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Hydrilla verticillata. Plants parts on the right: a, reproductive turion; b, distinctly serrated leaf; c, underground tuber. (Drawn by W. Roux, first published in Henderson & Cilliers (2002), ARC-Plant Protection Research Institute, Pretoria.)
Source publication
Historically, biological control efforts against aquatic plants in South Africa have focused on
floating species, and as a result, there has been a dearth of research into the invasion and
control of submerged macrophytes. With numerous submerged invasive species already
established in South Africa, thriving horticultural and aquarium industries, n...
Context in source publication
Context 1
... verticillata (Fig. 2) is a perennial, rooted, submerged macrophyte (Cook & Lüönd 1982) with branching stems that form dense mats in many different types of freshwater habitats (Cook 2004). The plant is polymorphic and variable in its appearance which is highly dependent on the environmental conditions in which it grows (Cook & Lüönd 1982;Verkleij et al. ...
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Citations
... Of these, four have been released in the United States as biological control agents (Bennett & Buckingham 2000) and include two weevils, Bagous hydrillae O' Brien and B. affinis Hustache (Coleoptera: Curculionidae) (Buckingham & Bennett 1998;Balciunas et al. 1996), and two flies, Hydrellia balciunasi Bock and Hydrellia pakistanae Deonier (Diptera: Ephydridae). Hydrellia paki- stanae has been successful in the long-term management of H.verticillata in controlled experi- mentation and at field sites ( Doyle et al. 2002;Grodowitz et al. 2003), and is being considered for release in South Africa ( Coetzee et al. 2011) where H. verticillata was discovered in 2006 (Henderson 2006). An unidentified species of Hydrellia (Dip- tera: Ephydridae), recently identified from Brazil, has shown promise as a candidate agent for Brazil- ian water weed, Egeria densa Planch (Hydro- charitaceae), another submerged species that is becoming problematic in several countries world- wide (Cabrera Walsh et al. 2012). ...
The leaf-mining fly, Hydrellia lagarosiphon Deeming (Diptera: Ephydridae), was investigated in its native range in South Africa, to determine its potential as a biological control agent for Lagarosiphon major (Ridl.) Moss ex Wager (Hydrocharitaceae), an invasive submerged macrophyte that is weedy in many parts of the world. The fly was found throughout the indigenous range of the plant in South Africa. High larval abundance was recorded at field sites with nearly all L. major shoots sampled ontaining larvae, with densities of up to 10 larvae per shoot. Adults laid batches of up to 15 eggs, usually on the abaxial sides of L. major leaves. The larvae mined internally, leaving the epidermal tissues of the upper and lower leaves intact. The larvae underwent three instars which took an average of 24 days and pupated within the leaf tissue, from which the adults emerged. Impact studies in the laboratory showed that H. lagarosiphon larval feeding significantly restricted the formation of L. major side branches. Based on its biology and damage caused to the plant, Hydrellia lagarosiphon could be considered as a useful biological control candidate for L. major in countries where the plant is invasive.
... Many aquatic macrophytes are exotic, problem-causing species, including water hyacinth, red water fern (Azolla spp.), water lettuce (Pistia stratiotes), Kariba weed (Salvinia molesta), Hydrilla (Hydrilla verticillata) and parrot's feather (Myriophyllum aquaticum). Hydrilla is the latest addition to this list of problematic species, although its presence was already recorded in South Africa as early as 1963 (Coetzee et al., 2011b). ...
During the past 40 years, eutrophication has become an increasing threat to the usability of South African freshwater resources. Despite legislation moderating the discharge of phosphorus from some wastewater treatment works since the 1980s, eutrophication of freshwater resources is now widespread. Two important consequences are blooms of cyanobacteria, carrying the threat of cyanotoxin contamination, and excessive growth of macrophytes, which clog water-supply structures and reduce the recreational value of aquatic resources. Eutrophication-management options include reduction of phosphorus in detergents, biomanipulation of the food web, accurate prediction of cyanobacterial growth cycles, and mechanical disturbance of the epilimnion. The implementation of adaptive management to deal with eutrophication would ensure the testing and application of the most appropriate methodology to each eutrophic water body. Continued monitoring and reporting of trophic status are essential to establish whether interventions are having any effect.
