/07 OUTPUTS: Between 15 July 2010 and 14 July 2011, studies aiming at accomplishing three of the four project objectives have began in all participating states (GA, NC, SC and VA). A graduate research assistant at MS level had been recruited at Clemson University (SC) to complete this project. A literature review on the influence of environmental factors, host plant and scale insect taxonomy is current on-going and as a part of the graduate research assistant's thesis review. A large body of publications on the phenology of scale insects (> 250 peer-reviewed papers) were collected from all available sources and carefully reviewed to correlate the egg hatching time and the annual number of generations of all soft scale insects to their respective taxonomic positions, geographical regions, host plant species and noted environmental conditions. Studies to better understand the seasonal phenology and abundance of the oak lecanium scale in urban landscape (Objective 2) have been conducted in Florence, SC since 2009, while monitoring has begun at one site each in Griffin (GA), Raleigh (NC) and Virginia Beach (VA) in July 2010. Each monitoring site contains 5-10 trees which have been heavily infested by oak lecanium scale. Samples were collected weekly since July 2009 to determine the developmental stage and density of the scale insects at the time of collection. Local ambient temperature was recorded by a weather station near each monitoring site to aid in estimating the degree-days or heat units (based on single-sine method) required by the scale insects to achieve each developmental stage. Local phenology or flowering status of selected plant species (hydrangea, Loropetalum, crape myrtle, and day lily) and other plant species was observed and recorded. Samples of twigs and associated scale insects were also collected and isolated in the laboratory to collect parasitoids emerged from the collected samples. A beat-sheet collecting method was also employed to collect any predators associated with the scale insect infestation. In addition, yellow sticky cards were deployed at each tree to assess the seasonal abundance of natural enemies. The collection of parasitoids and predators was aimed to determine the diversity and seasonal abundance of natural enemies of oak lecanium scale insect in GA, NC, SC and VA (Objective 3). Collected samples have been sent to USDA Systematic Entomology Laboratory for identification and the results are pending. Management of oak lecanium scale in the urban landscapes is most effective when insecticide applications are applied at the time of egg hatch or crawler emergence. Therefore, it is important that the end users of the management information (e.g., nurserymen, landscape care professionals, arborists, extension personnel) be informed of the results of this project. Results were disseminated through education programs, workshops and presentations at various state and regional trade/clientele group meeting or trade shows, as well as scientific meetings. Results were also disseminated through several extension publications. PARTICIPANTS: The PIs (Juang-Horng Chong, Clemson University; Kris Braman, Univ of Georgia; Steven Frank, North Carolina State Univ; Peter Schultz, Virginia Polytech) and 6 temporary and permanent employees are responsible for collecting, sorting, counting and identifying the captured insects, maintain experimental records and equipment, record environmental factors and plant phenological events, and maintain sticky cards. The PIs are also responsible for developing educational materials and presentations for the training and educational workshops. TARGET AUDIENCES: The target audiences of this project include field and container nursery growers, landscape care professionals, arborists, municipal facility managers, and extension personnel. PROJECT MODIFICATIONS: Two modifications are proposed for the methodology of this project: 1. A beat-sheet sampling method will replace visual observations originally proposed for sampling predators associated with oak lecanium scale infestations. The beat-sheet method is a more reliable, easy and commonly used method in sampling for natural enemies. Visual observations will still be conducted to verify the consumption or attacks of the scale insects by the natural enemies. 2. Preliminary results indicated that the four pre-selected plant species do not provide sufficient correlation between plant pehnological events and scale insect phenological event. Observations suggested that the flower phenology of other plant species, such as southern magnolia, dandelion, honeysuckle and 'Knock-out' roses, are more closely correlated with the phenological event of oak lecanium scale. Therefore, it is proposed that the pre-selected hydrangea, crape myrtle, Loropetalum and day lily be replaced by these other plant species as phenological indicator plants. IMPACT: 2010/07 TO 2011/07 Egg hatch of oak lecanium scale was first observed in 11 May 2009, 10 May 2010 and 2 May 2011 in Florence, SC, which corresponds to 2823, 2404 and 2312 degree-days (DDs) at a base temperature of 35F, respectively. Egg hatch in Griffin, GA first occurred on 28 April 2011 or 2223 DDS, while in Raleigh, NC it was 11 May 2011 or 2106 DDS, and in Virginia Beach, VA it was 18 May 2011 or 2174 DDs; all at 35F base temperature. Based on results from 2011, the heat units required to reach egg hatch of oak lecanium scale is between 2106 and 2312 DDs, and did not appear to differ significantly among the different sampling locations or states. The final goodness-of-fit test to select the best-fitted degree-day models and base temperature (35-55F) will only be conducted at end of this project. The observed phenological events (initiation of flower bloom, 50% bloom, end of bloom) of the four pre-selected plant species did not correlate well with scale insect developmental progression. Southern magnolia was observed to be in full-bloom at Florence and Virginia Beach when egg hatch occurred. Plant phenological events that occurred at the same time include initiation of bloom of southern magnolia in Raleigh, full bloom of honeysuckle in Virginia Beach, and full bloom of dandelion and Knock-Out roses in Griffin. Preliminary results suggested that degree-day model may be a more reliable predictor of scale insect phenological event than plant phenological indicators. The selected plant species may also be replaced with other plant species, such as southern magnolia. A total of 36 parasitoid species, 6 coccinellid species, 2 neuropterans were associated with oak lecanium scale infestations in the four states. The natural enemies are being identified at this moment. Interestingly, a predator, Anthribus nebulosus (Anthribidae), released in 1970s against soft scales was captured in Virginia Beach during surveys in this project. Peak parasitoid abundance was recorded in Florence just before and after the period of egg hatch and crawler dispersal in May. Six presentations were provided at sic clientele workshops and education programs in SC in 2011 to disseminate information on the biology and management of oak lecanium scale (based on the results of this project) to about 165 nurserymen, landscape care professionals, arborists, homeowners, and extension personnel.

Outcomes N/A

Impacts From report submitted by the PI to USDA CRIS report system Egg hatch of oak lecanium scale was first observed in 11 May 2009, 10 May 2010 and 2 May 2011 in Florence, SC, which corresponds to 2823, 2404 and 2312 degree-days (DDs) at a base temperature of 35F, respectively. Egg hatch in Griffin, GA first occurred on 28 April 2011 or 2223 DDS, while in Raleigh, NC it was 11 May 2011 or 2106 DDS, and in Virginia Beach, VA it was 18 May 2011 or 2174 DDs; all at 35F base temperature. Based on results from 2011, the heat units required to reach egg hatch of oak lecanium scale is between 2106 and 2312 DDs, and did not appear to differ significantly among the different sampling locations or states. The final goodness-of-fit test to select the best-fitted degree-day models and base temperature (35-55F) will only be conducted at end of this project. The observed phenological events (initiation of flower bloom, 50% bloom, end of bloom) of the four pre-selected plant species did not correlate well with scale insect developmental progression. Southern magnolia was observed to be in full-bloom at Florence and Virginia Beach when egg hatch occurred. Plant phenological events that occurred at the same time include initiation of bloom of southern magnolia in Raleigh, full bloom of honeysuckle in Virginia Beach, and full bloom of dandelion and Knock-Out roses in Griffin. Preliminary results suggested that degree-day model may be a more reliable predictor of scale insect phenological event than plant phenological indicators. The selected plant species may also be replaced with other plant species, such as southern magnolia. A total of 36 parasitoid species, 6 coccinellid species, 2 neuropterans were associated with oak lecanium scale infestations in the four states. The natural enemies are being identified at this moment. Interestingly, a predator, Anthribus nebulosus (Anthribidae), released in 1970s against soft scales was captured in Virginia Beach during surveys in this project. Peak parasitoid abundance was recorded in Florence just before and after the period of egg hatch and crawler dispersal in May. Six presentations were provided at sic clientele workshops and education programs in SC in 2011 to disseminate information on the biology and management of oak lecanium scale (based on the results of this project) to about 165 nurserymen, landscape care professionals, arborists, homeowners, and extension personnel.

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