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United States Department of Agriculture

Agricultural Research Service


Location: Invasive Plant Research Laboratory

2011 Annual Report

1a. Objectives (from AD-416)
Culture melaleuca biological control agents in the glasshouse, screenhouse and nurseries and field release in various melaleuca infested areas in Miami-Dade County, assess their establishment and evaluate their impact on melaleuca populations.

1b. Approach (from AD-416)
Potted melaleuca plants will be raised in glasshouse, screenhouse and nurseries for use in culturing biocontrol insects. Colonies of the biocontrol insects (weevil, psyllids, and stem galling flies) will be be maintained in several walk-in screen cages. Healthy 4-6 ft tall branchy potted melaleuca plants will be introduced into the cages to allow the insects to transfer, establish and multiply on the plants for 2-3 weeks. Then these plants are enclosed in psyllid proof screens, number of adults per plant are estimated, transported to the field, plants are removed from the pots, root-ball is enclosed in a polythene bag filled with ca 5-gallons of water, and then placed in the melaleuca stands for the insects to be transferred to the adjacent melaleuca trees. This approach will be used for weevil and stem-gall insects as well. Establishment and their impact on release sites and other permanent plots will be monitored.

3. Progress Report
This research is related to inhouse objective 5: Release, establish, evaluate efficacy, and corroborate environmental safety of approved biological control agents and develop and distribute the technology to customers in order to expedite their adoption and deployment. This year’s (May 26, 2010 thru May 25, 2011) releases were concentrated in Wellfield and their surrounding areas based on the suggestions from the Miami-Dade Department of Environmental Resources Management (DERM). Of the total 23 sites identified as wellfields, four (Newton, West, South-west and North-west) contain substantial populations of melaleuca while remaining areas were occupied either by the agricultural fields or neighborhoods and had no detectable melaleuca infestations. Survey of melaleuca invaded Wellfields and other sites in Miami-Dade County showed varying densities of biological control insects (weevil, psyllid, cecid) and an adventive foliar rust fungus (Puccinia psidii) inciting damages to the melaleuca population trees. During this reporting period we reared in screenhouse, collected from field and made 40 releases accounting for a total of 308,094 psyllid and 4,591 weevil individuals. The four wellfields: Newton, West, South-west and North-west received 20204, 200598, 8992, and 82891 individuals, respectively. During the spring of 2011 we evaluated long-term study (15-yr) plots maintained and monitored as the part of melaleuca biocontrol impact assessment program in southeastern Florida. Data revealed continued decline of melaleuca stand density leading to the significant return of native plants such as sawgrass, dahoon holly, Guiana rapanea, wax myrtle and others; these species have dominated second canopy underneath sparsely populated melaleuca trees. There is significant reduction in the number of fruit bearing melaleuca trees due to chronic damage of new flush destined for flower production. The biological control agent production, release, and establishment activities are directly monitored by principal investigator thru regular supervision and monitoring of biocontrol insect production facility and release sites.

4. Accomplishments

Last Modified: 06/24/2017
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