Location: Invasive Plant Research Laboratory2010 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 relates to the inhouse objective: Prioritizing and evaluating suitable target species for control; conducting surveys to discover natural enemies; studying the ecology of target species and determining the impact of their suppression on ecosystems; conducting risk analysis of potential biological control organisms; and releasing, establishing, evaluating, and transferring biological control agents against target species. Survey of melaleuca invaded sites in Miami-Dade County showed varying densities of biological control insects such as weevil and psyllid and an adventive foliar rust fungus (Puccinia psidii) inciting damages to the melaleuca population trees. Most of the melaleuca stands in Chekika areas of the Everglades National Park appeared to have lower densities of these natural enemies. Similarly, many melaleuca stands spotting undeveloped public and private lands south of Homestead-Miami Speedway and around Old-Dixie Highway (Old Card Sound Road) areas were virtually devoid of psyllids though a very low level of weevil damage was observed. Therefore, these sites were primarily targeted for psyllid and weevil redistribution during 2009-2010; these sites and others in selected areas that are deemed to have lower densities will be targeted during 2010-2011 also. During this 2009-2010 reporting period, we made a total of 34 releases totaling over 799,494 psyllids and 4,522 weevils within various melaleuca stands in these areas of Miami-Dade County. During this reporting year we concluded a long-term study designed to assess possible effect of melaleuca litter biomass on its native community invading potential and determined that slow decomposing rate of melaleuca leaves compared to sawgrass may be resulting in an accumulation of excessive amount capable of impeding recruitment of native plants. Also, we have been continuing to monitoring research sites maintained to determine the recovery of melaleuca sites and increasing site dominance by other plant species. The biological control agent production, release, and establishment activities are directly monitored by ADODR thru one to two visits (per month) of psyllid production facility and release sites. Miami-Dade DERM’s continued financial support towards melaleuca biocontrol efforts of this laboratory has been extremely valuable.