Search

The use of mulch in urban landscapes has increased in the United States for the past decade. Tree-based organic mulches can supply Coptotermes formosanus Shiraki with food, moisture, and shelter. The current research contributes to mulch management technology in termite control. A choice test arena was designed to determine the repellence and mortality caused by commercial mulches treated with different concentrations of the fungus Metarhizium anisopliae (Metschnikoff) against C. formosanus. Each of six tree-based mulches (pine bark, pine straw, bald cypress, eucalyptus, water oak, and melaleuca) was coated with six conidial concentrations ranging from 1 × 103 to 1 × 108 conidia/ml. The foragers of C. formosanus were repelled significantly by the fungal-treated mulch substrates; the proportion of termites on fungal-treated mulch was usually 99% of the termites were killed in test arenas containing a chamber with mulch treated with 107 or 108 conidia/ml. M. a...

Invasion of south Florida wetlands by the Australian paperbark tree, Melaleuca quinquenervia (Cav.) S.T. Blake (melaleuca), has caused adverse economic and environmental impacts. The tree's biological attributes and favorable ambient biophysical conditions combine to complicate efforts to restore and maintain south Florida ecosystems. Management requires an integrated strategy that deploys multiple biological control agents to forestall reinvasion and to supplement other control methods, thereby lessening recruitment and regeneration after removal of existing trees. This biological control program began during 1997 when an Australian weevil, Oxyops vitiosa (Pascoe), was released. A second Australian insect, the melaleuca psyllid (Boreioglycaspis melaleucae Moore), first introduced during 2002, has also widely established. After inoculation of the psyllid in a field study, only 40% of seedlings survived herbivory treatments compared with 95% survival in controls. The resultant defoliation also reduced growth of the surviving seedlings. A weevil-induced decline at a site comprised mainly of coppicing stumps had slowed after a 70% reduction. Psyllids colonized the site, and 37% of the remaining coppices succumbed within 10 mo. The realized ecological host range of B. melaleucae was restricted to M. quinquenervia; 18 other nontarget plant species predicted to be suboptimal or nonhosts during laboratory host range testing were unaffected when interspersed with psyllid-infested melaleuca trees in a common garden study. Evaluations are ongoing, but B. melaleucae is clearly reducing seedling recruitment and stump regrowth without adversely impacting other plant species. Manifestation of impacts on mature trees will require more time, but initial indications suggest that the psyllid will be an effective supplement to the weevil.

We studied the influence of herbivory by two introduced insect herbivores on the survival and performance of seedlings of Melaleuca quinquenervia (Cav.) Blake (Myrtaceae), an invasive tree that threatens the Florida Everglades ecosystem. Boreioglycaspis melaleucae (Moore) (Homoptera: Psyllidae) nymphs and Oxyops vitiosa (Pascoe) (Coleoptera: Curculionidae) larvae were transferred onto Melaleuca seedlings within replicated 0.25-m2 caged plots in Palm Beach County, FL. The treatments included three densities of Boreioglycaspis first instars at 1, 15, and 50 nymphs per seedling, one treatment of a single first Oxyops larval instar per seedling, another treatment of both one Oxyops larva and one Boreioglycaspis nymph per seedling, and caged and uncaged controls. Herbivory by Oxyops did not affect Melaleuca seedling height, leaf number, or survival. Feeding by Boreioglycaspis decreased survival, height, and leaf number, with these measures of plant performance ≈50% lower in the high and medium densiti...

We assess the geographic distribution and rate of spread of Oxyops vitiosa (Pascoe), a classical biological control agent of the invasive Australian tree Melaleuca quinquenervia (Cav.) S.T. Blake. This weevil has been released at 135 locations in south Florida, where it now occurs in 9 of 19 infested counties. When averaging dispersal distances among four representative sites, O. vitiosa spread at a rate of 0.99 (±0.28) km/yr, ranging from 0.10 to 2.78 km/yr. The rate of spread by O. vitiosa across melaleuca-dominated habitats was influenced by both ecological- and human-mediated parameters, including M. quinquenervia stand fragmentation (spatial separation among host plants), the number of weevils released, and time since release. The rate of spread was positively correlated with stand fragmentation level: high = 2.04, medium = 1.07, and low = 0.30 km/yr. By incorporating the dispersal rate from the highest fragmentation level into a simulation model we predicted that 138 months (June 2008) would be required for 50% of the habitat currently invaded by melaleuca to become infested at an economic weevil density (0.5 individuals per branch tip). At medium and low fragmentations, the model predicts 182 (February 2012) and 191 (November 2012) months, respectively. After examining the output from this basic model, we identified 16 possible redistribution sites that may accelerate the spread of the weevil.

The Australian paperbark tree, Melaleuca quinquenervia (Cavier) S. T. Blake, is a serious economic and environmental pest in Florida. One of the most damaging insects found attacking M. quinquenervia during surveys for biocontrol agents in its home range (Australia) was the leaf-blotching bug Eucerocoris suspectus Distant (Hemiptera: Miridae). Adults and nymphs of E. suspectus feed on young leaves and shoots. Their feeding kills leaf tissue surrounding the feeding site, leaving a distinctive, brown, blotch scar. Laboratory host-range studies showed 6 nontarget plant species to be at risk from E. suspectus. However, our extensive field survey data indicate that none of these plants are used as field hosts by E. suspectus. We conducted 8 intensive field searches for E. suspectus feeding damage on >60 plant species at 6 sites. Damage was only noted on Melaleuca spp., except on 1 occasion, where minor feeding damage was found on 2 Lumnitzera racemosa trees adjacent to a more heavily damaged M. quinquenervia tree. Thus, although E. suspectus completed its life cycle on several plant species in the laboratory (albeit at a much lower level than on M. quinquenervia ), in the field, feeding damage is restricted to Melaleuca spp. in the M. leucadendra (L.) L. complex, and rarely, Callistemon spp. The narrow host-range, broad habitat tolerances, and extensive damage caused by this insect should make it a valuable biological control agent if released in Florida.

The Australian tree Melaleuca quinquenervia (Cavanilles) Blake is an invasive weed in wetland systems of Florida. A biological control program targeting M. quinquenervia has resulted in the release of the gall forming midge Lophodiplosis trifida Gagné (Diptera: Cecidomyiidae). Populations of the introduced herbivore readily established at all 24 release sites across the weed's range in Florida, and there was no evidence that founding colony size (100, 2,000, or 6,000 adults) influenced herbivore establishment or local population growth rates. Landscape level spread of L. trifida from release sites averaged nearly 6 km/yr, ranging as high as 14.4 km/yr. Prerelease host range testing predicted that L. trifida oviposits indiscriminately on test plant species but does not complete development on any of the test species, including congeners present in Florida. To test the predictability of these host range tests, L. trifida was released in a common garden consisting of 18 test plant species that were interplanted with M. quinquenervia. Plant species postulated to be at risk experienced no gall development by L. trifida while intermingled M. quinquenervia trees supported 704.8 (± 158.5) galls per plant. Historically, many introduced Cecidomyiidae have limited effect on plant performance of target weeds because of recruitment of native parasitoids that disrupt biological control efficacy. In contrast to this trend, there has been no evidence to date that parasitoids are exploiting L. trifida in Florida.

The invasive tree Melaleuca quinquenervia (Cav.) Blake is widely distributed throughout peninsular Florida and poses a significant threat to species diversity in the wetland systems of the Everglades. Mitigation of this threat includes the areawide release campaign of the biological control agents Oxyops vitiosa Pascoe and Boreioglycaspis melaleucae Moore. We summarize the results of this release effort and quantify the resulting geographic distribution of the herbivores as well as their regional impact on the target weed. A combined total of 3.3 million individual Melaleuca biological control agents have been redistributed to 407 locations and among 15 Florida counties. Surveys of the invaded area indicate that the geographic distribution of O. vitiosa encompasses 71% of the Melaleuca infestation. Although released 5 yr later, the distribution of B. melaleuca is slightly greater than its predecessor, with a range including 78% of the sampled Melaleuca stands. Melaleuca stands outside both biological control agents' distributions occurred primarily in the northern extremes of the tree's range. Strong positive association between herbivore species was observed, with the same density of both species occurring in 162 stands and no evidence of interspecific competition. Soil type also influenced the incidence of biological control agents and the distribution of their impacts. The odds of encountering O. vitiosa or B. melaleucae in cells dominated by sandy soils were 2.2 and 2.9 times more likely than those predominated by organically rich soils. As a result, a greater level of damage from both herbivores was observed for stands growing on sandy versus organic-rich soils.